Building Pathology - University of London Flashcards
1
Q
Roofing condition survey methodology?
A
- Sketch area of the roof level, taking measurements
- Noting defects to all areas, including roof covering, upstands, hard standings (paving slabs), parapet walls
- Taking photographs of the areas and detailed notes to include in my report
2
Q
What did you check when undertaking your site inspection?
A
- Condition of the roof coverings, etc.
- Access routes to the building (central London) – assumed parking licenses required for works
- Safe access – requirement for scaffolding
- Location of compound and storage of materials
- Internal inspection to affected rooms below
3
Q
What are typical defects of a 1970s concrete building?
A
- Carbonation
- High Alumina Cement Concrete (HACC)
- Water ingress – crazed asphalt roof covering
- Alkali-silica reaction (ASR)
- Spalling
- Cracking
- Blistering
4
Q
What was the build-up of the roof?
A
- Concrete roof deck - screeded
- 20mm mastic asphalt applied directly onto screeded deck
- Liquid waterproofing system
5
Q
Why was replacement of the roofing cover proposed and not patch repairs?
A
- Various patch repairs including applied liquid across much of the building
- Severe UV degredation was noted across the roof field
- Roofing covering original –(1970s) so beyond its lifespan / economical repair
- 25-year guarantee of new roof covering will greatly reduce maintenance costs
6
Q
Why was a liquid system specified?
A
- Client budget allowed for a liquid roof overlay
- Easy application
- Building was in centre of London, so minimised space required to store materials
- Allowed application in hard to reach areas – plant/tank houses were on raised platforms on the roof level
- Fully bonded to substrate, so no glow paths for water
7
Q
Why did you specify to include insulation?
A
- According to Part L, consequential improvement stipulates you must increase thermal efficiency in line with building regs – 0.16W/m2K
- No insulation present, so roof likely to be poorly performing in respect to thermal retention
- To improve the thermal performance of the roof and improve the U-value
8
Q
Why did you allow the roofing specialist to specify the works?
A
- To obtain an insurance-backed guarantee of the works for 25-years
- Ensure contractor undertakes installation in line with the guarantee
- Roofing specialist will check each section of works and sign them off
- Liability falls on the roofing specialist
9
Q
What are the building regs / building standards a liquid system should be installed to?
A
- BS 8217:2005 -waterproofing
- BS EN ISO9002 – insulation
- Upstands (minimum 150mm height) – BS 6226
- Building regulations:
o Part B – fire safety
o Part L – conservation of fuel and power
o Part 7 – materials & workmanship
10
Q
Why did the existing roof fail?
A
- Roof was subject to blisters which occurs when the asphalt expands and pops through the surface due to higher temperatures in summer
- Crazing / cracking across the roof level allowing moisture into the rooms below
- Cracking to upstands
- Failure of patch applied liquid coatings
- Lack of maintenance throughout roof’s lifespan
- UV degradation over many years
11
Q
What other measures did you consider?
A
- Installing a felted roof, however was deemed as more labour intensive, various areas of plant / machinery on roof mean felt detailing much more difficult to achieve
12
Q
What internal repairs did you recommend?
A
- Internal plaster repairs – single layer of Gyproc to ceiling
- Replacement of ceiling tiles as was suspended ceiling
