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APC > Building Pathology > Flashcards

Building Pathology Flashcards

1
Q

What are common defects of concrete frame buildings?

A
  • Carbonation
  • Sulphate attach
  • High Chloride Content
  • Freeze thaw
  • Alkali - Aggregate Reactivity
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2
Q

What are common defects of steel frame buildings?

A
  • Corrosion
  • Cut edge corrosion
  • Steel rivet corrosion
  • Fatigue cracking
  • Distortion
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3
Q

What different methods for identifying defects are there?

A
  • Leak investigations
  • Protimeter
  • Phenaphaline solution
  • ## Core sampling
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4
Q

What are the common defects of timber frame buildings?

A

Engineered timber
- delamination
- infestation
- rot

Traditional timber
- rot
- infestation

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5
Q

What is RAAC stand for?

A

Reinforced autoclaved aerated concrete?

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6
Q

What is RAAC and why was it used?

A

It is made by mixing the concrete mixture with an aerating agent to create a lightweight aero like composition and curing it in an autoclave.

  • used due to its lightweight
  • good insulation properties
  • fire resistance
  • relatviely cheap
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7
Q

When was RAAC widely used?

A

1950s - 1990s

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8
Q

What are the risks or RAAC?

A
  • Mainly old RAAC
  • Usually due to pooor installation - such as cutting or pnetrating
  • Performance Defects - inc. corrosion of reinfacoement, cracking and spalling, overloading
  • Manufacturing defects - insufficient anchorage or poor rebar cover
  • Construction defects - short bearing lengths, post manufacture cutting of panels
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9
Q

What are the remediation options for RAAC?

A
  1. Leave and monitor
  2. Prop
  3. Increase or improve end bearing support
  4. Full span support
  5. Replace
  6. Demolish building
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10
Q

How do you identify RAAC?

A
  • typically 600mm width panels
  • V-shaped grooves at regular spaced intervals
  • Light grey in colour
  • Note of any of the following suppliers: Siporex, Durox, Celcon, Hebel and Ytong
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11
Q

What is the form of construction of a the residential mews property in south kensington?

A
  • Load bearing solid brickwork walls
  • Suspended timber flooring
  • mansard roof with slate tiles
  • brick footing foundations
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12
Q

What is asphalt?

A

Asphalt is a semi solid petroleum. Formed through a mixture of aggregates and bitumen.

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13
Q

What is the timber moisture content to be prone to rot?

A

Wet rot is 50% and above
Dry rot from 20%

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14
Q

How to identify dry rot?

A
  • Deep cracks in timber grain
  • brittle/ crumbly timber
  • orange/brown spores
    -grey strands
  • fruiting bodies
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15
Q

How to identify wet rot?

A
  • softened or spongy timber
  • black brown fungal growths
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16
Q

What is the latin name for dry rot?

A

Serpula Lacrymans

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17
Q

What is the latin name for wet rot?

A

Coniophora Puteana

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18
Q

What is Nickel Sulphide Inclusions?

A

NiS is a small crystal like impurities in glass. During the glass tempering process where the temperatures are raised it activities the NIS crystal. During its life it can then subsequently cause the glass to shatter due to changes in temperature in the surrounding atmosphere.

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19
Q

How to reduce presence of NiS in manufacture?

A

Heat soaking can be done to tempered glass (c.287’C) which should cause NiS to expand and shatter glass before it has a chance to be installed.

This is an expensive process however.

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20
Q

How to identify/ analyse for presence of NiS?

A

Post shatter, the glass break point can be reviewed under an electron microsope for the small inclusion.

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21
Q

Why is NiS a problem?

A
  • H&S concern
  • Costly to replace
  • Often can’t get a warranty against NiS failure
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22
Q

What is a standing seam roof/cladding panel?

A

Each metal pan has a fastening that means it can be attached to another panel without the need for exposed fixings

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23
Q

What is cut-edge corrosion?

A

The steel sheets are protected in a anti corrosion coating, however where they are cut to size. this area can often be exposed to the elements and lead to corrosion.

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24
Q

How do you remedy cut edge corrosion?

A

Depending on severity:
- Replace panel
- Remove corrosion, apply an anti-corrosion primer, apply a reinforced tape over the cut edge and coat over that with a waterproof coating.

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25
Q

What budget cost dis you allocate for the remedials of the cut edge corrosion at the office in monument?

A
  • £30 per linear metre. = circa £2800
  • Prof fees on top
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26
Q

What is concrete carbonation?

A

Concrete carbonation is when CO2 in the atmosphere reacts with teh concrete, reducing its alkalinity. Once alkalinity reaches 11ph the passivating layer around the reinforcement can be breached, allowing corrosion of the steels.

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27
Q

What is concretes natural pH?

A

12.6

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28
Q

What factors determine rate of carbonation?

A
  • High cement to water ratio slows the rate of carbonation.
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29
Q

What is the recommended concrete cover around reinfocement?

A

It depends on a number of different factors like use/location and exposure factors. This is all set out in BS8110.

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30
Q

Why is carbonation prone in buildings built in 1950s-60s?

A

As carbonaton has had chance to set in, and concrete cover over reinforcements wasnt as regulated and has been found to be as low as 10mm.

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31
Q

How do you measure concrete cover?

A

A Cover meter, which is a non intrusive device that sends electromagnetic pulses through the concrete.

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32
Q

How do you measure the depth of carbonation?

A
  • using a phenophalein solution.
  • apply to a core sample
  • Purple stain means no carbonation
  • clear means carbonation
  • need to leave for 24 hrs
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33
Q

What carbonation preventative methods are there?

A

Anti-carbonation coatings to concrete, which prevent the ingress of CO2. This solution should be applied every 10 years.

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34
Q

What remedial solution is there for carbonated concrete?

A
  • Remove loose and damaged concrete, expose corroded steel.
  • Descalea corrosion and apply ani corrosion coating to steel
  • Replace concrete, aim for a higher cement to water ratio.
  • Apply anti-carbonation coating.
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35
Q

What is a high chloride content?

A

High Chloride content can cause coorosion of reinforcments. It can be caused by external factors such as icing salts/seawater, or can be found in some concrete admixtures used for accelorating curing.

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36
Q

Whats the testing procedure for high cloride content?

A

Crush a small sample and extract chrloride with a chamical solution.

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37
Q

What is the acceptable levels of chlorides?

A

less than 0.4% is low risk
between 0.4 and 1% is medium risk
above 1% high risk

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38
Q

What is Sulphate Attack?

A

Sulphate ions attacks componene of concrete paste and causing the concrete to crack and detiorate. Sulpahte can be found from external sources like: groundwater, seawater or wastewater, or, internally through some gypsum agregates or some admixtures.

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39
Q

How do you identify sulphate attack?

A

The surface of the concrete will have sodium sulphate deposits.

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40
Q

What is Alkali Aggregate Reactivity?

A

Two types Alkali Silica reactivity ASR, and, Alkal-carbon reacitivtiy (ACR). ASR is more common and causes an expansive reaction by forming a gel that absorbs moisture.

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41
Q

How do you identify ASR?

A

Produces a mapped or crazed cracking style.

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42
Q

How to reduce liklihood of ASR?

A
  • Use low alkali portland cements
  • Use certain pozzolins that reduce alkalinity.
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43
Q

What remedial solutions are there for ASR?

A

ASR doesnt typically damage a structure enough to be out of service, often only surface cracks. However this can allow thnigs in such as freeze thaw etc.

Proactive solutions such as the use of low alkaline portland cements or pozzolins can reduce impact/liklihood.

BRE Digest 330

44
Q

What is regent Street disease?

A

Corrosion of the steel frames within masonry or cement clad buildings. It is due to the fact that no space was left between the cladding material and steel which meant that once the cladding material inevitably absorbed water and caused the steel to expand it cracks the coating/cladding.

45
Q

What remedial solutions are there for regents street disease?

A
  • remove stonework to expose steels and remove rust before applying a anti corrosion coating
  • Cathodic protection for preventing further/future coorosion
46
Q

What is HAC?

A

High Alumina Cement assisted in the speed of curing for concrete. used often in maratime siutations. however can react badly to water and chemicals causing concrete to become friable.

47
Q

How do you ID HAC?

A

The concrete becomes friable and can often turn a chocolate brown colour and it is a particular issue in structural members such as roofs in warm moist environments.

48
Q

What is the remedy for HAC?

A

For HAC there is no known cure or treatment. Any patch repairs and external protective treatment can only delay the inevitable decay. Where HAC is identified its strength should be assessed and monitored? A document known as BRAC (Building Regulation Advisory Council) identify 3 stages of investigation: Identification, strength assessment and durability assessment.

49
Q

What are common defects of a flat roof?

A
  • Crazing
  • ponding
  • thermal movement
  • blistering
  • poor flashing details
  • inadequate falls
  • cracks and tears
50
Q

What should consider when diciding to repair or replace a flat roof?

A
  • Age
  • Condition
  • Extent of Defect
  • Cost
  • Use
  • Life Cycle Costing
  • Disruption associated with repair and replacement
  • Clients intentions for the building
51
Q

What is a Speedy Carbide Meter?

A

A speedy carbide meter is a device to measure moisture in masonry through slow drilling masonry and putting dust into a sealed container with a known measurement of calcium carbide. It releases a gas in proportion to the amount of moisture present

52
Q

How would you identify rising damp? What are the causes? How would you remedy it?

A

RISING DAMP - 1m high tide mark, peeling and blistering of wall finishes, musty smell, rotting of timber, hyproscopic salts. Use of Speedy carbide meter to measure moisture. The readings with moisture meter result in high surface readings, often with slight decline, finishing with a sudden cut-off
CAUSES – No damp proof course, DPC bridged by pointing, render, soil, paving, mortar droppings, affects both solid and suspended floors.
REMEDY – Remedy DPC problems, remove bridging of DPC, chemical injected DPC

53
Q

How would you identify penetration damp? What are the causes? How would you remedy it?

A

PENETRATION DAMP – dependant upon the levels of exposure of the building and often penetration only occurs in certain areas. The first sign of damp penetration is often the appearance of damp patches on walls, ceilings or floors. These tend to grow or darken after periods of heavy or prolonged rain.
CAUSES – Rain driving through exposed masonry walls that have insufficient thickness, problems with cavity trays, cracked or detached rendering, defects to window cills, blocked cavity ties
REMEDY – Repointing of defective mortar joints, apply masonry water repellent, make good defective joint details, inspect cavity tray and cavity ties for blockages, inspect areas of roofs such as chimneys, parapets and thresholds

54
Q

What is a cold bridge?

A

A cold bridge is created when materials that are poor thermal insulators come into contact, allowing heat to flow through the path created, although nearby layers of material separated by airspace allow little heat transfer. Insulation around a bridge is of little help in preventing heat loss or gain due to thermal bridging; the bridging has to be eliminated, rebuilt with a reduced cross-section or with materials that have better insulating properties, or with an additional insulating component, called a thermal break

55
Q

What other sorts of cracks would you expect to see on a brick building and what might have caused them?

A

Subsidence – A movement down in the ground level. In clay soil, the growth of large trees which remove water from the ground can cause this. This leads can lead to vertical cracking if in the centre of the building or diagonal cracking if at the corner of the property. The cracks will be larger at the top and thinner at the bottom.

Heave – A movement upwards in the ground level. In clay soil the removal of a tree will lead to an increase in the moisture content of the soil which will cause the soil to swell. This leads to vertical cracking if in the centre of the building or diagonal cracking if at the corner of the property. The cracks will be larger at the bottom and thinner at the top.

Settlement – A movement down due to an increased load. Buildings will settle when first constructed or if there is a change in the load as the new load settles to the bearing capacity of the soil.

Differential Settlement – If two sections of a building are constructed off different foundations or the ground is made up of different soil types or strata then one may settle more than another causing cracking between the two sections of the building. Most common with extensions.

Thermal movement – Either expansion or shrinkage of the masonry, is often characterised by vertical cracks with a relatively constant width if appropriate expansion joints are not present

Lintel failure – Lintel failure allows a triangular section of brickwork above the window to drop down creating a triangular crack from the corner of the window toward the centre.

Corroded Steel lintel – Where a steel lintel has been used above an opening and the edge is exposed or close to the surface this can corrode over time and expand causing cracking.

Cavity wall tie failure – corrosion of large steel fishtail ties will lead to cracking every 4 or 5 courses as the steel expands.

Internal alterations – Where a wall has been removed and a steel beam put in its place without consideration to the increased load acting upon wall the beam is bearing upon. Or where a staircase has been moved without thought to the lateral restraint of the flank wall.

56
Q

What cracks should cause a concern?

A

I would refer to BRE Digest 251

Cat 0-2 tend tobe either hairline or easily covered/fixed
3-4 more extensive/severe 5-25mm
Cat 5 is structural damage 25mm+

57
Q

What types of soil are more susceptible to heave/subsidence?

A

Cohesive soils suchas clay.

58
Q

What are the remedial measures to dry/wet rot?

A

Locate and eliminate the sources of moisture, promote rapid drying, remove rotted wood (450mm beyond last indications of rot and burn), surface application of fungicidal fluid, introduce support measures if required.

59
Q

Name some common insects that are known to attack timber?

A

Common furniture beetle
Deathwatch beetle
House longhorn beetle
Wood boring weevil

60
Q

Conditions prefered by woodworms?

A
  • softwood
  • humid and good moisture content in timber
61
Q

How to identify woodworms/infestations?

A
  • bore holes
  • Frass (exit dust and beetle shit)
62
Q

How to treat infestations?

A
  1. Identify the species - as will slightly alter the type of remedial required
  2. Remove affected wood - if severely damaged
  3. Apply insecticide - can vary from sprays, liqiuds injections and fumigants.
63
Q

What are three main types of Asbestos?

A

Crysotile (white) - roof coatings, cement asbestos
Amosite (brown) - insulation and fire protection
Crocidolite (blue) - spray coatings

Three other types
- Anthophyllite
- Tremolite
- Actinolite

64
Q

What is cavity wall tie failure?

A

Corrosion of the cavity wall ties that lesd to horizontal cracking in bricwork.

Identify it using a boroscope. isolate remove wall ties and replace with stainless steel ties.

65
Q

Name some defects in 1960s/1970s commercial buildings.

A

Asbestos, carbonation, HAC, Chloride attack.

66
Q

What are some common defects in victorian buildings?

A
  • If it is a cavity wall - Wrought iron cavity wall tie failure
  • Poor tying in of cavity flank walls
  • Rogue bricks - allowing water penetration (isolated wet spots)
  • Rot to windows and timber structure
  • Book end effect (removal of lateral supports ina terrace)
  • Poor modern alterations that remove ventilation
  • ## Change of loading due to roof structure
67
Q

Where might you find information or guidance on the rate of carbonation in concrete?

A

BRE Digest 444
BRE Digest 405

68
Q

What are the potential remedial solutions available for carbonation and/or a high chloride content?

A

Both cause corrosion to the steel reinforcement due to the break down of the steel passsivating layer.

Preserving or restoring passivity
- increase concrete cover
- replace carbonated or chlorinated concrete
- electrochemical realkilisation
- electrochemical chloride extraction

Increasing resistivity
- limiting moisture ingress by coatings/ surface treatments

Cathodic control
- Limited O2 ingerss by saturation or surface coatings

Cathodic Protection
- Galvanic or impressed current protection

Control of anodic areas
- coating reinforcements
- application of chmical corrosion inhibitors

69
Q

What guidance can you review in regards to ASR

A

BRE Digset 330

70
Q

What does Sulphate attach detiorate in concrete?

A

The cemet paste that bonds it.

71
Q

When was HAC commonly/extensively used?

A

1960s and 1970s

72
Q

Can you name some common defects in masonary/brickwork?

A
  • Wall tie corrosion
  • Calcium Silicate Brickwork
  • Fletton Brickwork (London Bricks)
  • Brick slips
  • Lack of movement joints
  • Frost attack
  • Solluable solt crystallisation
73
Q

What is Calcium Silicate brickwork and what are the issues?

A
  • Formed with aggregate, lime and water in an autoclave. Often used in the inner leaf of cavity walls.
  • High drying shrinkage rates
  • poor resistance to frost when contaminated by chloride (sea water) so not suitable for coastal areas
  • Unrestrained thermal expansion
74
Q

What remedials are there for Calcium silicate brickwork?

A
  • Adquate movement joints
  • Sulphate resistant mortars
  • Apprprioately selected mortar mixes to allow flexibility
75
Q

What is fletton brickwork and what are the issues?

A
  • Common in 1960s brick buildings
  • Red/pink colour
    Issues:
  • high sulphate content
  • when wet the sulphate reacts with the portland cement mortar. The mortar expands anc causes damage to the brick.
    Issues tend to arise in exposed areas: chimneys and parapets etc
76
Q

What are the remedial solutions for Fletton brickwork?

A

None once the sulphate attack has occured.
- Rendering over often causes more issues.

77
Q

What is the best practice requirement for movement joints in brickwork?

A
  • every 12m in new brickwork
  • Calcium silicate brickwork should have movement joints every 7.5m
78
Q

What is soluble salt crystallisation and why is it an issue and remedials?

A

Efflorescence from the salts in bricks or atmosphere deposited when moisture in the brick evaporates
- Can cause delamination of the brickwork faces.

Remedials
- Remove source of water
- replace brickwork if in poor condition.

79
Q

Name some forms of ground movement?

A
  • Subsidence
  • Heave
  • Settlement
80
Q

Summarise the signs, cause and remedials of subsidence?

A
  • Downwards movement of the ground caused by changes in ground i.e. large trees, broken drains.
  • Identified by diagonal cracking that is wider at the top.

Remedials - removing source of problem.
Underpinning methods

81
Q

Summarise the signs, cause and remedials of heave?

A

Upwards ground movement caused by expansion.
- felling of trees near the building
- Often in clay soils

remedials
- avoid removing trees, pollarding is a good alternative and should be done before hand if tree needs to be removed
-

82
Q

What is the lifecycle of Dry Rot?

A
  1. Spores - fungus present in the air
  2. Hyphae - start to grow as fine white strands on damp wood.
  3. Mycelium - Forms a cotton wool like substance, spreading over the building looking for more cellulose.
  4. Fruiting Body - Mushroom like fleshy pancake in a red/orange/brown colour.
83
Q

What is the main difference between dry and wet rot?

A

There is only one dry rot fungi, known as Serpula Lecrymans, whereas there are many different types of wet rot.

Dry rot is also around the 20% moisture content, compared to plus 50% for wet rot.

84
Q

What BRE Digest refers to Infestations?

A

BRE Digest 327
BRE Digest 307

85
Q

What remedial solutions are available for wood boring insects?

A

Identify whether it still is an active infestation!

Insecticidal treatments
- Surface treatments - only suitable for certain time periods when insects are on the surface.
- Injection treatments
- Fumigation treatments

85
Q

What is the lifecycle of a typical wood boring insect?

A
  1. Egg (10 days)
  2. Larva (1-5 yrs)
  3. Pupa (6 wks)
  4. Adult (Two-3 weeks)
86
Q

What are the treatments for each insect infestations type?

A

Common furniture bettle = Brush or spray of liquid insecticide
Deathwatch = Dry out the timbers then apply insecticide

87
Q

Can you name me some types of wood boring insect?

A
  • Common Furniture bettle
  • House longhorn beetle
  • Deathwatch bettle
  • Lyctus powderpost bettle
  • Weevil
88
Q

Types of cladding insultation and wheter they are combusitble?

A

Foamglass - non combustable
Polyisocyanurate (PIR) - Flaming can take place
Polyurethane (PUR) - Flaming can take place
Polystyrene (EPS) - Shitting flammable AF
Mineral Fibre - Non-combustible
Phenolic foam - generally non combustible

89
Q

What fire test is performed on ACM panels?

A

BRE will do a fire test in line with BS EN ISO 1716:2018

90
Q

What British standards are there for FIre performance on cladding systems?

A

BS 8414

91
Q

When was the market in London built?

A

It was originally constructed in 1920s however has had subsequent extensions and alterations since.

92
Q

In addition to the corroded steel lintel what other defects did you note?

A
  • Minor cracking
  • Defective/ blown double glazing units
  • Wants for decoration
  • Damaged/cracked georgian wired glazing to the roof lights
93
Q

What are some typical defects of 1920 steel frame buildings?

A
  • Regents street disease
94
Q

Tell me about the common furniture beetle?

A
  • The woodworm most responsuble for timber damage in the UK
  • Emergence between May-Sep
  • Found in softwoods, EU Hardwood and plywood
  • Timber with greater than 12% moisture
95
Q

How should you stop Japenese knotweed?

A
  • Apply herbicide - this may take several applications over a few years
  • Buried with a root membrane - 5m deep or 2m with membrane
  • Dug and sent to a knotweed site - 3m vertically and 7m radius around emerging growth

Look for a contactor with the following accreditations:
- Amenity forum membership
- BASIS Professional Register
- BASIS amenity training register
- basis nominated store keeper

96
Q

Where would you typically find japenese knotweed?

A
  • Railways
  • made up ground
  • common fly tip areas such as industrial sites
97
Q

What is the technical word for a japenese knotweed root, that are the source of growth?

A

Risomes

98
Q

What other invasive species are you aware of?

A
  • Giant Hogweed (can cause serious burns)
  • Himalayan balsam (easy spread)
99
Q

What causes asphalt to bubble?

A

When moisture infiltrates beneath the asphalt layer, pockets of air can form and cause asphalt to bubble.

100
Q

Where would you find information on rising damp within buildings?

A

BRE Digest 245

101
Q

Where would you find information on the diagnosis and treatment of Wet Rot?

A

BRE Digest 345

102
Q

Where would you find information on the diagnosis and treatment of Dry Rot?

A

BRE Digest 299

103
Q

What legisliation imposes a responsibilty on property owners in respect to Japenese knotweed?

A

Wildlife and Countryside Act 1981 - offence to plant or let grow JK

The Duty of Care Regulations 1991 - JK is a controlled waste and therefore owners have to dispose of it responsibly

104
Q

What methods of removing corrosion from steel frames?

A
  • Sand blasting
  • Shot blasting
  • Wire brush

APC (24 decks)

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