Expert Advice - Flat Roof Extensions







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Flat roofs have been given some bad press over the years, where they have often been associated with leaks and looking fairly unattractive. 

Built well a flat roof can have so many advantages, including creating a smart contemporary look as well as helping to keep the cost of an extension down.

We chat to Clarke Roofing, who share with us the benefits of a flat roof and what you should consider before incorporating one as part of your extension.

What are the main advantages of having a flat roof when building an extension?

The advantage of having a flat roof extension is that it is cheaper due to less materials and labour required and can be more easily designed to suit the space available. 

Plus of course flat roofs don’t encroach the space above in the way a pitch roof would which helps overcome some planning restrictions. 

Some flat roofs can also be designed as part of a terrace for upper floors subject to planning.

Green flat roof extension with a skylight by Clarke Roofing

How does the cost compare to a pitched roof - should I expect to save?

Yes – a flat roof extension is a lot cheaper than a pitched roof so cost savings can definitely be made. However, the visual appearance would need to be considered by the architect.

Are there a range of materials used to finish a flat roof and what are the options?

There is a vast range of materials available for flat roofs from hard metal such as Lead, Copper and Zinc to green and blue roofs as well as liquid plastic, built up felt or single ply membrane roofing systems. 

Metals such as Lead, Copper and Zinc have a contemporary architectural look, with blue and green roofs being environmentally friendly options. However, these types of materials are more expensive than the popular single ply membrane or built up felt.

The choice would be dependent on budget, building regulations and the required performance of the system. For example, blue roofs provide drainage solutions in an area where excess water can be an issue. 

Flat roof by Clarke Roofing using liquid plastic

Flat roofs used to be associated with leaks - how do I ensure this doesn't happen?

Yes, that’s right, many years ago they did have this reputation, mostly unfounded with leaks due to poor workmanship, but with many advances in flat roofing systems this has been dramatically reduced. 

We work with manufacturers such as Bauder, Proteus, Westwood and IKO to name just a few who check each stage of installation and offer up to a 25-year insurance backed guarantee. Our installers are all trained and have competence certificates for each manufacturer.

Is there any style of home where you wouldn't recommend a flat roof on an extension?

It really would depend on the property and surroundings. A flat roof extension wouldn’t necessarily look good on a listed building for example but we work alongside some amazing architects who work closely with the clients and local planning office and can come up with the perfect solution often using a combination of oak, lead and glass to a stunning effect.

What type of glazing is popular on a flat roof extension and should I ask my roofer or builder to install the glazing?

We at Clarke Roofing work with many window, skylight and roof lantern suppliers and are approved to install these as well as the roof itself. 

I would suggest that background checks are made to ensure the roofer or builder appointed has done that kind of work before. It has become very popular to have a rooflight over the kitchen area for example and these can have electric openings and led lights installed as well. 

All of the above must comply with building regulations.

Flat roof extension by Clarke Roofing - the rooflight adds height to the roof

Is there anything else I should consider?

Look at all the options available, contact your architect for advice on design, warm or cold ventilated roof and what materials can be used in your area. Consider green roofing for the environment but these must be maintained annually.

Always try and get 3 quotes and get written specifications and terms of guarantee. We would also recommend using an NFRC approved contractor too.

Published: September 29, 2022

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