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Flat Roofs – The Pros & Cons

The pros and cons of what to consider if you are looking to buy, or already own, a home with a flat roof.

In Victorian houses, flat roofs played a fairly minor role. However, jump to the present day, and while flat roofs have grown in size, this has not always been matched by improvements in quality.

flat roof house 2

Many homes have substantial flat-roofed extensions, with this there is a common misconception that the felt coverings have a life span of 10 to 15 years. Felt roofs of this age can continue to perform well, especially if the owner continues to maintain and protect them. However, all too often poor maintenance or lack of additional treatments such as gravel or solar reflective paint, as well as movement within the roof structure itself, can lead to premature failure.

Therefore, it is advisable that a flat roof be inspected twice a year, preferably in the spring and autumn, to arrange the clearance of leaves, debris and dirt that may prevent proper drainage or cause deterioration, and to identify at an early stage any signs of failure. Surveys should also be carried out after storms. This inspection should include the rainwater goods, valley gutters and rainwater outlets. It may be necessary to inspect flats roofs more frequently, if the internal use is moisture critical e.g. computer rooms, operating theatres, paper or document stores, telephone exchanges, or if the warranty/guarantee requires an inspection regime.

Here is what to consider if you are looking to buy, or already own, a home with a flat roof.


1. Flat roofs are generally less expensive to construct given the reduced areas involved.

2. The construction period is often shorter compared to traditional pitched roofs given their simpler style.

3. Access is broadly easier.

4. Internal space is not imposed on given reduced roof pitch angles.

5. Flat roofs are often considered more contemporary, aesthetically, than pitched roofs.


1. Flat roofs generally require a greater degree of maintenance – even more so if the surface is disturbed and damaged by people frequently walking over it.

2. Flat roof drainage is historically not as effective as traditional pitched roofs and standing water (ponding) can be an issue if falls are not adequate.

3. Typically, the life span of a flat roof is not as long as a traditional pitched roof – even less so if it is vulnerable to damage (points 1 and 2).

4. Successful sealing of flat roofs from water ingress can be problematic if not correctly executed.

5. Roof repairs are generally more expensive than traditional pitched roofs. The need for higher level of maintenance and more frequent and possibly serious repairs can only add to this.

If you are looking to use a flat roof for an alternative purpose, Graham Ellis, RICS Associate Director Residential says that unless “designed and built to be anything other than a roof, such as an integral veranda or patio, there are several practical issues that would be of concern”.

In short, Ellis advises: “Regardless of size, unless a roof has been specifically designed and built to accommodate a specified feature you should be prepared to go to a good deal of preliminary expense to satisfy the above points, and brace yourself for additional expenditure on top.

Reproduced courtesy of the Royal Institution of Chartered Surveyors (RICS).

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