Building Pathology Flashcards
Level 1 - 3
Three different types of damp
Condensation, rising damp and penetrating damp.
How to identify the different types of damp (symptoms)
Rising damp: Areas that are physically wet to touch, Peeling wallpaper, Tide marks on the walls, Crumbling plaster, Rusty skirting board nails
Penetrating Damp: Noticeable localised damp patches in the walls, Poor plaster condition, Damaged decorations, Broken roofs, gutters, or leaking pipes, Decaying wood (indicating the presence of rot)
Condensation: Mould growth, Water droplets, Peeling wallpaper
How do you treat different types of damp
Faulty rainwater goods and drainage, Leaks from services, Penetrating services such as doors and windowsills, skirting boards. Condensation: Keep the building fabric above the thermal dew point, ventilation.
What are typical defects on a Victorian property
Lack of lateral restraint, roof spread, lintel failure and differential movement (particularly in bay windows). Rotten and Paint sealed windows, Poor thermal performance in roof voids, blocked air vents.
What is dry rot?
Dry rot or Serpula lacrymans is an environmentally sensitive fungus – though the term is a misnomer because the decay is invariably a result of damp. Dry rot is often found in areas hidden from view, such as under floorboards or behind a wall. If it is not identified early on, it can cause severe damage to timber and spread through the home.
What is wet rot?
Wet rot is the natural decay of timber due to high moisture levels. It occurs in timber with a moisture content of around 30%-50%, in contrast to dry rot that occurs in timbers with a lower moisture content of around 20%.
What are the causes of wet and dry rot?
The high amounts of moisture required by wet rot usually result from an external leak or water ingress from plumbing, guttering, stone pointing or downpipes. Dry rot is primarily due to a lack of maintenance and defects that allow water penetration into the fabric.
How do you treat wet and dry rot?
Wet rot: investigate and repair any leak before treating the rot itself to prevent recurrence. Once the moisture is removed, wet rot will stop growing. Typically, you will also need to replace the timber in the affected area. While dry rot can be treated with a fungicide, it is always best to have a surveyor assess the full extent of the damage. It may be necessary to remove plastering to investigate. As is the case with wet rot, you will most likely need to replace any affected timber.
What different types of cracks?
0 - Hairline cracks: Less than 0.1 mm in width.
1 - Fine cracks: Up to 1 mm in width. .
2 - Cracks easily filled: Up to 5 mm in width.
3 - Cracks that require opening up: Widths of 5-15 mm.
4 - Extensive damage: Widths of 15-25 mm.
5 – Structural damage: Widths greater than 25 mm.
What would triangular cracking above a window indicate?
Lintel Failure: The lintel may have failed or is under stress, causing the masonry above it to crack. This is often seen as diagonal or stepped cracks.
What is Regent Street disease?
It occurs due to the corrosion of steel frames within masonry-clad buildings. The steel expands as it rusts, causing the surrounding masonry to crack and potentially fall. Early signs are often masked by grime and pollution, making it difficult to detect until the corrosion is advanced
What is concrete carbonisation?
Concrete carbonation is a chemical process where carbon dioxide (CO₂) from the air reacts with calcium hydroxide in the concrete to form calcium carbonate. This process gradually reduces the pH of the concrete, which can lead to several issues like corrosion, durability reduction and shrinkage.
What are the limitations of a damp meter?
Indirect measurement, such as electrical conductivity can influence various factors other than moisture such as salts. Surface readings, which not accurately reflect the moisture levels deeper down and material variability. For example treated timber with walls with certain finishes can give misleading readings.
When would you use a borescope?
Borescopes can be used to inspect walls, ceilings, and other structures for signs of damage or to locate wiring and plumbing.
How do you identify wall tie failure?
Horizontal cracks along mortar joints as a result of the expansion of corroded wall ties. Bulging walls that may start to bulge or bow outwards due to the lack of support or any loose bricks that could be moving.
What is subsidence?
Subsidence occurs when the ground beneath a building sinks, causing the structure to settle unevenly.
What is Heave?
Heave is the upward movement of the ground, often caused by the expansion of clay soils when they absorb water.
How would you identify subsidence and heave?
Subsidence would have cracks in walls and sinking or sloping floors. Stiff doors and windows and gaps around window frames. Heave, would also have cracks in walls but may be wider at the bottom and lifting floors, with distorted door frames and external signs such as bulking or lifting external paths.
What is high alumina cement?
High alumina cement (HAC) is specialized type of cement known for its high strength and rapid setting properties, containing resistance to sulphate attack. Made popular from 1950 to 1970 and was banned following publicised collapses.
What is a common reason for leaning chimneys?
Sometimes, the chimney footing is either too shallow or isn’t set deep enough in the ground, which can cause it to crack under the chimney’s weight. Furthermore, footings made with substandard materials or construction methods are prone to cracking, which is a common cause of chimney tilting.
What causes rising Damp?
Lack of Damp-Proof Course (DPC) or deteriorated DPC. Porous building materials, poor drainage or clogged ventilation.
How do you identify rising Damp?
Tidemarks and damp stains, peeling wallpaper. Rotting skirting boards and white salt deposits.
What causes penetrating Damp?
Damaged brickwork or pointing can crate gaps for water to seep into structure. Leaky roofs can let water penetrate the building. Faulty Gutters and Downpipes can cause water to overflow and urn down the walls, poorly sealed windows and doors and external ground levels.
What causes condensation and how do you solve it?
Temperature differences and high humidity levels coupled with poor ventilation. Faulty windows and broken seals can allow cold air to enter.
What is the Due point?
Is the temperature at which air becomes saturated with vapor and can no longer hold all the moisture in the form of gas. When the air cools to thee temperature, the water vapor condenses into liquid water, forming dew.
What is cold bridging?
Cold bridging, also known as thermal bridging, occurs when a material with high thermal conductivity creates a path for heat to bypass insulation and transfer through the building envelope.
What are deleterious materials?
Deleterious materials, also known as prohibited materials, are substances that are unsuitable for use in construction due to their potential to cause harm or deterioration.
Give examples of deleterious materials?
Asbestos, Lead, High Alumina Cement (HAC), Chlorides, Organic Impurities, Clay and Silt.
What does a ridge dipping indicate?
Rotten timber joists
When was hi-illuminance cement banned?
Mid 1970s
What are common defects in parapets?
Water infiltration, spalling, cracking, displacement and vegetation growth
What do screeds curl?
Happens when water moisture evaporates from the top part of the surface, meaning it will shrink and dry faster than the lower parts of the screed.
What are the causes of rippling in floor coverings?
Moisture, Heat and Sunlight, Not allowing for a Perimeter and Hauling heavy objects over loosely laid vinyl flooring.
How do you test the strength of the screed?
The surface strength can be tested by scratching a 3 mm cross-hatched grid using suitable metal nail. If the surface flakes or chips-off, then the screed strength is insufficient and needs to be strengthened or in extreme cases, removed and levelled again.
What can cause a DPC to bridge?
Paths raised to a level very near a DPC (within 150mmm), can cause low level bridging externally
What is the difference between subsidence and settlement?
With subsidence, the supporting soil moves away from the structure taking away its support and allowing the structure to move. Settlement is where the structure moves the soil due to application of load.
How long can a removed tree affect the surrounding area
25 Years
What moisture content that beetles will like it?
Wood boring insects need a certain amount of moisture in timber of around 20% and higher to thrive.
What is sulphate attack?
Sulfate attack is a term used to describe a series of deleterious chemical reactions between sulfate ions and the components of hardened concrete, principally the cement matrix, caused by exposure of concrete to sulfates and moisture
Where does sulphate come from?
It occurs naturally in water in various amounts. If a high level of sulfate is in water, the water may have a bitter taste. Sulfates are also found in minerals, soil, rocks, plants and food.
What is concrete carbonisation?
Concrete carbonation is the result of an electrochemical reaction between carbon dioxide, moisture and calcium hydroxide that is present in cement, producing calcium carbonate.
What is the difference between sulphate and concrete carbonisation?
Sulphate is a reaction between sulphates and carbonisation is a reaction between carbon dioxide from the atmosphere and calcium hydroxide in concrete.
What is Japanese knot weed?
A tall fast-growing Japanese plant of the dock family, with bamboo-like stems and small white flowers. It has been grown as an ornamental but tends to become an aggressive weed.
How do you treat or remove Japanese knot weed?
Japanese knotweed is best controlled by the application of a suitable herbicide. Glyphosate-based herbicides are commonly used to treat Japanese knotweed. If glyphosate is applied correctly, at the appropriate time of year, it is possible to eradicate it, although it can take two to three years of repeated treatment.
Do bricks and concrete bricks expand?
Materials such as concrete, and cement products shrink over time after being placed in a building, whereas clay bricks expand slowly over a long period of time.
How would you repair carbonated concrete?
The reinforced bar must be descaled and cleaned ready for an anti-corrosion coat to be applied.
What is the Latin name for dry-rot?
Serpula Lacrymans
Where would you expect to find cold bridging?
Cold bridging happens when a warm surface or structure meets a colder one. Put simply it’s a weak spot in the insulation surrounding a house, known as the thermal envelope.
How does a carbide test work?
By mixing the sample and the calcium carbide together, any moisture within the sample reacts with the calcium carbide and releases an acetylene gas
What is the phenol test?
Compounds with a phenol group will form a blue, violet, purple, green, or red-brown color upon addition of aqueous ferric chloride
What are the health risk associated with lead poising?
Including increased risk of high blood pressure, cardiovascular problems and kidney damage
How do you encapsulate asbestos?
Encapsulation is when the ACM’s surface is sealed off so that fibres can’t escape. This may be done with paint, spray coatings, or other non-asbestos materials.
How do you treat cut-edge corrosion?
Applying corrosion-inhibiting sealants or tapes along cut edges and seams during installation. Ensure products used can adhere properly when metal expands and contracts.
How do you repair corroded wall ties?
Pushed through predrilled holes, a drill is used to spin the nut at the end, as the nut tightens the sleeves expand. Must only be used where brickwork is in good condition.
What different insects can cause damage to buildings?
Carpenter Ants and Carpenter Bees, Wood Boring Beetles and Termites
What common insects can cause damage to furniture?
Furniture Beetles
What are the acceptable moisture levels in different building materials
Timber, brick and plaster
How do you retrofit a DPC?
In existing structures, inject a chemical DPC at multiple points along the wall’s thickness to create a continuous barrier.
What is hydraulic lime?
Hydraulic limes (so called because they set under water) are made in the same way as non-hydraulic lime but using different limestone
What different types of underpinning are there?
Where would you use different lead codes?
How much should lead go into a mortar joint?
What are the main causes of building failure (generic)?
Poor workmanship, poor design
What are the 4 stages of the fungal attack lifecycle?
What causes condensation in roof voids?
When selecting a flat roofing material, what items should you consider?
When was the first trussed roofs introduced?
What is a jack rafter?
Tell me about thatch?
What are common defects in cavity trays?
Difference between overcoat and rainwater principle?
What is efflorescents?
What is designated defective housing?
Why would you underpin a building?
When do you need to prop in an excavation?
Any depth beyond 1.5m
How do you monitor cracking?
What is institutional condensation?
What diameter boreholes do beetles have?
What is a typical brick dimension?
How can you tell if word worm is live?
Frass, or test with tissue paper?
How do you treat wood worn?
Any weak timber should be removed and replaced with pre-treated timber. Affected timber should be chemically treated with Insecticides applied by spraying or injection directly target and eradicate woodworm larvae and adult beetles
How would you identify subsidence?
What is the worst type of wood worn beetle?
The house longhorn woodworm beetle
How does woodworm spread?
Woodworm spreads because adult female beetles will lay their eggs in the cracks of moist wood so that the eggs can be established safely. The larva will then burrow into the wood so that the initial signs of an infestation may be hidden. The insect can then live into the timber for 3-5 years whilst turning into an adult. The adult beetle then emerges and creates the holes you may see (emergence holes). Adult beetles will then mate, creating more beetles who will seek out further high-moisture timber in which to lay further eggs.
What causes woodworm?
The cause of woodworm is usually high-moisture content in your timber, predominantly sought after by adult female beetles in summer months so that eggs can be laid. The larvae then burrow, and when it exits, leaves behind the exit holes you commonly see.
How do you get woodworm?
The life cycle of woodworm larvae is roughly 3 years, which means your wood may have been infested before it was brought into your home.
What are typical defects you would find in a tenement?
Weathered and decayed stonework
Slipped, missing and broken slates
Poor repairs - use of cement mortar, flashband repairs
Lack of insulation in roof void
Debris in roof void
Timber decay
What are typical defects you would find in a modern property (Post-1919)?
Asbestos
Poor detailing
Defective rainwater goods
Water ingress
Timber decay
Poor ventilation
When surveying a roof what are some things you would look for?
Type of roof covering
Any missing, slipped or broken slates / tiles
Pitting of concrete roof tiles
Weathered leadwork
Open mortar joints e.g. to chimneys
Lack of capping to chimneys
Presence of underfelt / breather membrane
How would you identify failed render?
I would tap the render, if it sounds hollow then it is boss and has lost adhesion.
I would also feel the render and see if it could easily be broken away by hand.
What types of cavity wall insulation are you aware of?
Blown fibre insulation and blown EPS beads.
How would you identify if cavity wall insulation was present in a property?
I would check planning records for any information, however to be entirely sure I would have a contractor bore holes and then use a borescope to assess the cavity.
What is your experience of using drones to survey?
I have used drones to assess areas that are not readily or safely accessible through other means.
How would you identify the type of roof tile used?
I would look for any manufactures branding on the tile from a safe access point if possible.
How would you identify carbonation of concrete?
I would look for corrosive staining of the concrete as the rebar within may have corroded due to carbonation. I am also aware that a dye test can be used that turns carbonated concrete purple.
What is carbonation?
Carbonation is a process which happens to all concrete. Atmospheric carbon dioxide is absorbed by the concrete over time reacting with moisture over time to reduce the concretes passivity, lowering its PH value. Insufficient cover of rebar can result in corrosion, causing spalling and cracking of the concrete.
How would you treat carbonation?
Break out and hack away concrete, clean and treat the rebar with an anti corrosion coating and reinstate the concrete cover. An anti carbonation coating can also be applied for extra protection.
When undertaking a water ingress instruction what steps do you follow?
Have a conversation with the owner / occupier of the property to establish the details - when, why and how the ingress occurs.
Assess the area of water ingress internally and how it may relate to the external fabric of the building.
Survey externally, looking for obvious defects and follow a process of elimination e.g. are there any openings, defective rainwater goods.
Consider the evidence, reflect on finds and provide a possible cause.
Can you explain traditional construction to me?
Typically built on “footings” and not foundations in the modern sense using material that was at hand.
Walls are typically 600mm thick.
External leaf can be in stone or brick. Usually tied together by through stones and pre-determined points.
Cavity is filled with rubble and lime.
Inner leaf is typically brick with timber straps that take laths, thereafter plaster would be applied.
How would you identify the type of wall construction used?
I would look at the age of the building, typically most post 1919 buildings will of a mass masonry structure. I would also measure the thickness which would give me an indication. (600mm trad, 300mm cavity).
What are some typical defects you would expect to see with cavity walls?
Lack of or bridging of the DPC e.g. due to raised ground levels externally.
Cold bridges caused by poor workmanship e.g. snotters on ties.
Wall tie failure (have never seen but I am aware of this issue.
Lack of cavity trays and associated weepers.
When specifying a render system what would you do?
I would assess what is already in situ where possible measure thickness of the render cover and assess the wall build up. I would engage with a technical advisor (STO etc.) to assist in the development of a suitable specification.
How would you diagnose and report dampness in a bedroom with mould on the soffit?
I’d inspect the loft for ventilation issues or leaks. I’d use a Protometer to measure moisture levels. I’d recommend increasing insulation and sealing leaks to prevent future dampness, then document findings with photos in the report
What steps would you take if you suspect asbestos in roof sheets?
I’d stop any work in the area and recommend a certified asbestos surveyor for testing. I’d include safety precautions and further recommendations in the report.
How do you distinguish between condensation and other forms of dampness in a building?
Condensation typically occurs on cold surfaces and forms water droplets. I would check for signs such as mould growth in poorly ventilated areas, like bathrooms or kitchens. To diagnose, I would use a moisture meter and suggest improving ventilation or heating to prevent condensation.
How would you approach a situation where water ingress is occurring at a property?
I’d first inspect the roof, gutters, and flashing for defects that could allow water entry. I’d check the external walls for cracks or missing pointing. I would also check the drainage system for blockages. My report would suggest repairs to the affected areas and preventative measures to avoid recurrence.
What defects would you look for in masonry construction, and how would you assess their significance?
I would look for cracks in brickwork, bowing walls, or loose masonry. I’d assess the crack width and direction, as well as whether the cracks are stable or moving. A wider crack could indicate structural issues, so I would recommend further investigation and repairs to ensure stability.
How would you assess whether a building is suffering from settlement or subsidence?
I would look for visible cracks in the foundation, walls, or floors. If the cracks are wider at the base, it could indicate subsidence. I’d use a level to measure any uneven floors and recommend a structural engineer’s report for further investigation and any necessary stabilization.
What are the typical causes of dampness in a Victorian property, and how would you diagnose it?
Victorian properties often suffer from rising damp due to the absence or failure of the original damp-proof course (DPC). I’d diagnose this by inspecting the base of walls for signs of damp staining and use a moisture meter to measure moisture levels in the affected areas. Additionally, condensation may be an issue due to the original design having poor ventilation. I’d recommend installing a modern DPC or improving ventilation.
