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Flat roof leaks and failures and how to prevent them

Flat roof leaks and failures and how to prevent them

Flat roofs have a reputation for being problematic and prone to leaks. SIG Design & Technology’s technical manager Steve Cleminson doesn’t agree and looks at the catalogue of problems revealed after a recent survey on a failing flat roof and how to easily prevent them.

The horror story
SIG Design & Technology were contacted recently by one of their main contractor clients about a failing flat roof they were looking at, so the company arranged a survey. The survey showed the roof had certainly been neglected. The working life of the asphalt had been shortened by a lack of care and poor design. The asphalt was age hardened and brittle, and as a result thermal and structural movement had led to splits and cracks, allowing water penetration. The roof had then been repaired using additional pieces of bituminous cap sheet and liquid treatments. These repairs had failed causing large blisters to appear, evidence of trapped air and moisture.

There were also large areas of ponding water, which causes several problems, including temperature variations between the ponds and adjoining dry areas, and freeze/thaw cycles in winter.

Outlets in the parapet which are designed to allow water to leave the roof were blocked with debris (including large pieces of timber) and silt, which had built up for so long that plants were growing in it.

How to prevent flat roof leaks
Due to the poor state of the roof thousands of pounds of damage had been caused to the building beneath and rather than consideration being given to an over cover, the proposal had to be for a full strip off and start again.

But could this situation have been avoided? Most definitely and in four simple steps:

1. Good Design
Maintenance is extremely important for all roofs, but maintenance programmes can be simpler and less onerous if the roof is properly designed to begin with. For example, there is a tendency to design flat roofs to minimums but designers should feel free to design at more than the minimum. They should design for a realistic, reasonable maintenance regime.

2. Installation by trained contractors
Most creditable suppliers run product specific training courses and ensure their products can only be purchased and installed by people who know and care that the installation is done right, meaning less wasted time following up on problems.

3. Planned, proactive maintenance
A roof denied an occasional inspection is storing up bigger problems for later. Have a good maintenance plan in place to avoid unnecessary and onerous costs.

4. Appropriate repair or replacement
No roof lasts forever, but a well-designed, well maintained roof can give a full life of service. On occasion, incidents such as falling debris, high wind or storm damage will need remedial treatment, and this needs to be undertaken using the correct materials suitable for the roof finish, properly prepared and applied by trained professionals.

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SIG Design Technology

SIG Design Technology

SIG Design & Technology is a part of SIG Roofing, a leading division of SIG plc, a FTSE 250 listed company and the UK's market leading specialist supplier to professionals in the building and construction industry. They design and supply flat roofing...
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T(01509) 505714
F(01509) 505475
E[email protected]
WVisit SIG Design Technology's website
 Mannheim House, Gelders Hall Rd, Shepshed, Leicestershire, LE12 9NH


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