Building Pathology Flashcards
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. For example, I instructed a drone survey of a high level parapet detail to assess its condition and found the render was weathered and open.
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. For example, I identified a Scotcem tile in this way during a roof survey of a tenement. You could also identify the profile of the tile.
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 talk me through how a steel framed building is constructed?
- Foundations - ground conditions will determine the type used, however, these are usually piled and capped.
- Steel columns are fixed to the pile cap / concrete slab.
- Steel skeleton frame formed using universal columns and beams. This frame takes the load.
- Permanent shuttering in the form of profiled metal sheeting make up the deck of the floor levels and is filled with cast in situ concrete forming the compartment floors.
- Normally light gauge steel studs form infill walls, weatherboard is attached externally and will carry a rainscreen or similar.
- Insulation envelope formed by insulating between light gauge steel studs.
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 working on coastal properties what should you consider?
- Wind driven rain, coastal areas tend to have less cover and are more vulnerable to inclement weather.
- Soluble salts - salts taken up from sea water and deposited during rain may accelerate decay of building elements.
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.
