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.
