Why Is A Flat Roof Slightly Sloped?

Daniel Bracewell • 18 January 2021
Flat roofs are an efficient, effective and attractive roofing solution, allowing for an extra living and dining space on top of your home. However, did you know that no flat roof in the UK is entirely flat?

Despite looking and indeed feeling like there is no incline, every flat roof in the UK has a tiny incline, as that is a legal requirement according to UK building regulations.

According to Approved Document Part H, the part of the building regulations that covers drainage on roofs, a roof must have an incline of 1 in 80. So for every 80cm of the roof surface, there must be a 1cm incline.

The reason for this is to ensure that rainwater effectively drains off the roof. Typically this comes from water rolling into a gutter on the side of the house, or in some cases from central drains that take water through the building itself.

Water that does not drain effectively can pool on the roof, which can cause several problems. If the roof is not adequately waterproofed, it can seep into cracks in the roof surface and cause leaks.

As well as this, in cases of severe rainfall, water can pool in large quantities, which can cause strain of the roof and potential structural damage if it cannot drain water away in any other way.

Drainage, even at such a tiny incline can help prevent this entirely, as can adequate waterproofing and sealing, and ensuring work is undertaken by flat roof specialists.
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