Building Pathology Flashcards
For the Walthamstow project when did you undertake an inspection of the roof space to paste the tissue?
Prior to Spring, Death Watch Beetles emerge in Spring to lay their eggs
For Walthamstow why does the woodworm infestation occur?
What is the lifecycle of a woodworm insect?
Invasive and survives using the woods nutrients, enjoys soft and damp timber.
Cycle of eggs, larvae, pupa and adult. Lay eggs in spring months. Growth can take up to 10 years, live a few months as an adult.
During your Westcliff project you said that areas of concrete had deteriorated due to carbonation, what made you know it was carbonation?
Concrete hammer test confirmed hollow areas, degraded concrete, phenolphthalein test colourless instead of pink showing carbonation, steel starting to corrode with rust apparent.
How would you repair carbonated concrete and corroded steel? what is the coating applied?
Break out concrete, clean reinforced bar and apply anti corrosion coat, repair concrete and apply anti carbonation coating to shelf angle. Priced for repairs up to 50mm in depth.
Resin based anti carbonation coating applied.
What reacts in the concrete with the carbon? How does carbonation affect the steel?
Carbonation converts the calcium hydroxide in the cement to calcium carbonate causing degraded concrete, the pH alkalinity to drop and steel to react by breaking down its barrier causing corrosion.
How do you generally ensure high strength and good quality concrete?
Vibrating and trowelling concrete and cube testing during construction. Allow to cure for required amount of time and QA checks.
What are the main features of Georgian / Victorian / Edwardian / 1960s era?
Georgian 1714-1830 - spacious with grand proportions, bricked up windows, three or four storey townhouses, sash windows, stucco fronted exterior, built around garden squares.
Victorian 1837-1901 - terraced housing, high ceilings, large windows, cramped, wood floor, high pitched slate roof, coloured brickwork, brick porch, narrow hall, bay windows, fire place, patterned wallpaper.
Edwardian 1901-1910 - Simple design, garden suburbs, roomy, bigger hallways, more windows, ornate details, red brickwork, mock tudor cladding, parquet wood floors, simple decorative features.
1950s/60s - weatherboarding cladding, boxy, low pitched roof, concrete roof tiles, fitted kitchens, open plan, vinyl floor.
What are the defects found in Georgian / Victorian / Edwardian / 1960s era buildings?
- Georgian - No DPC, snapped headers, poor restraint (no wall ties) so bulging walls, stone defects and sulphur attack, damp penetration through thin walls, timber lintel decay, stucco render cracking and water ingress, shallow foundations, lime plaster replaced with modern gypsum or cement which isn’t breathable, lead paint, asbestos, anthrax.
- Victorian / Edwardian - Sulphate attack to chimney, chimney support / breast removed, slipped or cracked slates, overloading of structure with concrete tiles, rainwater goods failure (corroded or blocked), no DPC, snapped headers, poor restraint (no wall ties) so bulging walls, removal of structural partitions, timber lintel decay, floor joist over notching, blocked air bricks / poor ventilation of sub floors, timber decay, built in timbers prone to decay, lead paint, asbestos and anthrax.
- 1960s - Wood wool and permanent shuttering, HAC, asbestos, cut edge corrosion, concrete chemical attack (carbonation), boot lintels (rotate forward due to load), brick slips to concrete frames and thermal movement, calcium silicate brickwork, mosaic tiles loss of adhesion, calcium chloride additive increases corrosion, Glass Reinforced Cladding (loss of strength), lack of movement joints, made up ground, removal of soil due to RWGs, asbestos, calcium chloride, nickel sulphate reaction.
For the Colchester gym building, why are movement joints installed?
Allows for expansion and contraction of the materials (heating causes this) and prevents cracking and damage
For the Colchester gym building, at what distances should movement joints be installed?
clay brickwork requires a movement joint every 10m and at least 550mm from end of wall.
For the Colchester gym building, how did you know the cracks were due to the expansion joints and not due to something structurally more serious?
- Cracks were vertical and along where the expansion joints should have been installed.
- There were no expansion joints even though wall was more than the 10-12m recommended.
- I inspected the building and could not determine any other structural issues, e.g. heave which would have had a different nature of crack.
For the Colchester gym building, why did you replace the bricks and not just undertake a repair?
- Bricks were fairly significantly cracked, more than hairline
- Replacement would ensure no structural issues
- Deemed marginally more expensive but worth replacing the bricks
For the External decorations project, what were the different door options?
- Repair
- Install hardwood timber door
- Aluminium door
- Steel door
- Fibreglass door
- Glass door
For the external decorations project, why did you recommend the aluminium door replacement?
- Secure
- Durable
- Recyclable
- Good thermal properties
- Cost effective in long term
- Resistant to weathering
For the Walthamstow project, what size emergence holes would you expect to see?
honeycomb appearance and 3mm diameter holes.
In regards to the Walthamstow project, how do you prevent reoccurrence of an infestation?
- Specialist engaged to terminate woodworm
- Apply incesticide to timbers
- Repair timber as necessary and engage structural engineer if necessary
- Improve ventilation to ensure completely dry timbers. Install eaves ventilation or roof tile ventilation.
What are other woodworm infestations? How did you know it was the Death Watch beetle
Common furniture beetle, house longhorn beetle and wood boring weevils.
Death watch beetle is medium sized and brown with hairs, they form 3-4mm holes and tapping can be heard in the night.
What type and location of crack would indicate heave?
Heave cracking is more likely to be vertical, whereas subsidence is likely to be diagonal.
Heave cracking likely to be wider at the bottom and thinner at the top
What are the limitations of a damp meter
- Damp meters are misused, defects are not rectified.
- Conductivity issues with metal studwork.
- May require recalibrating.
- If not reading wood will need a WME reading.
What are the characteristics of dry rot?
- Brittle and cuboidal cracking
- Lower moisture content of 20-40%
- Extensive and can spread to masonry
What characteristics determine infestation of death watch beetle?
- Medium sized brown beetles
- Tapping in wood at night
- Flight holes 3-4mm wide
How often should expansion joints be installed? How may this vary depending on materials?
Clay brickwork - 10-12m
Lightweight concrete block - 6m
Parapet wall masonry - half the above spacings and 1.5m from corners
Why are would a DPC under the coping stones prevent water ingress?
DPC prevents downward transfer of moisture into the wall.
As well as a hammer test, what else could determine carbonation?
- Observation
- Phenolphthalein test pink to colourless a sign of carbonation
What was your advice to the client to resolve death watch beetle infestation?
Exterminate the infestation with specialist to apply insecticide and inject.
Timber repairs or replacement may be required.
Since timbers were around 20% and at a level which was okay but slightly high, improve ventilation with fascia ventilators rather than roof tile ventilators which are installed by puncturing the roof membrane or air purification unit.
Fascia ventilators both sides for cross ventilation, refix fascia board 15mm below, nail to top of fascia board, refix gutter and gutter bracket spacer, relay underlay and roof tiles.
What would be the prognosis if the death watch beetle was left?
Continue to multiply and damage the timbers and eventually lead to structural damage.
Why did you recommend replacing the brickwork for the gym building? Could repair have been implemented?
Replacing the brickwork was recommended because they were cracks in excess of 2mm. It was not a huge amount of bricks and therefore the cost difference between repair and replace was not huge.
How were you able to determine that manufacturing issues had caused the water ingress?
I measured sample windows which were removed and found that the window measurements were not correct and did not fit the window openings. This combined with installation issues had caused the problems.
Were measurements undertaken during replacement of the windows because within the report you then stated for all windows to be replaced?
Measurements were undertaken of sample windows replaced at different plots and thereafter once a representative sample was obtained it was specified for all windows to be replaced.
How can you differentiate between wet rot and dry rot?
- Undertaking moisture meter readings
- Feeling whether its soft and spongey
- Observation as to the area it has affected
How do you differentiate between penetrating damp, rising damp and condensation?
Condensation – black mould spots on walls, damp smell, water collecting on windows, lack of ventilation.
Penetrating damp – bigger after rain, staining patches, black mould, grow in size.
Rising damp – tide marks, 1 metre, yellow / brown colour, salts present.
How does rot occur? How can it be eliminated?
- It is caused by a fungus that is attracted to wood and feeds off the timber, destroying it in the process.
- Stop water source, treat timber with fungicide and repair, improve ventilation.
Identify the main causes of movement cracks? What do different cracks look like?
Subsidence - run diagonally and are wider at the top of the crack.
Heave - likely to be vertical or diagonal cracks and wider at the bottom.
Settlement cracks - vary in width and direction.
Differential settlement - cracks occur along line of differential settlement.
Insufficient expansion joints - occurs vertically and can be where joint should have been installed.
What different factors can cause subsidence and heave?
- Pipe leak or rectification
- Water table rise or fall
- Tree planting or removal
- Ground movement
Identify equipment you may require for a survey?
Torch
Camera
Spirit level
Notepad
Phone
Disto
Tape Measurer
Tape Gauge
Damp meter
Identify the main types of building survey and the practise statement that sets these out?
Level 1 survey - condition survey
Level 2 survey - homebuyers survey (possibly w/ valuation)
Level 3 survey - full technical building survey
Home Survey Standard 1st Ed 2019
Why does metal studwork cause electrode interference? In what other situations does it have limitations?
Conductivity of studwork may affect readings between the prongs.
Limitations in rising damp, if defect is not identified and if not recalibrated correctly.
What factors have affected building appearance?
- Material availability
- Technological advancements
- Preferences or zeitgeist
- Cost competitiveness
- Legislation
Why do you return in Spring to check the tissue for the Walthamstow project? What is the lifecycle for the death watch beetle?
eggs, larva, pupa, and adult. In Spring they emerge and lay their eggs and this is when they will leave flight holes.
What was the cause of water ingress to the gym ceiling?
DPC not installed underneath the coping stones meaning that water was able to penetrate down the cavity, access the building envelope and cause staining.
