RICS APC Building Pathology — Questions and Answers
Question 1: What is the most common cause of rising damp in UK buildings?
- Roof leaks
- A failed or absent damp-proof course (DPC) (Correct answer)
- Condensation
- Burst water pipes
Correct answer: A failed or absent damp-proof course (DPC)
Rising damp occurs when moisture from the ground travels upwards through the building fabric by capillary action, typically due to a failed, bridged, or absent damp-proof course.
Question 2: What type of cracking pattern typically indicates subsidence in a building?
- Horizontal cracks along mortar joints
- Diagonal cracks that are wider at the top and taper towards the bottom (Correct answer)
- Fine hairline cracks in plasterwork only
- Vertical cracks in the centre of walls
Correct answer: Diagonal cracks that are wider at the top and taper towards the bottom
Subsidence typically produces diagonal cracks that are wider at the top (where movement is greatest) and taper downwards. They often appear near windows and doors where the wall is weakest.
Question 3: What is 'sulphate attack' in the context of building defects?
- Corrosion of metal fixings
- A chemical reaction between sulphates in bricks or soil and tricalcium aluminate in cement, causing expansion (Correct answer)
- Timber decay caused by fungal growth
- Damage to glass from acid rain
Correct answer: A chemical reaction between sulphates in bricks or soil and tricalcium aluminate in cement, causing expansion
Sulphate attack occurs when sulphates (from bricks, aggregates, or groundwater) react with tricalcium aluminate in Portland cement, causing expansion and cracking of mortar and renders.
Question 4: What is the primary difference between wet rot and dry rot in timber?
- Wet rot only affects hardwoods
- Dry rot (Serpula lacrymans) can spread through masonry and is more destructive, while wet rot remains localised to damp timber (Correct answer)
- Dry rot only occurs in new buildings
- There is no practical difference
Correct answer: Dry rot (Serpula lacrymans) can spread through masonry and is more destructive, while wet rot remains localised to damp timber
Dry rot (Serpula lacrymans) is far more serious because it can generate its own moisture and spread through masonry via strands, whereas wet rot (typically Coniophora puteana) remains confined to damp timber.
Question 5: What does 'spalling' refer to in brickwork?
- Staining caused by pollution
- The breaking away of the face of bricks, often due to frost damage (Correct answer)
- Mortar joints cracking
- Efflorescence on the wall surface
Correct answer: The breaking away of the face of bricks, often due to frost damage
Spalling occurs when moisture within the brick freezes and expands, causing the outer face of the brick to flake or break away. It is common in exposed, frost-prone locations.
Question 6: What is 'practical completion' in the context of building contracts?
- When all snagging is resolved
- When the works are substantially complete and the building can be occupied, even if minor defects remain (Correct answer)
- When the final payment is made
- When planning permission is granted
Correct answer: When the works are substantially complete and the building can be occupied, even if minor defects remain
Practical completion is the point at which the building works are sufficiently complete that the client can take possession and occupy the building, even though minor snagging items may remain to be resolved.
RICS APC Building Pathology
What is the most common cause of rising damp in UK buildings?