Building Pathology Flashcards
What are typical defects associated with Georgian Properties?
Damp
Roof Defects
Walls
Foundations
What are the common defects to a Georgian Building Wall?
Penetrating damp due to single skin wall
Frost Damage
Sulphate Attack
Spalling
What are the typical defects to a Georgian Building Roof?
Roof spread
Roof Sag
Defective slate tiles
Can you name steel related defects?
Rust
Corrosion
displacement
What are the main components in a Victorian Roof?
(top down) Slates or tiles Underfelt (in late Vic era) Ride plat Rafters Purlin Ceiling Joists Wall Plate
What are the typical defects of a Victorian Roof?
Roof sag roof spread rotten timbers delaminating slates defective valleys defective flashings
Can you explain interstitial condensation and where it can be found?
Condensation which occurs between building elements
Can be found in cavities
Cold roofs
Defective double glazing
On Sadler House what kind of sealant did you recommend?
This was specified in accordance with the Weber light weight render system.
What are the tell tale signs of rising damp?
Horizontal tide marks, peeling paint or plaster
What remedial works did you specify for 47 David Place?
DPC was shattered and i specified an injected DPC
Down pipe discharging onto paved area where damp was located, this was relocated.
What remedial works did you specify for the external cracked areas to 47 David Place?
Just under 5mm i specified pointing up with lime mortar.
What are the common victorian walls?
solid or cavity
How would you identify if the victorian wall has a cavity?
This was be approx 20-30 mm thicker than a 230mm solid brick wall.
Can you inject insulation into a Victorian
No the gap would need to be at least 50mm.
What are the three common defects to masonry in Vic buildings?
spalling
frost
sulphate attack
What is the tell tale sign of frost damage in brick work?
spalling surface
How would you repair spalling brickwork?
Depending on severity, remove brick with all saw and reinsert the other way around.
Rebuild with lime mortar and pigments
If not reparable replace with appropriate porous brick.
Why is remediating Victorian walls with lime important
lime is breathable whereas modern cement is not
What is the typical defect at the end of a Victorian terrace?
leaning
Why is leaning a typical structural defect to victorian buildings at the end of a terrace?
Because the side wall often has little restraint.
What is the typical construction of a Victorian Building Foundation footing?
This would be a stepped footing.
Relating to Victorian Buildings describe a stepped footing?
Trenches are approx 450mm deep and the foundations are layed with bricked starting 700mm in width decreasing as they extend up.
Describe load bearing in some common soil types? (four types)
Chalk and rock are firmest.
Sand and gravel have good characteristics
Peat is poor
Clay is good but subject to shrinkage and swelling.
Describe the process of shrinking and swelling to clay soil?
Wet periods clay swells, whereas in dry periods clay shrinks and cracks.
What is the difference between subsidence and differential settlement?
Subsidence is caused by a change in the soil load bearing capacity or differential movement due to the varying depth of foundations.
Settlement is when the building moves as a whole when first built.
What is the most common cause of subsidence?
Tree related.
What is the problem with removing a tree which is close to a building?
The sub-strata may swell and cause heave.
What are the options for managing a tree which causes high amount of shrinkage?
Pollarding or Heavy pruning.
What is the problem with underpinning a terrace block of Victorian Buildings?
This is likely to move the subsidence to another area. An alternative option would be to pollard the area, if possible.
What are the common roofs types in victorian buildings?
Pitched, butterfly and lean too.
What is the sequence of operation of a pitched roof (detail)?
Top down
slates/tiles
underfelt.
The roof structure is ridge plate rafters battens purlin strut binder joists wall plate.
What is the risk of insulating the roof in victorian buildings?
Reduces breathability and increases the likelihood of rot and mould.
If recommending a roof covering to a victorian building what would you consider?
Structure. Victorian buildings roof timbers were installed sparingly which works for light slates, however if heavy concrete tiles are installed it will likely lead to roof sagging.
What makes Welsh slate identifiable?
It has a grey purple hue.
What defects are common at flashings?
Concrete fillets spall and lead to ingress. Vegetation growth.
Defective lead detailing
What would you suspect for a sagging roofs?
Poorly cut rafters, purlin deflection.
How would you remediate week roof timbers?
Strengthen roof timbers.
What defect would you expect for roof spread?
I would expect the ceiling joists to be inadequately fixed to the walls.
What would you expect for a leaking victorian roof with slates?
slipped, missing or damaged slates.
How would you go about remediating ingress to a victorian roof with slates?
Assess how many slates are defective. If only a few require remediating I would recommend replacement of those. If there is widespread delimitation blistering I would recommend whole sale replacement.
Explain the facade and ingress failure at Sadler House?
No primary joint sealants at window.
External Render had significant spalling and cracking.
What were the cladding defects on Windward House?
The cladding showed signs of sea/air borne pollutants
The actual cladding was not in poor condition however it lacked routine maintenance.
What type of insulation is at Windward House prior to the work?
This was a Expanded polystyrene.
What insulation type did you consider for Windward House and Liberation House?
This was a phenolic system.
What are the disadvantages and advantages of a phenolic insulation system?
Strength and Structure Heat resistance Moisture resistance Fire performance Recycling
Disadvantage is that it is more expensive
What is the advantage of a tapered insulation system?
Pre determined falls are achieved via off site manufacturing.
What are the four types of damp?
Condensation
Rising Damp
Penetrating damp
Flooding
Explain condensation?
water vapour changes to liquid
When hot air touches a cold material it reaches its saturation point and turns to moisture
Where is condensation common?
WC
Kitchen
Explain penetrating damp
This is rain penetrating through building structure as a result of capillary action
Explain a situation where you have come across penetrating damp.
A single skin wall which had been remediated with modern cement had penetrating damp. The likely cause was because the building wasn’t breathable and there was no ‘second skin’ to act as a barrier.
Explain rising damp
Moisture from below ground wicking up the building.
This is common in buildings built before the Public Health Act 1875.
What are the two primary issues with moisture metres?
1 they don’t measure moisture in masonry
2 dependant on probes having good connection
How does a calcium carbide test work?
Brick or plaster samples are placed in a pressure cylinder along with calcium carbide. If moisture is present it will react to form acetylene gas.
What other options are there was testing moisture content of masonry.
Gravimetric test.
What were the defects in the Consultants report for Windward House?
External debris and contamination from pollutants on Granite Rain Screen Cladding.
How is the Rain Screen Cladding attached at Windward House/Liberation House?
Thermal Break Sub-Structure Vertical Rail
Can you draw a detail of the ‘Thermal Break Sub-Structure Horizontal Rail’ at Liberation / Windward?
Connections by SE to reinforced concrete wall
Vertical Wall Bracket with Metal Stud connection to cladding panels
https://www.monarchmetal.com/cladding-rain-screen-systems/wall-brackets-substructure-components/
For Windward House roof what was contained in your own Defect Analysis?
Multiple areas of torn single-ply membrane
Balooning of the single ply caused by lacking bond and negative suction pressure
Parapets fixings were not effective
Lightning protection system was defunct
Connection details at Stanchions were debonded
No routine maintenance/heavily soiled
On Windward House what did the Calcium Carbine results show (express in measurement reading)?
This showed H20 to Wet Weight (H20-/w/w) was 1
What are the safety consideration with the Calcium Carbide Test?
Acetylene gas formation on contact with humidity.
Stay upwind
Keep others away
Shut off ignition sources
For Windward House what was the defect with the lift?
The Landing Operating Panel had failed because of water ingress.
At Windward, how was the roof bonded?
According to O&M related literature this was a factory pre applied adhesive.
For Windward House, what are the advantageous and disadvantageous with Patch Repair?
Pros Lower cost Fast Meets incoming tenants requirements Time frames mean no MIC 2016 additional costs
Cons
No product warranties
No collateral Warranties
Not as reliable
For Windward House, what are the advantageous and disadvantageous with whole sale replacement?
Pros
25 year product warranty
Collateral Warranty
Reliability
Cons Expense Additional Time frame requirements (consultants and programme, planning and building approval) Sensitivities with tenants in situ Scaffold
For Windward House, what is Part 11 and what are the implications you advised to your client?
Part 11 is Conservation of Fuel and Power
My advice was that if a wholesale repair was to take place, this would require upgrading of all roof insulation elements to modern requirements of 0.18W/m2k.
How would you manage Japanese knotweed?
Control (herbicide) not suited for areas where regrowth can be an option like construction sites
Removal
What is the difference between dry and wet rot?
Wet - Excess of water normally black and fungal growth in timbers
Dry - Growth in 20% moisture content
What are the advantages and disadvantages of concrete framed buildings?
Pros Tension and Compression is good Modulability (formwork) Cheaper compared to steel Low maintenance Fire resistance
Cons High embodied energy Heavy (foundation requirements) Lots of formwork Time
What are the typical defects found in a flat roof?
Blistering Thermal Movement Exposed Layers Poor quality flashing Heavy soiling
Cold roofs have interstitial condensation
How does a crack monitoring ‘tell tale’ work?
This is a glass plate or a two two layered plate with a red x in the middle which indicate movement. The later is better as it provides indication of how much movement.
What types of damp do you get in buildings?
Rising
Penetrating
Condensation
Internal leaks
What are the typical causes of damp in building?
No DPC
Single skin wall
Leaks in plumbing
Cavity walls - mortar snot causing bridging or poor quality/defective wall ties
What causes concrete failure?
High levels of chloride (common in roads heavily salted to prevent ice)
Carbonation
Freeze Thaw deterioration
What is carbonation?
When carbon dioxide from air penetrates concrete and reacts with hydroxides - causes spalling
Where might asbestos be found in buildings?
Roof - sheets, tiles
Boilers - lagging, paper linings
Ceilings - spray coatings
Interior walls - partitions, panels, insulation
Floors - tiles
What types of timber decay are you aware of?
Dry rot (serpula Lacrymans)
Wet rot
Wood Beetle
What causes timber to decay?
Dry rot - moisture content of 20% caused by humidity and thrives at around 23 degrees
Wet rot - moisture content above 25% and a continuos supply of moisture
Beetle attack (Death Watch / Longhorn)
What types of building movement are you aware of?
Differential Movement
Settlement
What is rising damp?
When high levels of damp at ground floor level move upwards in capillary action. Buildings built prior the 1875 Public Health Act should be carefully assessed for rising damp.
What is high alumina cement and why is it problematic?
This is manufactured with limestone and bauxite.
When it sets it gives off high heat and becomes porous and weaker.
Where is high alumina common?
Due to rapid hardening
- Marine construction
- Sewer Infrastructure
- Concrete buildings (1950s-1970s)
How can you identify high alumina cement?
XRF test BRE for further guidance
Do you always use a damp meter on inspections?
I always have it with me however it is not Appropriate to masonry and timbers with metal beading, for instance around windows.
What are the limitations with a borescope?
Poor visual site
L2 - Can you provide an example where you identified interstitial condensation? What were the symptoms and damage?
La Pulant Sea Breeze
1970 apartment block with flat roof covered with a mastic asphalt covering
Cold roof.
The ceiling had significant damp lines at 400m centres which indicated damp joists. The moisture meter was indication 20% indicating dry rot
L2 - At Sadles was the water ingress restricted to areas adjacent opening? Explain what you saw when you visited site for the first time?
On the majority yes. There was sporadic damp patches and the moisture readings were high. Mould spores were also present and decorative finishes were peeling at all fixed openings.
Also, locations corresponding with external cracks.
L2 - On Ldubs, how did you identify there was pooling beneath the single ply roof covering?
Originally the re-roofing works did not include for replacing the insulation however when removing the defunct single ply membrane i inspected the open cell insulation which was significant damp, when removing and look below there was significant amounts of water. I inspected 12 locations all the same.
How does steel corrode?
Oxygen and Moisture
Chloride Ions salt (sodiem chloride)
What is the method of assessment for assessing corrosion activity?
Visual (Rust) Sound (Hammer test) Thickness (Cover to steel) Chemical (Chloride levels) (Carbonation test) Potential Mapping
L2 - Why did you believe that a protimeter would fail to yield accurate results?
Do not work with masonry. Only carbide or speedy test it accurate.
L2 - At DaVe P, where did you identify tide marks?
Internal wall (Early Cavity)
What is a category three crack?
These are cracks up to 5-15mm or several 3mm cracks.
What information did you seek regarding the cracks at D Place?
How long have they been there?
Are they getting larger?
Are they increasing in number?
L3 - At Sadler House, why was the render in poor condition and how was this allowing damp to penetrate?
There was cracks. Also, render had spalled exposing the reinforcing mesh and subsequently the insulation.
The Weber tech doc states that movement joints should be installed - this was another defect with the installation. The movement joints enable some movement.
What patch repairs did you advise to the render?
The clients requirements were low cost, my research indicated that a Weber PM system (advise from manufacture) could be installed to repair the render which included a 9 year guarantee (if installed by approved persons)
What timescale did you expect the remedial works to last for?
Manufacturer states 9 years,
Dependant on maintenance and latent defects
For Sadles did you consider any other remediation options?
Whole sale replacement
How do you believe the single ply membrane had torn at Windward House?
Wind suction - heavily exposed
Of the two solutions for Windy, which do you believe is the better option? (discuss pros and cons as this was another question)
That depends on cost, time quality.
The patch repair was beneficial because it enabled no impact to the tenant moving in below, however this is only a short term repair and the disruption is basically postponed.
The wholesale repair would provide guarantee and collateral warranties for 25 and 6 or 10 years, respectively, which provides far greater quality and the associated benefits of bolstering the price if the client wanted to sell, as well as providing surety to the tenant in the long term as well as a considerably more solid O&M file.
What were the implications of water ingress to the lift shat?
The tenant did not want to repair this until the roof works were complete.
Are all cracks in reinforced concrete an issue?
The steel beam is for tension (bottom face)
Concrete cant carry tension so for concrete to work it must crack slightly.
What other safety factors could be compromised if you find a crack?
Fire
What tool do you use to measure a crack?
Crack width ruler
What can cause a building to crack?
Ground movement
decay of building fabric
thermal
ground
What is the burland table/BRE 251?
Crack assessment
L2 -What does a typical DPC look like and what the one a Dplace?
The one at Dplace was two courses of slate. The outsides were in poor repair with cracks. It was surprising that the slates were protruding from the wall as other buildings in a similar era had these embedded in mortar.
A typical DPC should be at least 150mm above ground level.
L2 - How did the slate at Dplace shatter?
There were signs of building movement but these fragiles slates are common to cracks as there are brittle.
L3 - At Sadles - where was the joint sealants lacking? What type of sealant did you advise to the render?
There were primary joint sealants. There was secondary damp proof layers at the junction of the windows but because almost all windows has a a gap between the window frame and the opening there secondary seals were unable to cope with the amount of water.
L3 - What patch repairs to the render did yo u advise?
These were in accordance with the manufactures directions, this was a Weber system and i liaised directly with the manufacturer who advised on the correct product for this remediation. This was a light weight render system which could be applied on top of the the current render, it also included a filler to conceal the cracks.
L3 - What timescales did you expect the remedial works you advised would last for?
9 years as this was a product gaurantee. Although it would be important to note that appropriate routine maintenance should be applied.
L3 - Did you consider any alternative remedial works to Sdles?
Wholesale replacement although this would be significantly more expensive it is however worth noting that the EWI systems can come with 25 year warranties and can make the building very attractive if the client wished to re gear leases or was looking to sell.
L3 - How do you believe the single ply membrane at Windward House had torn?
In some instances i know that it had torn because of wind suction and uplift but there was locations which made it very unclear as to how it had torn. For instance, there was a 1m tear almost directly in the centre of the roof.
L3 - Of the two solution you provided to the client to Windy, which did you believe to be the better option ?
PRos and cons?
The patch repair had the potential to keep the building watertight straight away and it matched the KPI required for the incoming tenant for the time required.
However, the plant required replacement and the patch repairs would only last a small period of time in comparison to long lease, I imagine that the short term repairs were dictated upon the funds short term repair requirements.
L3 - What were the implications of the water ingress to the lift shaft?
health and safety risk but the lift was decommissioned and required a control panel replacement. The roof required repairs as a matter of priority prior to the lift being fixed.
L1 What is the difference between wet rot and dry rot?
Wet rot has high humidity and will appear brown in colour.
Dry rot has a silky white surface
L1- What defects and deleterious materials would you associate with Georgian (1775-1849) buildings?
No DPC
Timber lintels (timber decay)
Shallow foundations
Lime plasters replaced with modern gypsum cement which was bot breathable.
Asbestos Animal hair (anthrax) Lead Paint
L1- What defects and deleterious materials would you associate with Victorian buildings (1840-1900)?
Chimney Support removed
slipped or cracked slates
overloading structure
No dpc
Timber lintels decaying
block air bricks in floors / poor ventilation of sub floors
Asbestos Animal hair (anthrax) Lead Paint
L1 - What are the associated defects of a timber frame?
Excess moisture / damp can lead to structural degradation
Risk of insect or fungal attack
Risk of fire spread (alleviated by appropriate fire codes)
Differential movement between brick skin and timber frame.
L1 - What are the associated defects of a concrete structure frame?
High levels of embodied energy
Restricted design
Weight - foundation requirements
Quality and corrosion issues
L1 - What common flat roof coverings are you had experience of?
Single ply -(con - foot traffic and shrinkage0
mastic asphalt (con - no solar reflective coating)
Copper (con - reaction to pollution)
