Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

APC - JC > Building Pathology > Flashcards

Building Pathology Flashcards

1
Q

What are causes of damp?

A
  • External: drainage defects, defective rainwater goods, roof leaks, flooding. Moisture enters masonry walls where it can move around.
  • Internal: plumbing leaks, debonding / damages to finishes, high atmospheric moisture, condensation
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

How would you investigate damp?

A
  • Visual investigation
  • Inspection using protimeter – resistance meters can read high as soluble salts on the wall surface permit electrical conductivity even if the wall is dry.
  • Intrusive inspection e.g. drilling into masonry, use of humidity boxes, taking up floorboards / skirting
  • Speedy moisture meter – aluminium flask w/ pressure gauge – insert sample and add carbide. Moisture in sample reacts w/ carbide to form acetylene gas, giving pressure reading calibrated to give %MC. Brick / masonry readings over 2% require further investigation
  • Thermal imaging cameras – can show pattern of water spread throughout walls / floors / ceilings. Shows difference in temperature
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

When was the Georgian era?

A
  • 1714 – 1830
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

When was the Victorian era?

A
  • 1837 - 1901
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

When was the Post war era?

A
  • 1945 – 1979
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What typical defects would you encounter in the post war era?

A
  • Cut edge corrosion
  • Damp
  • Concrete defects, carbonation, HACC, ASR, Sulphate Attack
  • Brick slips
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

UoL Roof Survey - What did the client instruct you to do?

A
  • Undertake a condition survey of the roof in order to provide a specification of repairs
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

UoL Roof Survey - Roofing condition survey methodology

A
  • Sketch area of the roof level, taking measurements
  • Noting defects to all areas, including roof covering, upstands, hard standings (paving slabs), parapet walls
  • Taking photographs of the areas and detailed notes to include in my report
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

UoL Roof Survey - What did you check when undertaking your site inspection

A
  • Condition of the roof coverings, etc.
  • Access routes to the building (central London) – assumed parking licenses required for works
  • Safe access – requirement for scaffolding
  • Location of compound and storage of materials
  • Internal inspection to affected rooms below
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What are typical defects of a 1970s concrete building?

A
  • Carbonation
  • High Alumina Cement Concrete (HACC)
  • Alkali-silica reaction (ASR)
  • Spalling
  • Cracking
  • Blistering
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

UoL Roof Survey - What was the build-up of the roof?

A
  • Concrete roof deck - screeded
  • 20mm mastic asphalt applied directly onto screeded deck
  • Liquid waterproofing system
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

UoL Roof Survey - Why was replacement of the roofing cover proposed and not patch repairs?

A
  • Various patch repairs including applied liquid across much of the building
  • Internal damage was so that severe deterioration present across roof level
  • Roofing covering original –(1970s) so beyond its lifespan / economical repair
  • 25-year guarantee of new roof covering will greatly reduce maintenance costs
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

UoL Roof Survey - Why was a liquid system specified?

A
  • Roof area was circa 1,700sqm – liquid less labour intensive to apply over large areas
  • Superior waterproofing over felted system
  • Easy application
  • Building was in centre of London, so minimised space required to store materials
  • Allowed application in hard to reach areas – plant/tank houses were on raised platforms on the roof level
  • Fully bonded to substrate, so no glow paths for water
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

UoL Roof Survey - Why did you specify to include insulation?

A
  • According to Part L, consequential improvement stipulates you must increase thermal efficiency in line with building regs – 0.16W/m2K
  • No insulation present, so roof likely to be poorly performing in respect to thermal retention
  • To improve the thermal performance of the roof and improve the U-value
  • Consequential improvement - when replacing 50% or more of a roof covering, it needs to be brought up to Part L standards
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

UoL Roof Survey - Why did you allow the roofing specialist to specify the works?

A
  • To obtain an insurance-backed guarantee of the works for 25-years
  • Ensure contractor undertakes installation in line with the guarantee
  • Roofing specialist will check each section of works and sign them off
  • Liability falls on the roofing specialist
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

UoL Roof Survey - what was the proposed build-up?

A

Bottom up:
1. Roof deck
2. Primer
3. VCL
4. Insulation adhesive
5. 120mm insulation
6. Synthetic spray-on primer
7. Bituminous waterproofing membrane
8. Reinforcement fleece
9. Waterproofing liquid top coat

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

UoL Roof Survey - What are the building regs / building standards a liquid system should be installed to?

A
  • BS 8217:2005 -waterproofing
  • BS EN ISO9002 – insulation
  • Upstands (minimum 150mm height) – BS 6226
  • Building regulations:
    o Part B – fire safety
    o Part L – conservation of fuel and power
    o Part 7 – materials & workmanship
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

UoL Roof Survey - Why did the existing roof fail?

A
  • Roof was subject to blisters which occurs when the asphalt expands and pops through the surface due to higher temperatures in summer
  • Crazing / cracking across the roof level allowing moisture into the rooms below
  • Cracking to upstands
  • Failure of patch applied liquid coatings
  • Lack of maintenance throughout roof’s lifespan
  • UV degradation over many years
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

UoL Roof Survey - What other measures did you consider?

A
  • Installing a felted roof, however was deemed as more labour intensive, various areas of plant / machinery on roof mean felt detailing much more difficult to achieve
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

UoL Roof Survey - What is the minimum requirements for roof replacement?

A
  • 150mm upstand height
  • 120mm insulation if included – to meet 0.16W.m2K U-value
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

UoL Roof Survey - What internal repairs did you recommend?

A
  • Internal plaster repairs – single layer of Gyproc to ceiling
  • Replacement of ceiling tiles as was suspended ceiling
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

OFS - What advice did you give immediately?

A
  • After initial inspection, I recommended a structural engineer visit to assess the building
  • Client had already erected emergency scaffold to protect against falling roof tiles
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

OFS - Why did you think a structural engineer was required?

A
  • To confirm condition of steel filler joists and parapet walls in respect to their structural integrity, and recommendations for repairs.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

OFS - What recommendations did you confirm with the structural engineer?

A
  • Rebuilding works to parapet walls
  • Replacement to flat roofs incorporating new insulated timber joist installation
  • Replacement of pitched roof coverings
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

OFS - How did you propose to rebuild the parapet walls?

A
  • Protect internal rooms an ensure no water ingress – top hat scaffold
  • Remove soldier course down to top layer of brickwork
  • Remove creasing tiles and mortar
  • Carefully take down brick courses to an acceptable level – i.e. a safe level that is structurally sound
  • Install new brickwork to match similar – key in with matching mortar – NHL 3.5
  • All soldier course brickwork to be mechanically fixed and installed using NHL 5 mortar
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

OFS - How did you propose to rebuild the flat roofs?

A
  • Use top hat scaffold and ensure provision of night joints
  • Break out and strip asphalt from roof and upstands
  • Break out clinker concrete slab
  • Safely remove filler joists
  • Install insulated timber joists (48mm x220mm), 400mm centre, fix into new brickwork using hard packing such as slate to bed into mortar
  • Joists placed onto timber wall plate bedded into the mortar and strapped down
  • Ensure joists have minimum bearing of 90mm and provide restraint straps at 2m centres where joists run parallel to walls
  • Install exterior grade plywood deck 18mm thick
  • New waterproof system – 3layer with insulation
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

OFS - How did you propose to replace the roof tiles?

A
  • Remove defective tiles using a roof ripper
  • Remove battens
  • Check integrity / condition of timber frame
  • Remove sarking felt and replace
  • Nail each tile into the battens and ensure appropriately fixed
  • Fix ridge and hip tiles on with NHL 5 mortar
  • Install code 4 lead flashing
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

OFS - What is NHL mortar?

A
  • Natural hydraulic lime, measured in compressive strength N/mm2 (Newtons per sqmm)
  • NHL 2 – soft, permeable, minimal exposure to weather e.g. internal brickwork, hydraulic lime plaster, chalky stones
  • NHL 3.5 – medium density, moderate weather exposure e.g. bricks, facings, blockwork, pointing
  • NHL 5 – dense, impermeable, severe exposure e.g. roofing, chimneys, parapets
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

OFS - What codes of lead flashing are there?

A
  • Code 3: 1.32mm thick, 14.97kg/m2 – used for soakers
  • Code 4: 1.80mm, 20.41kg/m2 – apron flashing, valley gutters, dormers
  • Code 5: 2.24mm, 25.40kg/m2 – flat/pitched roof flashing, dormers
  • Code 6: 2.65mm, 30.10kg/m2 – as above, not used for soakers or vertical cladding
  • Code 7: 3.15mm, 32.72kg/m2 – most durable for pitched roofs
  • Code 8: 3.50mm 40.26kg/m2 – used on flat roofs parapets, valleys, not suitable for flashing
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

OFS - What bricks make up the OFS?

A
  • London stock bricks
  • Mortar is flush so to allow rain to drain off the surface and not be encouraged to soak into the wall as with recessed or struck pointing
  • Sizes:
    o Imperial 2 ¾ x 9 x 4 1/4 “ – 68 x 230 x 110mm
    o Metric 65 x 215 x 102.5mm
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

OFS - How did you know the building was Victorian?

A
  • Solid masonry construction
  • Ornate features such as corbelling, cornicing, banding across the elevation
  • Steep pitched roofs
  • Timber sash windows with panes
  • Date stone stated it was 1898
  • Rear mansard roof
  • Octagonal tower originally used to dry hoses for the fire station, but has since been capped off
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

OFS - What is the composition of a load-bearing masonry wall?

A
  • Made of brickwork with lime mortar
  • Solid wall – 2 brick thick
  • Supports vertical loads above – i.e. the upper floors of the building
  • Provide separation internally for each different room, allowing loads to transfer from other parts of the structure to foundations
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

OFS - How did you know there were filler joists / clinker concrete?

A
  • Upper flat had extensive water damage whereby concrete casing to the joists had fallen away exposing the joists
  • Loose concrete had fallen away
  • Exposed steel was corroded
  • I instructed opening-up works to parapet walls and internally
  • Initial assumption due to the age and type of the building
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

OFS - What are the issues with coke breeze and filler joint construction?

A
  • Developed as a method of constructing fire proof floors, the system uses parallel steel joists with an infilling of breeze concrete.
  • Breeze has a high sulphur content, which in moist conditions produces sulphuric acid. Steel embedded in breeze has an acute risk of severe corrosion
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

OFS - Where would you find filler joint construction?

A
  • Typical locations are upper floors of factory premises constructed in the late 19th and early 20th centuries.
  • Also found in public buildings, banks, hospitals, schools and some housing schemes.
  • Long cracks along the joists at approx 600 to 900mm centres
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

OFS - What are the remedies for the steel joists?

A
  • Localised breaking out and coating with resin repair systems
  • Replacement of the joists where serious section loss has occurred.
  • Regular inspection and keeping the joists dry
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

OFS - What were the typical defects in this instance?

A
  • Loss of section to steel filler joist, opening up works deemed it structurally inadequate
  • Cracking to parapet walls in north east and south west of building
  • Cracking and loose coping stones
  • Corrosion following water ingress – this can allow the steel to expand and crack the concrete
  • Water ingress occurred due to porosity of the clinker concrete
  • The corrosion caused cracking and pushed the concrete encasement outwards
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

OFS - What treatment / repairs were considered for the joists?

A
  • Vacuum injection of resin – encapsulates steel beams and protects against future corrosion
    o A – allows concrete to stay in place – non-invasive
    o A – quick to apply and cure
    o D – concrete was severely cracked so removal of defective concrete only option
  • High-pressure water jet to blast off the corrosion
    o A – easy to use
    o D – not necessarily powerful enough to remove tough corrosion layers
    o D – causes a lot of water spillage – not suitable for internal use
  • Sand blast to remove corrosion
    o A – easy, efficient and time-saving over sanding
    o A – powerful, able to remove tough layers of corrosion
    o D – can cause a lot of dust / air pollution – not suitable for internal use, generally very messy
    o D – can cause injury due to rebounding materials
  • Chosen repair – sanding / cleaning to ST2 standard using thorough scraping with a wirebrush and cleaned with vacuum cleaner
    o Why – exposed section was relatively small, less costly and corrosion not significant enough to warrant sandblast or pressure jet. Once completed, specified to coat steel in paint to provide barrier against future moisture
    o What is ST2 – “thorough hand cleaning” surface free from visible oil, grease, dirt, rust and paint coating.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

OFS - What are other ST types of cleaning?

A
  • Blast cleaning:
    o Sa 1 - Light blast cleaning – jet passes rapidly over surface to remove loose mill scale, rust
    o Sa 2 – thorough blast cleaning – jet passed over long enough to remove all mill scale and rust and practically all foreign matter. Surface then cleaned with vacuum, clean and dry compressed air or a clean brush
    o Sa 2.5 – very thorough blast cleaning – mill scale, rust and foreign matter removed that only remnants appear as shades. Surface then cleaned with vacuum
    o Sa 3 – blast cleaning to white metal – jet removes all mill scale, rust and foreign matter. Surface cleaned with vacuum cleaner leaving uniform metallic colour
  • Manual scraping / wirebrushing
    o St 2 – thorough scraping with hard metal scraper, removing all scale, rust and foreign matter. Cleaned with vacuum, leaving faint metallic sheen
    o St 3 – extremely thorough scraping, surface prep for St 2 but more accurate. Surface should have pronounced metallic sheen
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

What are the key features of a Georgian Building?

A
  • Symmetrical, square buildings
  • Roofs and gutters set behind parapet walls
  • Stucco render to imitate stonework
  • Large sliding sashes with 6x6 panes of glass
  • Fanlights above the front door
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
41
Q

What are common defects of Georgian Buildings?

A

– Water ingress through parapet walls, valley gutters
- Decayed timber to floor joists: can be poor cross ventilation to floor voids in long narrow terraces.
- Failure of roof trusses when roof ties rot due to past unknown bomb damage.
- Missing or poorly altered load-bearing timber partitions.
- Damp basements.
- Poorly applied / painted stucco plaster preventing moisture escape.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
42
Q

What are typical causes of deflecting/bouncy timber floors?

A
  • Over notching of joists
  • Removal of herringbone strutting
  • Loss of end bearings
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
43
Q

What is Herringbone Strutting?

A
  • Timber installed between joists in a cross position and tightened with folding wedges.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
44
Q

When was the Victorian period?

A
  • 1837-1901
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
45
Q

What are the features of Victorian Buildings?

A
  • Ornate features such as corbelling, cornicing, banding across the elevation
  • Steep pitched roofs
  • Mansard roofs
  • Timber sash windows with 6x4 panes
  • Ground floor bay windows
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
46
Q

Typical Defects in Victorian buildings?

A
  • Rising damp/failed or bridged DPC
  • Cracking to bay window junctions.
  • Lead pipework.
  • Poor ventilation of sub floors due to blocked air vents from removal / riaisng of external pavement level
  • Corrosion of filler joists
  • Wet/Dry rot/timber decay
  • Blocked/damaged cast iron rainwater goods
  • Defective roof slates and nail sickness
  • Roof spread - sagging roof timbers, can be due to replacement of slates with cheaper / heavier cement or clay tiles
  • Differential settlement of part basements in terraces.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
47
Q

What’s a Bressumer beam?

A
  • Large timber beams supporting the surrounding structure, typically found above bay windows.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
48
Q

What could cause cracking at bay window junctions?

A
  • Differential movement between the shallower foundations of the bay and the main building.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
49
Q

Typical Defects in interwar properties?

A
  • Cavity wall tie failure
  • Concrete defects, HACC, Carbonation, ASR, Sulphate Attack
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
50
Q

Typical defects in post-war properties

A
  • Use of deleterious materials,
  • HACC, Carbonation, ASR, Sulphate Attack, Chloride attack
  • Asbestos
  • Cavity wall tie failure
  • Cut edge corrosion
  • Clay pot flooring
  • Woodwool Slabs
  • Use of boot lintels and finlock gutters.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
51
Q

Typical Defects in commercial property

A
  • Cut edge corrosion
  • Carbonation
  • HACC
  • Brick slips
  • Wall tie failure
  • Blocked/damaged rainwater goods.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
52
Q

What non-invasive investigative techniques are you aware of?

A
  • Infrared thermography
  • Electronic leak detection
  • Search mode on damp meters
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
53
Q

What is Hydraulic Lime Mortar?

A
  • Set by hydrolysis, a reaction caused by water.
  • Causes a faster, harder set and more suitable of exterior work in exposed or damp conditions.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
54
Q

What is non Hydraulic Lime?

A
  • Putties set by carbonation, causes a much slower set and lime remains softer and breathable.
  • Produced by slaking quicklime in an excess of water and left to mature for at least three months
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
55
Q

What does NHL 3.5 mean?

A
  • Natural hydraulic lime
  • Achieves a compressive strength of over 3.5MPa (mega pascal) at 28 days
  • Suitable for bedding and pointing.
  • NHL 5 mortar – suitable for ridge tiles, roof tiles, parapets – brickwork generally more exposed to the elements
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
56
Q

Where would you specify non hydraulic lime?

A
  • Use with cob, strawbale, timber frames and soft bricks and stone.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
57
Q

Where would you specify Hydraulic Lime?

A
  • Use with hard brick or stone
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
58
Q

What is a deleterious material?

A
  • Materials that are dangerous to health, causes failures in buildings or are environmentally damaging, not suitable for their intended use and pose a risk where they have been used
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
59
Q

What are some examples of deleterious materials?

A

– Asbestos
- Lead paintwork/lead pipework
- RAAC
- Wood Wool Slabs
- High Alumina Cement
- Brick Slips
- Filler joists
- Clay pot flooring

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
60
Q

What deleterious materials are you aware of in mechanical building systems?

A
  • Polychlorinated Biphenyls (PCBs)
  • R22 Refrigerants
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
61
Q

What are PCBs?

A
  • Used since 1929 in cooling fluids, grouting and sealants, insulation and dialectic fluid.
  • Banned in 1981 in new equipment, closed uses in existing equipment above 5 litres was not banned until 2000.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
62
Q

Why were PCBs Banned?

A
  • Carcinogenic, damages health of humans, environment and animals
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
63
Q

What are R22 refrigerants?

A
  • Used in air conditioning and refrigeration systems pre-dating 2004, was banned in new equipment in 2004 and refurbished systems since 2015.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
64
Q

Why were R22 refrigerants banned?

A
  • Banned due to the effects on the ozone layer by the EU
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
65
Q

When were brick slips used?

A
  • Popular in 1960s and 1970s as a method of concealing the exposed edges of a concrete frame.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
66
Q

What are the issues with brick slips?

A
  • Risk of poor adhesion due to shrinkage.
  • Lack of soft joints can transfer load to slips and cause delamination.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
67
Q

How would you identify the brick slip failure?

A
  • Splitting and spalling brickwork along horizontal joint positions at each storey
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
68
Q

What are RAAC Planks?

A

– Introduced in 1950s, production stopped in 1982
- Reinforced Autoclaved Aerated Concrete
- Used in the construction of lightweight thermal blocks for buildings
- The planks were often used as roof decks, floors and internal partitions.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
69
Q

When were they introduced into the UK?

A
  • In 1995 in schools, concerns were raised over the durability and integrity of the planks when surface cracking was discovered
  • Investigations by the BRE lead them to conclude RAAC had a life expectancy of 30 years
  • Particular concerns were raised over the strength of the planks when coated with bitumen coated reinforcement, test panels have failed suddenly at low deflection.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
70
Q

What are the typical defects to look out for?

A
  • Crushing of the bearing ends
  • Corrosion of light steel reinforcement
  • Transverse cracking on the soffit
  • Slippage of reinforcement under load, slippage could lead to deflection
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
71
Q

Following identification of RAAC, what checks would you undertake?

A
  • Check for cracking on the soffit
  • Check for deflection in the planks
  • Determine the age of the structure – planks used in 1980 are more susceptible
  • Check condition of roof coverings – leaks could encourage corrosion of the reinforcement
  • Check bearing widths, if less than 40mm seek advice
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
72
Q

What would you advise having identified RAAC planks?

A
  • If sound, inspect every 5 years, or if located in a harsh environment check each year
  • Reduce dead loads by removing stone chippings, plant etc.
  • Check for transverse cracking and measure the deflection of the slabs.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
73
Q

Why were hollow clay pot floors used?

A
  • Used in the early part of the 20th century as a means of constructing fire proof floors and reducing dead loads. Declined in 1970s, production stopped in 1980s.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
74
Q

What were the issue of hollow clay pot flooring?

A
  • If reinforcement was poorly positioned, aggregate too large or the concrete poorly compacted, there would be a risk of honeycombing of the concrete ribs.
  • This would lead to a loss of fire resistance, durability or strength.
  • Due to the use of tile spacers, inspection of the concrete ribs could not be undertaken.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
75
Q

What are the issues with woodwool slabs?

A
  • When used as permanent shuttering for in-situ concrete, results in honeycombing or voiding within the concrete. May lead to reduced fire resistance or, in extreme cases, loss of structural strength.
  • Concrete does not adequately get compacted.
  • Risk of poor cover to the steel and hence loss of durability, possible reduction in strength, and loss of fire resistance.
  • Voiding and honey combing due to vibrations. Poor bond or failed bond between the wood wool and the hardened concrete.
  • Buildings constructed from 1950 to the mid-1970s are most likely to be affected by this form of construction.
  • If permanent shuttering is discovered, intrusive investigations may be needed to determine the adequacy of concrete cover to the steel reinforcement. If voiding is present, the affected area can be exposed and repaired using hand-fixed concrete repair methods or, if over a larger area, sprayed concrete.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
76
Q

Wood wool slabs are deleterious materials. Explain why and where their use would be acceptable

A
  • When used as permanent shuttering for concrete, it may lead to grout loss, honeycombing or voids which can reduce fire resistance, corrosion protection and loss of strength. It is adequate for use in flat roof decking.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
77
Q

What is Strammit?

A
  • Lain for Straw
  • Trade name for compressed strawboards made from wheat by a patented process using the natural cellulose as a self-binding resin.

Used for:
- Used post WWII as it was affordable, easy to manufacture and install and had good thermal properties (for the time)
- The exterior of the strawboard was boned with paper for roof decks, the overall thickness generally ranges from 35mm to 60mm.
- Can be found in walls, ceilings, floor and roof decks

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
78
Q

What was the typical flat roof construction using Strammit?

A
  • Strammit supported on joists
  • Covered with bitumen felt with a top surface of stone chippings
  • Joints in the board were meant to be taped with bitumen scrim
  • Strammit was usually lined with building paper to withstand showers until the waterproofing layer was installed.
  • The building paper lining the boards may contain asbestos
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
79
Q

Why is Strammit deleterious?

A
  • They lose structural capacity after becoming wet
  • Interstitial condensation and leaks causes the resins to break down, this deterioration is irreversible
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
80
Q

Where you identify Strammit board, what would your advice be?

A
  • Advice that the roof should not be walked on in any circumstance.
  • Additional loading should not be imposed.
  • Strawboard is defined as fragile in HSE Guidance.
  • Consideration of replacing the roof within the short term.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
81
Q

What considerations would you have when advising to replace a strammit roof?

A
  • Suitability of the new roof to resist the passage of moisture and be suitable for the span and loadings.
  • Thermal and acoustic insulation (building control)
  • Interface with abutments
  • Drainage and falls
  • Internal works, services, lighting etc.
  • H+S, asbestos, crash decks
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
82
Q

What types of damp are you aware of?

A
  • Rising
  • Penetrating
  • Condensation
  • Pipe leaks
  • Flooding
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
83
Q

What is the typical moisture content of internal joinery in building with heating?

A
  • 9 – 13% - dry
  • 17-20% - at risk
  • 20% or more - wet
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
84
Q

When would bricks be considered damp?

A
  • With a moisture content of between 2% and 3%
  • Engineering bricks could be considered very wet at 2%
  • The porosity of a fletton brick would be considered damp at 2%
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
85
Q

How would you confirm whether a brick was saturated?

A
  • Based on the material of the brick
  • Manufacturers provide information on the PMC (potential moisture content)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
86
Q

Take me through your survey methodology when undertaking a damp inspection?

A
  • Speak to the occupiers or those who have knowledge about the building and the issues
  • Map the area of concern in a basic sketch
  • Inspect for obvious causes and note what is or isn’t happening
  • Collect evidence
  • Eliminate the suspects, factors that may cloud the cause
  • Determine the source
  • Consider basic remedies i.e. get water/moisture away faster, stop water spreading, and reduce moisture being created.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
87
Q

What other information may be important for a damp survey?

A
  • Age of the building
  • Wall construction
  • Fenestration details
  • Locations of window or wall vents above and below flooring
  • Mechanical ventilation and type
  • Locations of damp and mould
  • Locations of external defects i.e. defective rainwater goods
  • Floor construction
  • Heating
  • Roof type
  • Occupation level
  • Internal environment conditions
  • Types of drainage
  • Local water table
  • Internal plumbing checks
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
88
Q

What is relative humidity?

A
  • The amount of water vapour in the air expressed as a percentage of the amount needed for saturation at the same temperature.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
89
Q

What is a dew point?

A
  • The point at which water vapour will condense into liquid form.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
90
Q

What is hydrostatic pressure?

A
  • Pressure created by a head of water, for example in a basement where the water table is well above the basement floor level.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
91
Q

How can moisture move through materials?

A
  • Vapour pressure diffusion – When air on one side if a wall is at a different vapour pressure (moisture content) to air on the other, moisture moves until both sides are at equilibrium,
  • Capillary Action – Water moves through water tension
  • Hygroscopicity – Substances attract water from the air (salts)
  • Hydrostatic pressure
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
92
Q

What is equilibrium moisture content (EMC)?

A
  • The point at which a material will neither gain or lose moisture
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
93
Q

Why is moisture in buildings an issue?

A
  • It expands and contracts with fluctuating temperature, causing cracks and degradation to materials
  • Enables mould to grow.
  • It can lead to attacks from wood boring insects which are attracted to damp timber
  • Damp timber can be subject to dry or wet rot
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
94
Q

What is rising damp?

A
  • Ground water rising through a wall through capillary action.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
95
Q

What BRE Digest relates to rising damp?

A
  • BRE Digest 245
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
96
Q

What factors can affect the height water can reach?

A
  • The height of the water table
  • Surface and subsoil drainage
  • The rate of evaporation
  • The presence of a damp-proof course (DPC)
  • DPC bridging
  • The wall finishes
  • Wall thickness
  • Presence of salts
  • Water/moisture entering the wall from above ground
  • The application of non-breathable materials
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
97
Q

What are the symptoms of rising damp?

A
  • Deterioration of internal finishes
  • Musty Smell
  • Tide marks to 1m
  • Rotting of internal timber
  • Hydroscopic salts
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
98
Q

What are the typical causes of rising damp?

A
    • Missing or defective DPC
  • DPC being bridged externally – e.g. ground installed above DPC
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
99
Q

When did it become a requirement for buildings to be provided with a Damp Proof Course?

A
  • The Public Health Act 1875
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
100
Q

What are the options for remedying rising damp?

A
  • Installation of a physical DPC
  • Reduction in height of external ground levels
  • Chemically Injected DPC
  • Additional Land Drainage
  • Fixing broken drains
  • Internal tanking
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
101
Q

What is the purpose of a DPC?

A
  • Prevent moisture soaking up through the ground.
  • Acts as a barrier to water entering the wall.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
102
Q

What are common causes of damp course failure?

A
  • Structural movement fracturing brittle damp course
  • Light degradation of polythene membranes during construction
  • Design error in cavity trays or stepped damp courses
  • Incorrect ground levels close to damp course
  • Bricks laid frog up and no mortar bed below damp course
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
103
Q

What is the process of inserting a chemically injected DPC?

A
  • A resin is injected 150mm above ground level at regular intervals, at 100mm to 150mm centres
  • The chemicals act as pore liners, preventing capillary movement of moisture.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
104
Q

What additional works may be undertaken to treat rising damp?

A
  • Hacking off internal wall plaster
  • Drying out of masonry where exposed
  • Replaster with a waterproof render
  • Reinstatement of skirting, fixtures and fittings.
105
Q

What would you consider before chemically injecting a DPC?

A
  • Cost
  • Disruption
  • Suitability
  • Reliability
106
Q

What types of chemical DPCs are you aware of?

A
  • Pressure injection
  • Gravity transfusion
  • Injection mortar
  • Injection creams
107
Q

What are the advantages and disadvantages of chemical DPCs?

A
  • Advantages
     DPC will be provided with a guarantee
     Injection works can be undertaken externally
     Damp proofers will be able to start work quickly
  • Disadvantages
     Disruption when replastering
     Will be cheaper than physical DPC insertion
     Dense plasters may stop the wall breathing
108
Q

What would the testing of salts tell you?

A
  • Presence of nitrates and sulphates may indicate the presence of ground water
  • However this is unreliable, reference to water testing has been removed from BRE guidance since 2007.
109
Q

What is the British standard for tanking/structural waterproofing?

A
  • BS 8102: 2009
110
Q

What are the grades of structural waterproofing?

A
  • Grade 1 – Basic utility – e.g. car parks
  • Grade 2 – better utility – e.g. plant rooms, workshops
  • Grade 3 – habitable – residential
  • Grade 4 – Special – archive storage
111
Q

What are the three types of water resistant construction?

A
  • A – Barrier (membrane) protection
  • B – Structural integral protection
  • C – Drained protection
112
Q

What could the possible causes of penetrating damp?

A
  • Cracked or defective rendering
  • Deteriorated pointing
  • Blocked, damaged or inadequate rainwater goods
  • Defective flat and pitched roof coverings including upstands and weathering’s.
  • Blocked cavity wall voids
  • Raised external ground levels
113
Q

How do you identify penetrating damp?

A
  • Damp staining of external walls
  • Damp patches on walls / ceilings
  • Wet / crumbly plaster
  • Signs of spores or black mould isolated to one area
  • Drips and puddles
114
Q

How could a DPC be bridged?

A
  • Raised ground levels externally
  • Poor detailing of retrofitted floors, unlinked DPM and DPC
  • Render extending below DPC level
  • Mortar droppings in the cavity
115
Q

How do you remedy penetrating damp

A
  • Ensure removal of source of moisture
  • Repairs to defective rainwater goods
  • Repair / replacement of rendering – ensuring appropriate mortar mix to key into brickwork
  • Replacement of roof coverings where necessary
  • Repointing of brickwork – rake out to a depth equivalent to their height
  • Waterproofing brick walls – e.g. with masonry protection cream which ensuring brickwork pores are lined, not blocked, so the masonry can breathe
116
Q

When does condensation occur?

A
  • When water vapour in the air comes into contact with a cold surface it reaches the dew point, this causes the water to condensate on the cold surface.
117
Q

What is cold bridging?

A
  • When a warm surface or structure meets a colder one
  • A weak spot in insulation where there is a break in the continuity of the insulation – e.g. between rafters
118
Q

What is the British standard for condensation control?

A
  • BS5250: 2011
119
Q

What are the 4 types of condensation listed in the standard?

A
  • Surface condensation – normal condensation on cold spots etc.
  • Interstitial condensation – condensation occurs within the layers of the building envelope
  • Reverse condensation – a form of interstitial condensation, where vapour moves through solid masonry walls and forms on the inside of the vapour check if the wall is insulated internally.
  • Radiation condensation – another form of interstitial condensation, it occurs when the atmosphere rapidly loses heat which causes condensation on the underside of building materials i.e. garage roof sheeting.
120
Q

What are the common causes of condensation?

A
  • Inadequate ventilation
  • Drying clothes internally
  • Cooking, breathing, overcrowding
  • Type and level of heating
  • Poor air circulation internally
  • Design, layout and form of construction
  • Cold bridging
121
Q

What can be the distinctive features of condensation?

A
  • Occurs between autumn to early spring
  • Starts on coldest internals surfaces (particularly corners), single glazed windows, wall to floor junctions, lintels and window reveals.
  • Occurs in rooms where lots of moisture is produced; kitchens, bathrooms, unheated rooms.
  • Occurs in areas where air movement is restricted; behind cupboards etc.
122
Q

What factors affect condensation and mould growth?

A
  • Moisture generation
  • Ventilation
  • Thermal insulation
  • Heating
  • Surface absorption
  • Temperature
123
Q

Where would you expect to see mould growth?

A
  • Cold corners
  • Behind furniture
  • Unheated rooms
  • Cold bridges
124
Q

How would you determine condensation risk?

A
  • Use of a psychometric chart, condensation will occur when RH reaches 100%.
  • This will allow you to plot the dew point based on the internal air temperature and relative humidity
125
Q

What are the remedial measures?

A
  • Fungicidal washes to remove mould
  • Provide adequate ventilation, reduce moisture generation, provide adequate heating and remove cold bridges
126
Q

What is a cold bridge?

A
  • A section of the construction which has a significantly higher heat transfer rate than surrounding materials, allowing heat to flow through the path created.
  • Bridging needs to be eliminated and rebuilt with materials of better insulating properties, or with an additional insulating element called a thermal break.
127
Q

What is interstitial condensation?

A
  • Condensation occurring within the building fabric, where the dew point is reached within a building element.
128
Q

What is an important design principle to avoid interstitial condensation?

A
  • A requirement to be designed so the temperature profile across the construction remains higher than the dew point.
  • Ensure the major vapour resistance is on the warm side of the major thermal resistance. I.e. below insulation in a warm deck roof.
129
Q

What equipment are you aware of when investigating damp?

A
  • Electrical Resistance Meter
  • Capacitance Meter
  • Speedy carbide meter
  • Infrared thermography
  • Electronic leak detection
130
Q

What does an electrical resistance meter tell you?

A
  • WME – Wood Moisture Equivalent i.e. the moisture content of timber
  • R/R (relative readings) for all other materials
  • Use WME equivalent tables for other materials as a guide.
131
Q

How does an electrical resistance meter work?

A
  • A current is run from one probe to another and measured to determine the resistance, the more moisture the less electrical resistance and therefore a higher reading
132
Q

What are the limitations of an electrical resistance meter?

A
  • Can only test non-conductive materials
  • Cannot be used to test hydroscopicity
  • Inaccurate readings will be given on foil backed plasterboard, where salts are present and building materials with a high carbon content (some types of breezeblock
133
Q

How would the use of pulverised fuel ash blocks affect your moisture readings?

A
  • PFA is carbonaceous, and therefore is highly conductive
134
Q

How do you calibrate an Electrical Resistance Meter?

A
  • Using a calibration block
  • Built in calibration check
135
Q

What basic rules would you follow when using moisture meters?

A
  • Make sure it is regularly calibrated
  • Test a wide area and range of materials, establish a control reading
  • Only compare readings, rather than assume high readings equate to damp
  • Remember that meters are primarily designed for timber
  • Do not rely solely on the readings, only use to provide additional evidence
  • Can be used to draw moisture contours, allowing you to profile the spread of moisture.
136
Q

What is the process of using a carbide meter?

A
  • A sample of material is collected, using drill sampling which must be slow so sample doesn’t dry due to friction.
  • A weighed sample of material is added and mixed with calcium carbide, any moisture will react and release acetylene gas.
  • This provides a reading, if less than 5% it is unlikely to be suffering from damp.
137
Q

What does a thermo-hygrometer tell you?

A
  • Can measure relative humidity and air temperature
  • Will tell you whether air in a room is unacceptably humid
  • Can be inserted into drilled holes to measure the equilibrium relative humidity and temperature, this will enable you to gauge whether the material is significantly damp
138
Q

What is electronic leak detection?

A
  • Introduces a low voltage electric current which pulses over the membrane, leaks in the roof can be pinpointed when a flow of electricity is detected.
139
Q

What are the two groups of wood rotting fungi?

A
  • White Rots – causes timber to become lighter in colour, without cross cracks. All white rots are wet rots.
  • Brown Rots – causes timber to become darker and crack across the grain
140
Q

What is the lifecycle of a wood rotting fungi?

A
  • Spores are present in the air which germinate if they land on a suitable substrate. i.e. damp timber
  • The germinating spores produce a thin thread like Hyphae which collectively form a mycelium.
  • The hyphae penetrate to timber, feed, and produce the fruiting body. This releases spores into the atmosphere.
141
Q

What features do you rely on for identification?

A
  • Structure and colour of the fruiting body and spores
  • Colour and appearance of mycelium and strands
  • Form of the decay, i.e materials affected
  • Other features: environment, type of timber, manifestation of the rot in the timber.
142
Q

What is the Latin name for the most common forms of wet rot?

A
  • Coniophora Puteana is a brown rot
  • Corniophora Marmorata – Brown Rot
  • Donkioporia Expansa – White Rot
  • Pleurotus Ostreatus – White Rot
143
Q

What guidance are you aware of for wet rot?

A
  • BRE Digest 345
144
Q

How would you identify wet rot?

A
  • Cracks follow the grain of the timber with light cross cracking
  • Rapid weight loss in timber
  • Olive green fruiting body, cream margin, knobbly surface – rarely found
  • Yellowish, thread like strands which become a darker brown with age.
145
Q

What does wet rot require to develop and grow?

A
  • Optimum growth between 50 and 60% moisture content
  • Unable to survive if the moisture content drops below 43%
  • No reaction to light, develops in dark areas
  • Only grows on timber
146
Q

What are the primary control measures for wet rot?

A
  • Locate and eliminate sources of moisture
  • Promote rapid drying of the structure
147
Q

What are the secondary control measures for wet rot?

A
  • Establish the size and significance of the outbreak
  • Remove rotted wood, consider the need to apply preservative in situ
  • Use preservative treated replacement timbers
  • Introduce support measures
148
Q

How would you specify the remediation of a Wet rot outbreak?

A
  • Eliminate sources of dampness; bridged/missing DPC, missing tiles, damaged rendering
  • Incorporate/encourage ventilation; insertion of sub floor vents, removal of floorboards.
  • Survey the affected area to determine the extent of the outbreak, limited to wetted areas only.
  • Remove all rotted wood, cutting away timber 300 to 450mm beyond the last indications of rot
  • Treat sound, damp timbers with preservative, or insertion of borate rods into wet timbers. Consideration should be given to the application of insecticides.
  • Install new preservative treated replacement timber, should be pressure impregnated with preservative
  • Additional measures such as bearing ends of timber on joist hangars, ensure adequate ventilation.
149
Q

What is the Latin name for the dry rot wood decay fungus?

A
  • Serpula Lacrymans
150
Q

How do you identify dry rot?

A
  • Softening of the timber, light in weight and crumbles
  • Shrinkage and distortion
  • Distinctive mushroom odour
  • Deep longitudinal and cross cracking to the timber
  • Dull brown colour
  • Develops out of sight, behind panelling, plaster or floor voids.
151
Q

How would you identify the dry rot fungus?

A
  • Strands: grey or white, 8-10mm, become brittle when dry
  • Mycelium: soft white cushions or silky growths, grey sheets in dryer places
  • Fruiting bodies: Fleshy/soft and shaped like pancakes. Spore bearing surface is rusty red, spores settles as a layer of rust coloured dust
152
Q

What type of timber does dry rot require?

A
  • Hardwood or softwood
  • Grows most rapidly on timber with a moisture content above 30% though not saturated >35%.
  • Cannot colonise wood which has a moisture content below 20%
  • Cannot survive in warm, dry above 20oC for extended periods
  • Light is required for growth of fruiting body.
153
Q

How can dry rot spread?

A
  • Can spread across timber and other cellulosic materials
  • Can grow within brick and plaster
  • Only sustained by strands from timber at the source of the outbreak
154
Q

What are the primary control measures for dry rot?

A
  • Locate and eliminate sources of moisture
  • Promote rapid drying of the structure
155
Q

What are the secondary measures for dry rot?

A
  • Determine the full extent of the outbreak
  • Remove rotted wood
  • Contain the fungus within the wall
  • Treat remaining sound timbers with preservative
  • Use preservative-treated replacement timbers
  • Introduce support measures
156
Q

How would you specify the remediation of a dry rot outbreak?

A
  • Eliminate sources of dampness; bridged/missing DPC, missing tiles, damaged rendering
  • Incorporate/encourage ventilation; insertion of sub floor vents, removal of floorboards.
  • Survey the affected area to determine the extent of the outbreak, where necessary remove skirtings and floorboards to inspect joists. Plaster removal is required where infected timber is in contact with wall surfaces.
  • Remove all rotted wood, cutting away timber 300 to 450mm beyond the last indications of rot
  • Application of fungicidal fluid for treating wall surfaces, after treatment all efflorescent salts should be brushed away prior to plastering.
  • Treat sound, damp timbers with preservative, or insertion of borate rods into wet timbers.
  • Install new preservative treated replacement timber, should be pressure impregnated with preservative
  • Additional measures such as bearing ends of timber on joist hangars, ensure adequate ventilation.
157
Q

What guidance are you aware of for dry rot?

A
  • BRE Digest 299
158
Q

What wood boring insects are you aware of?

A
  • Death Watch Beetle
  • Common Furniture Beetle
  • House Longhorn beetle
159
Q

How would you identify a wood boring insect?

A
  • Size of flight holes
  • Timber attacked
  • Size and shape of the insect
  • Pellet shape
  • Egg shape/size
  • Consistency of bore dust
160
Q

What are the risk factors for wood boring insects?

A
  • Type of timber
  • Moisture of timber
161
Q

What would you recommend to eliminate an insect infestation?

A
  • Confirm it is a current infestation and not historic
  • Dry timber is immune to attack, therefore the first action would be to eliminate the cause of dampness and promote rapid drying of the structure.
  • Where a serious and active outbreak is ongoing then the use of brush applied insecticides should be used.
  • Insecticides should contain at least 0.25% permethrin, in order to be classed as a curative treatment under the Biocidal Products Regulations when applied at 300mm/m2
162
Q

How would you identify a common furniture beetle infestation?

A
  • Timber attacked – sapwood of hardwoods and softwoods, plywood and wattling
  • Tunnelling in sapwood runs along the grain, contains bore dust, lemon shaped pellets contained within bore dust.
  • Exit holes are round, about 1.5 – 2mm diameter
163
Q

What is a life cycle of a common furniture beetle?

A
  • Life cycle of 3+ years
  • Adult – emerge May to August to mate… yay
  • Eggs – Laid in cracks, crevices, endgrain, old exit holes; white, lemon shaped.
  • Larva – Bores straight into the wood from egg, feed and grow for 3 or more years. Larvae reach 6mm in length
  • Pupa – Develop below surface of wood, pupal stage is 6-8 weeks prior to emergence.
164
Q

How would you identify a death-watch beetle infestation?

A
  • Timber attacked – Sapwood and heartwood of hardwoods, usually oak, which have partly decayed. Softwoods are rarely attacked.
  • Extensive tunnelling especially towards centre of large dimensioned timber, exit holes are round, 3mm in diameter
  • bore dust is bun shaped and contains pellets that are visible to the naked eye
  • Damage often more extensive than expected from external appearance.
165
Q

What is the Lifecycle of Death-watch beetle?

A
  • Life cycle of 4+ years
  • Adult - Emerge in March/June, eggs laid 10 days after mating
  • Eggs – Laid in cracks, crevices: White, lemon shaped
  • Larvae – crawl prior to boring into wood, feed and grow for 10+ years
  • Pupa – Develop below surface of wood in July – August
166
Q

How would you identify house longhorn beetle?

A
  • Attacks sapwood of seasoned hardwood
  • Very severe tunnelling in sapwood, can lead to structural collapse
  • Exit holes are oval (5mm x 9mm) and tunnels are flattened and full of sausage shaped pellets
167
Q

What is the lifecycle of house longhorn beetle?

A
  • 4+ years
  • Adult – Emerge July/September
  • Eggs – Laid in fan shaped pattern cracks in the wood, white spindle shaped, up to 200 laid
  • Larva – Feeds in sapwood for more than 4 years, causes extensive damage, reaches up to 30mm in length
  • Pupa – Takes place about 3 weeks prior to emergence
168
Q

You are inspecting a building and identify a number of cracks in an external wall, take me through your thought process?

A
  • Material of the wall and form of construction, wall ties
  • Local factors, trees etc
  • Note the location of any drainage in the vicinity
  • Any alterations previously undertaken
169
Q

What are the common causes of cracking?

A
  • Ground movement
  • Foundation failure
  • Thermal movement
  • Moisture movement
  • Decay of the building fabric
170
Q

What is the BRE guidance note on cracking?

A
  • BRE Digest 251
171
Q

What grades of cracking are given in BRE digest 251?

A
  • Grade 0 – Hairline cracks less than 0.1mm. no action required
  • Grade 1 – Fine cracks up to 1mm, treated using normal redecoration
  • Grade 2 – Cracks up to 5mm, doors & windows may require easing, some external repointing may be required to maintain weather tightness.
  • Grade 3 – Cracks between 5-15mm, weather tightness impaired, may require opening up to repair, repointing and small sections of masonry replaced.
  • Grade 4 – 15-25mm cracks, extensive damage which requires breaking out and replacing sections of walls. Services disrupted, walls leaning or bulging
  • Grade 5 – greater than 25mm, structural damage, danger of instability, beams lose bearing, walls require shoring, windows broken with distortion.
172
Q

What are the three classifications of cracks?

A
  • Classification one: Failures affect appearance only
  • Classification two: Fractures and cracks cause damage to the function of the wall i.e. weatherproofing and insulation.
  • Classification three: unacceptable risk of failure unless work is carried out.
173
Q

How would you investigate cracking in a building?

A
  • Record the damage
  • Ascertain the history of the site,
  • Record position, species and approximate age of nearby trees and shrubs
  • Record position and condition of nearby drains
  • Establish that cracking is consistent with foundation movement
  • Monitor
  • Investigate sub-soil by means of trial pits to reveal depth of foundations, presence of clay and roots below the foundations
174
Q

How would you monitor cracks?

A
  • Installation of tell-tales
  • Reading between fixed points with a Vernier gauge
175
Q

Rules regarding trees?

A
  • 1H Rule, limit the proximity to the maximum potential height of the tree.
176
Q

Are there any trees that may be of particular concern?

A
  • Willow
  • Poplar
  • Oak
177
Q

What is Subsidence?

A
  • Soil movement downwards, typically in shrinkable clay soils when their moisture content decreases.
178
Q

What is Heave?

A
  • Expansions of clay soils when wet, displacement is generally less than 150mm.
179
Q

What is settlement?

A
  • Downward movement of a foundation caused by an application of load occurring for a period of time immediately after construction.
180
Q

What are the remedies to ground heave?

A
  • Underpinning
181
Q

What types of underpinning are available?

A
  • Mass fill underpinning/hit and miss
  • Partial underpinning
  • Mini piling
  • Injection of cement grout
  • Stiffening beams
  • Pier and beam
  • Pile and beam
182
Q

Cracking between bay window and external wall?

A
  • Shallower foundations for a bay window causes differential movement
183
Q

How do you rectify subsidence to foundations?

A
  • Remove source of subsidence – e.g. remove tree, however assessment to be made regarding potential heave following. Atterberg tests can determine plasticity of clay soils.
  • Install root barrier to block any roots – needs to be installed at appropriate depth (greater than 2.0m)
  • Underpinning (as described before) – of up to 3.0m
184
Q

What is HACC?

A
  • High Alumina Cement Concrete
185
Q

When was HACC used?

A
  • Used extensively in the UK between the 1950s to early 1970, mainly in the manufacture of pre-cast, pre-stressed concrete beams.
186
Q

Why was it popular HACC?

A
  • Develops very high early strength, meaning shuttering could be struck within 24 hours of initial pouring.
187
Q

When were defects encountered with HACC?

A
  • A high profile collapse of a swimming pool roof in 1974.
188
Q

What is the issue with HACC?

A
  • The hydrated HAC undergoes a change in mineralogical composition with time, through a process of conversion. Conversion results in increased porosity and a loss of strength.
  • Makes the concrete more susceptible to carbonation, chloride attack and sulphate attack
189
Q

What can affect the rate of conversion?

A
  • Accelerated by higher temperatures
  • Moisture levels
  • Water/cement ratio
190
Q

What guidance relates to HACC?

A
  • The BRAC Guidance, identifies three stages of investigation: Identification, strength assessment and durability assessment.
  • Only applies to line cast X or I sections
191
Q

Are there any methods of visual identification for HACC?

A
  • Excessive deflection
  • Lateral bowing and cracking
  • Concrete can turn a chocolate brown colour
192
Q

What tests are available to confirm the presence of HACC?

A
  • Rapid chemical tests
  • Petrography
  • X-ray diffraction
193
Q

What is the process of the rapid chemical test?

A
  • Powdered concrete samples are taken
  • Mixed with sodium hydroxide, passed through a filter and mixed with hydrochloric acid, Oxine reagent and Ammonium Acetate.
  • If HAC is present the precipitate is a yellow colour
194
Q

What is shear cracking?

A
  • Forces pushing in opposing directions on the same material
195
Q

What are compression forces?

A
  • Forces acting in the same direction
196
Q

What is the BRE guidance note for concrete carbonation?

A
  • BRE Guidance Note 405
197
Q

How does carbonation occur?

A
  • Carbon Dioxide from the atmosphere penetrates the concrete and reduces the alkalinity, this reduces the passive protection around the reinforcement, especially where cover is poor.
  • This causes any reinforcement to corrode, expand and manifests as spalling concrete and exposed reinforcement.
198
Q

What testing can be undertaken to determine that carbonation has occurred?

A
  • Test with a phenolphthalein (alkaline solution), is an indicator solution which will turn pink if the concrete is not carbonated.
  • The test should be made on sections of broken off concrete, phenolphthalein should be mixed with ethanol and deionised water and sprayed onto the surface.
199
Q

How would you specify repairs to carbonated concrete?

A
  • Tap test any spalled areas, remove all spalled concrete to expose any corroded reinforcement.
  • Remove all corrosion, even to the rear faces of the rebar, and apply a zinc rich primer to prevent further corrosion.
  • Patch repair the areas with new cementitious material, with polymer reinforcement
200
Q

What is alkali Silica Reaction?

A
  • Caused when alkaline chemicals present in the cement react with silica contained within aggregates, a gel like substance forms, absorbing water and expanding.
  • This causes cracks in the concrete, this allows water into the concrete and corrodes the reinforcement
201
Q

What two forms of sulphate attack are you aware of?

A
  • Conventional or Ettringite form of sulphate attack
  • Thaumasite form of sulphate attack (TSA)
202
Q

What is the history of the problem?

A
  • Sulphate-bearing hardcore, derived from colliery spoil and other industrial by-products was included in the construction of properties between 1945 and 1970. Used as support for concrete floor slabs without the use of separating damp proof membrane.
203
Q

What is the mechanism of failure in conventional sulphate attack?

A
  • Sulphates and water react with the tri-calcium aluminate found in Portland cement which forms ettringite.
  • Ettringite is destructively expansive since it has a solid volume greater than its original constituents.
204
Q

What is required in order for deleterious amounts of ettringite to be produced?

A
  • Wet conditions
  • Significant concentration of water soluble sulphates
  • Concrete which contains a substantial content of calcium aluminate hydrates
205
Q

How would you recognise Sulphate attack?

A
  • Horizontal expansion of the floor slab and oversite concrete
  • When constrained at the abutments the concrete is typically lifted into a dome, this may achieve a deflection of several centimetres, accompanied with map pattern cracking
  • Displacement in masonry walls in worst cases, including disruption to the DPC
206
Q

How would you confirm sulphate attack as part of your inspection?

A
  • Expose the slab and record character and extent of any doming concrete
  • Further examination of the floor slab to confirm build up, construction and condition of any membranes
  • Sulphate tests can be undertaken, samples can be taken for petrographic analysis for absolute confirmation
207
Q

What are your remedial options for sulphate attack?

A
  • 4 options given in the BRE guidance
  • Precautionary periodic inspections – where only slight damage has been caused, no immediate requirement for remedial works
  • Removal and replacement of just the concrete floor slab and oversite concrete
  • Partial removal and replacement of hard-core and provision of new concrete slab
  • Complete removal and replacement of hard-core and provision of new concrete floor slab
208
Q

What are the likely causes of leaning chimneys on a property?

A
  • Potential sulphate attack, sulphates from flue gases allows the formation of hydroscopic salts within the mortar of unlined chimneys.
  • The crystallisation of salts as moisture evaporates on the slow drying side leads to the widening of joints.
  • On the quick drying side, the prevailing wind and rain will deteriorate the joints.
209
Q

How would you determine whether the lean was excessive?

A
  • The BRE Guide states a lean of more than 1mm in 100mm is unsafe, this may be too cautious with historic buildings
  • The middle third rule
210
Q

What is the middle third rule?

A
  • Structural engineering principal, i.e. where the shaft wall is a half brick thick, a lean of 35mm could be tolerated.
  • Based on the restriction that the eccentricity should be within the middle third of the width of a wall.
211
Q

What BRE Digest relates to chloride attack?

A
  • BRE Digest 444
212
Q

When were calcium chloride additives used?

A
  • An accelerator used in the 1950’s and 60’s.
  • Banned in 1977
213
Q

What is chloride attack?

A
  • Water bearing chloride ions are deposited on the concrete surface, allowing the ions to penetrate the concrete
  • When the chloride reaches the steel it reacts with the hydrogen ions in the pore water to create acids which cause pitting corrosion
214
Q

How would chloride be present in concrete?

A
  • Use of sea washed aggregates
  • De-icing salts
  • Sea salt ingress
  • Deliberate use of sea water in the mix
  • Addition of calcium chloride accelerators
215
Q

What are the “safe” levels of chloride concentration?

A
  • 0.4% chloride by mass represents a low corrosion risk
  • 0.4 – 1% represents a medium risk
  • Above 1% is considered a high risk
216
Q

How can chloride attack be remedied?

A
  • Repair strategy must include the breakout of chloride contaminated concrete in contact with the reinforcement
  • Use of cathodic protection or electrochemical chloride extraction of the cover concrete.
217
Q

What is electrochemical chloride extraction?

A
  • Where a high current (1A/m2 of concrete surface) is passed through the material to pull chlorides away from the steel.
  • Takes 6 to 8 weeks, only works where the chlorides have not penetrated beyond the first level of reinforcing steel.
218
Q

How does Regent Street Disease occur?

A
  • In the early 20th century it was common practice to construct load-bearing frames of steel, clad on the external faces with stone brick or terracotta.
  • The cladding would be notched around the frame and infilled with low grade mortar.
  • Water and oxygen makes its way into the structure , corrodes the surface of the frame and expands. This causes cracking to the surface materials.
219
Q

What are the remedial options for Regent Street Disease?

A
  • Cathodic Protection
  • Removal of stonework, blasting or needle gunning exposed metalwork, application of a corrosion inhibitor and re-instatement of stonework.
220
Q

What is cathodic protection?

A
  • The passage of a DC current into the metalwork to reverse the direction of electrical currents associated with corrosion.
  • It does not make good corrosion, but suppresses the continuation of the process.
221
Q

What are the different types of flat roof construction?

A
  • Cold Roof
  • Warm Roof
  • Metal Roofs
  • Green roof
222
Q

What are the main types of roof covering that could be specified for a flat roof?

A
  • Reinforced bitumen membranes – 2 or more layers bonded with hot bitumen (single layer systems exist also)
  • Polymetric single-ply – laid and can be fully fastened, fully adhered to, or loose laid and ballasted
  • Mastic asphalt – graded limestone aggregate bound together with asphaltic cement (bitumen). Heated to 120 degrees & applied with wooden float
  • Liquid roof systems – monolithic, fully bonded, liquid-based coating with rubberised finish
  • Profiled sheets:
    o Lead, zinc, copper and steel
223
Q

What are common defects associated with flat roofs and what are the remedies?

A
  • Crazing - Surface crazing caused by lack of protection from UV exposure. No treatment is required if in small localised patches but should be monitored.
  • Ponding - If the gradient is not sufficient and there are dips in the roof finish, it can lead to pools of water. It can lead to water ingress if there is a gap in the roof finish.
  • Thermal Movement
  • Cracks and splits can occur when there is thermal movement between the substrate and membrane. Usually requires localised repair to the area around the crack.
  • Blistering - Caused when water vapour beneath the roof finish increases. The source of moisture should be traced and the blister opened and allowed to dry before patch repairing.
  • Flashing and Falls around openings- Defective lead from deterioration or poor workmanship around openings causing water ingress. Depending on the issue with the lead, there are different repairs.
  • People - Punctures caused by people from impact damage.
  • Cracks and tears along the line of joists - Caused by thermal movement or saturation of insulation or sagging decking. Repaired by cutting felt back and allowing it to dry before patching over.”
224
Q

What is the minimum gradient for a flat roof to shed water effectively?

A
  • Minimum grade of 1:40
225
Q

What can cause ponding on a flat roof?

A
  • Tapered insulation or roof deck not laid to correct falls (timber furrings used to set roof deck falls)
  • Deflection of timber roof deck – through reduction in structural integrity of structural timbers – rot / insect infestation
  • Blocked RWGs
  • Subsidence / heave
226
Q

What the positives and negatives of cold and warm flat roofs?

A
  • Cold roofs:
    o As the roof void is cold there can be issued with interstitial condensation as warm air from inside the building enters the unheated roof space allowing condensation to form on the timber roof joists and deck - this make them susceptible to rot and therefore structural failure eventually. Require vented 50mm gap between bottom of roof deck and top of insulation to try and prevent.
    o More complicated to construct - insulation between the joists rather than just on top of roof.
    o Greater chance of thermal bridging - ceiling joists are not insulated.
    o Benefit: as insulation is between joists there is no change to roof height - this could affect roof height relative to the parapet walls - may need to extent them etc
  • Warm roofs:
    o Easier to install.
    o Can be retrofitted.
    o Less chance of thermal bridging.
    o Drawback - external roof height will be raised.
227
Q

What are the defects associated with GRP rooflights?

A
  • Loss of transparency, embrittlement, etc. caused by ultraviolet light breaking down polymers in the rooflight plastic
  • Incorrect installation – 2 lines of sealant should be installed to each end (recommended by manufacturer)
  • Embrittlement of foam fillers by UV degradation
228
Q

What is the life expectancy of mastic asphalt?

A
  • Up to 60 years when property maintained
229
Q

What is asphalt?

A
  • A blend of asphaltic cement with graded fine aggregates, forms a voidless mass once cooled.
230
Q

When was asphalt roofing most popular?

A
  • During the 1950s and 60s on uninsulated decks.
  • When the use of insulation increased, the lifespan of asphalt is shortened, due to not being able to dissipate heat into the structure.
231
Q

What are the typical defects of asphalt roofing?

A
  • Blistering
  • Splits/cracking/crazing
  • Ponding
232
Q

What causes blistering?

A
  • Moisture trapped behind the asphalt vaporises and forms a blister, repeated cycles result in perforation of a blister and water ingress
233
Q

What causes cracking?

A
  • Deck deflection
  • Thermal movement
234
Q

What is the guidance for asphalt roofing?

A
  • Mastic asphalt council technical guidance
  • BS 8218 – 1998 – Code of practice for mastic asphalt roofing
235
Q

What is the typical build up?

A
  • Joists
  • Firring
  • Deck
  • VCL
  • Insulation
  • Separating membrane between insulation and asphalt
  • 20mm two coat mastic asphalt
  • Solar reflective treatment
236
Q

What are the defects related to felt roofing?

A
  • blistering
  • ponding
  • poor workmanship
  • damage by foot traffic
  • moisture retention
237
Q

What is the typical lifespan of a felt roof?

A
  • 15-20 years
238
Q

What measures can you take to check whether water ingress has occurred in a flat roof?

A
  • Internal inspection
  • Electronic leak detection
  • Core samples
  • Moisture mapping
239
Q

How is lead manufactured?

A
  • Rolled lead sheet – BS EN 12588: 2006
  • Sand cast
  • Machine casting
240
Q

What are common defects you may encounter in a pitched roof?

A
  • Nail sickness
  • Slipped/loose slates
  • Loose hip and ridge tiles
  • Defective stepped flashings
  • Rotting soffits and fascia
  • Roof spread
  • Dishing or sagging
241
Q

What is nail sickness?

A
  • Slates slipping due to failure of poor quality galvanised or iron nails.
  • Caused by the corrosion of the fixings due to exposure.
242
Q

What would you recommend to address a roof suffering from nail sickness?

A
  • Isolated repairs in minor incidents, refixing using aluminium or copper fixings
  • If 15% of the roof is suffering, consideration should be given to replacing all of the slates.
243
Q

What are the ventilation requirements in a pitched roof?

A
  • With a pitch greater than 15° but less than 70° with insulation at ceiling level requires a 10mm continuous air path at the eaves.
  • Greater than 15° pitch with insulation at rafter level, requires 25mm at the eaves and 5mm at the ridge, a minimum 50mm air path should be maintained between the top of the insulation and the underside of the roof decking.
244
Q

What might cause sagging of a pitched roof?

A
  • Loss of structural support, indicate issues with purlins or rafter
  • Installation of concrete tiles, where slates or clay tiles may have been installed originally.
  • Poorly executed loft conversion
  • Beetle infestation
  • Roof spread
245
Q

How would you prevent roof spread?

A
  • Installation of struts or ties, tying the rafters back to the wall plate or joists with a dragon ties.
246
Q

What does head lap mean?

A
  • When the head of the slate is overlapped by the slate two courses above it.
  • Amount of head lap is determined by the pitch of the roof, the lower the pitch the greater the headlap.
247
Q

What are the common defects in lead?

A
  • Cracking and splitting due to the thermal expansion and contraction.
  • Deterioration where interstitial condensation can from on the underside when laid on a warm roof.
248
Q

What is cut edge corrosion? What causes it? How would you remedy it?

A
  • Caused by cutting each profiled metal roof sheet to length, causes micro cracking of the protective corrosion which lead to
  • corrosion of underlying metal in presence of moisture.
  • Can be caused by moisture being trapped in lap joints (held by capillary pressure) – breaks down protective coating.
  • Dirt traps can occur at edge of sheet (if levels off) which can lead to further dirt and moisture build up = deterioration of
  • protective coating + corrosion.
  • Issue treated by cleaning the affected area (chemical cleaner/blast cleaning etc) then applying silicone based paint system
  • over priming layer according to manufacturer’s instructions. E.g Girosil Edge RC-E.
249
Q

What is Japanese Knotweed?

A
  • A bamboo like perennial plant, spreads through underground rhizomes. Introduced into the UK in the mid-19th century but is now deemed an invasive species.
250
Q

Why is JK an issue?

A
  • Grows approximately 20cm a day
  • Hard and expensive to eliminate and dispose of.
  • Effects the ability to secure mortgages and insurance on properties with knotweed.
  • Defined as controlled waste under the Environmental Protection Act 1990
251
Q

Under what law is JK controlled?

A
  • Wildlife and Countryside Act 1981
252
Q

What types of defects can it cause?

A
  • Blocking drains and other buried services
  • Disruption of patios and other hardstandings
  • Can undermine boundary and retaining walls
  • Can overwhelm lightweight or poorly founded outbuildings
  • Ruin well planned gardens
253
Q

How would you identify JK?

A

Summer
- Red/purple shoots/spears
- Small white flowers
- Lush green leaves, shield shaped, with a flat base.
- Stems are hollow, are green with distinctive purple speckles.
- Zig zag stems, with alternating leaves

Winter
- Brown stems remaining from the summer growth
- Hollow like bamboo

254
Q

How can JK be treated/removed?

A
  • Excavation of the plant and its roots – volume is typically 3m below ground and 7m horizontally from the above ground growth. Includes the segregation of Rhizomes and Crowns.
  • On site burial and/or encapsulation – must be covered by more than 5m and a root barrier membrane installed to prevent growth, or the root barrier can be used to encapsulate the knotweed.
  • Chemical Control – The most realistic option in the residential context, multiple treatments with glyphosate over a long period to bring the knotweed under control.
255
Q

What are the Risk categories for Japanese Knotweed stated in the guidance note?

A
  • Category 4 – Knotweed is within 7 meters of a habitable space, either within the boundary or in a neighbouring property/area AND/OR, Knotweed is causing serious damage to outbuildings, structures, drains etc. - further investigations required by a qualified person.
  • Category 3 – Knotweed present within the boundaries, but more than 7 meters from a habitable space – further investigations required by a qualified person.
  • Category 2 – Knotweed not seen within the boundary, but was seen on neighbouring property or land within 7 meters of the boundary. But more than 7 meters away from habitable spaces.
  • Category 1 – Knotweed not seen on the property, can be seen on a neighbouring property or land where it was more than 7 meters from the boundary.
256
Q

What do mortgage lenders require in order to allow lending on a property with knotweed?

A
  • Evidence of an initial treatment
  • A commitment to fund, in advance, a three or four year treatment programme effective against Japanese knotweed.
257
Q

Any famous case law for JK?

A
  • Network Rail Infrastructure v Williams & Waistell – Network rail lost as Japanese knotweed spread from NR’s land, caused a nuisance and interfered with the quiet enjoyment of the claimant’s properties.
258
Q

What is Giant Hogweed?

A
  • A large umbellifer (member of the cow parsley family)
  • Up to 3m tall with large flowers up to 80cm in diameter, leaves of 1m or more in size
259
Q

What is the problem with Giant Hogweed?

A
  • Produces phytotoxic sap which contains photosensitizing furanocoumarins.
  • When contact is made with human skin and combined with UV radiation causes the skin to burn, skin can remain sensitive indefinitely.

APC - JC (30 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions