Kitchen Extension Flat Roof - should they be avoided?

Historically most homeowners fear the use of flat roofs as a design solution for their kitchen extension due to previous bad experiences of leaks. However, this is now no longer applicable due to the advancement in flat roof coverings and workmanship.

I would never dissuade a client from using a flat roof for their kitchen extension and many are now in demand for that more contemporary or modern style of design. The only reason why flat roofs fail in today’s house extension market is usually down to cowboy builders or homeowners trying to do it on the cheap.

There are a few design issues to ensuring that a kitchen extensions flat roof works well for at least 25 years and the most important one, in my opinion, is ensuring a good fall to the roof slope and 1 in 40 should perhaps be the minimum. Avoiding complicated abutments and roof puncturing of service pipes etc, should also be avoided. Often, this is not always possible and good on site detailing by the final flat roofing specialist is vital.

Avoiding parapet wall up stands where the flat roof is hidden and below the perimeter wall of the kitchen extension is another design detail to be aware of. Having the top weathering system of the kitchen extension flat roof over-sailing the external walls is always the first choice but again due to design style requirements of the existing property or of the homeowner this may not always be possible or a popular choice.

The latest flat roofing systems suitable for a kitchen extension and are very popular come in three defied and separate materials:-

Polyester felts:- These are usually torch on applied and are very successful provided they are applied by an experienced and qualified roofing contractor. Usually a two layer system.

GRP liquid applied:- Modified polymers now very successful. 10 years ago they had problems of ‘reverse osmosis’ causing failures of the top matting but this has now largely been eradicated. System needs to be properly applied by an experienced and trained roofing specialist.

EDPM single membranes:- Developed in Germany and very popular in Europe. Slow to catch on in the UK because of restricting supply of materials to only trained technicians or roofing companies. Usually applied with adhesive or welding. Still more expensive than polyester felts in most cases.

Other flat roofing systems are also available for kitchen extensions but the above three are the most popular mainly due to ease of supply and a variety if installer available. Alternative coverings for a kitchen extension flat roof can be sheet metal cladding. There are a variety of systems and materials and many use folded upstand seams. Great if you desire a more commercial modern feel for your kitchen extension.