What are the benefits of opting for a flat or a pitched roof for your extension?

In many ways it is a question of style and preference, but questions concerning ease of access, longevity and cost should also play a part in your decision.

The flat roof is not actually flat but set at a slight slope to allow rain water to drain off it. It consists of a horizontal base which is fixed to the ceiling joists with a waterproof membrane applied on top.

A pitched roof, on the other hand, is formed from at least two slopes that rise up in the centre to create a peak. It tends to be made from more durable materials such as tiles.

To help you decide on which is best for your extension let’s outline the differences and advantages of each click here to discover more options available to you and discover which extension is right for you.

Loft Conversion Styles

In recent years we have, to some extent, seen an increasing preference for pitched roofs over flat roofs. This is, in part, due to the desire for extensions to blend in with the existing look of the house.

Yet it is ironic that the turn to the pitched roof has occurred at the same time as flat roofs have been adopted by many cutting-edge architects to give buildings a contemporary feel.

Flat roofs do not have to be simply ‘contemporary’, however. An alternative to a conventional flat roof is a green roof that is covered in turf or natural vegetation. As well as being attractive this helps to protect the weather proofing of the roof and offers additional environmental advantages.

Flat Or Pitched Roof

Traditionally flat roofs have been constructed from asphalt or modified bitumen with a thin layer of gravel to protect the roof from the harmful effects of UV sunlight.

An increasingly popular choice of material, however, is Ethylene Propylene Diene Monomer (EPDM), a 3mm thick rubber membrane which can be applied seamlessly.

EPDM offers a lifespan of more than 40 years, compared to the 20 years offered by traditional materials.

The pitched roof is made from materials such as tiles that are more durable and weather resistant.


Flat roofing offers a more affordable option, although consideration for longer-term maintenance should be factored in. It involves considerably less materials and labour than a pitched roof.


Pitched roofs place a greater burden on the foundations of the building and this may have implications for the depth of the footings required. Whilst this is not of concern if you are building a new extension it can be a factor that comes into play if you are looking at replacing a flat roof on an existing extension with a pitched roof.


Pitched roof single storey extensions to houses can make access to upper windows and gutters more difficult for maintenance. This is not the case with flat roofs, although standing on them too much will impact on their need for maintenance.

Another thing to consider is that achieving the desired or necessary pitch for your roof can be complicated by the existing position of your first floor window. There are workarounds to this, such as altering the angle, including a recess or introducing a flat roof to the top of your pitched roof, yet they often will entail extra costs.

Planning Permission

There may be planning permission requirements that govern the height of your roof or the need to make it a pitched, rather than a flat, roof. These requirements may also determine the materials you can use on your roof.

Want To Talk Through Your Options?

If you are thinking of building an extension in the Brighton area and would like to talk through your options for the roof or any other aspect of your build contact us or why not give us a call on 01273 539124 or email us on [email protected]. We’re always happy to offer advice.

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