Building Pathology Specific L2 & L3 Flashcards
What are common profiled roof defects?
Cut edge corrosion, fixings, condensation, expansion and contraction.
What causes cut edge corrosion?
Occurs due to the cut side of sheets, on the laps, are exposed to the elements and oxidises.
How do you treat cut edge corrosion?
Sand blast the corrosion from the cut edge joint, removing any peeling paint and feathering up the sheet. Provide a anti corrosion primer, provide a flexible fibre-reinforced membrane, provide top coat of paint.
How did you identify it was carbonation?
I noticed it was in specific areas within the construction to the concrete columns where leaks had occurred previously. This suggested that moisture over a period may assist in the carbonation of the area in specific areas, rather then additives through both sulphate attack and chloride attack, as it would be expected this occurring in more locations through additives. I carried out Phenophalein tests to ensure, and involved a concrete specialist to further confirm with lab tests.
How were you able to review costing for the schedule of condition?
BCIS
What causes salt efflorescence?
From hygroscopic salts through the mortar and water during the construction.
Why did the structure cause salt efflorescence on the internal face?
From hygroscopic salts through the mortar and water during the construction. This was not allowed to escape as the weep holes had been sealed within the structure and water travelling along the cavity tray into the property.
How did you provide defect rectification for the internal water ingress?
This was a contract management contract, as part of this we had no influence with the previous designs related to this and only brought in as QS on the project and separate scope of services in snagging final outcome. Due to the defect, I suggested a bulkhead to be installed so the water may escape.
How long does salt efflorescence usually occur for from construction?
Approximately 36 months.
What are the different roofing waterproof membranes for a flat roof?
- EPDM (Rubber): excellent properties, expensive.
- Bitumen (asphalt): cheap, provide hot and cold, requires coating on top to protect.
- Liquid Applied:
- GRP roofing:
- Single Ply membrane:
- Green roof:
What are flat roof defects?
Dependent on the roof itself, but in the case of bituminous felt roof:
- Crazing
- Ponding
- Blistering
- Poor workmanship
Why did you not choose to overlay the flat roof?
Currently, the property had no insulation within the roof. I decided to make it a warm roof due to this with tapered insulation and removing the existing covering due to the amount of water within the blisters.
You mentioned you were to replace the mortar, what did you specify?
I specified a 1:3 ratio with cement and sand.
Walls are typically 1:5 ratio.
Lime Mortar to allow breathability 1:3 or 1:5.
How did you identify the leaks within a building?
Electronic Leak Detection carried out by a specialist.
What is spalling?
Spalling is a term used to describe areas of concrete which have cracked and delaminated from the substrate.