Pain-free flat roofs are easy to achieve

There are three main flat-roof systems: rubber, fibreglass and torch-on felt

Flat roofs can strike fear into the hearts of many people but they have come a long way from the problematic, leak-prone versions of the 1980s and before. Nowadays, a well designed and waterproofed flat roof should not cause problems or leak.

Most flat roofs are not actually flat: they have a slight slope to allow rain water to drain off. They are economical to build and allow homeowners to maximise floor-to-ceiling heights.

One of the most common problems encountered with flat roofs is rainwater outlets becoming blocked with leaves. To help prevent this you should allow for more than one outlet to drain an area and provide leaf guards to all outlets.

It’s wise to inspect your roof particularly in the autumn and clear them before an issue arises.


Poor workmanship is another source of problems with flat roofs. Before you employ a roofing contractor check their references and engage an engineer, or architect, to specify, detail and inspect the work.

There are three main flat-roof systems: rubber, fibreglass and torch-on felt. But how do they compare?

The cheapest of the three is the torch-on felt roof. But this finish does still carry a bad reputation from the older, and now unused, pour and roll systems of the past.

The new versions are far more flexible and durable. Three layers of felt are melt welded together with a large blowlamp or torch; hence the name torch-on felt.

The top layer is called a cap sheet which can either be in plain black bitumen, a solar reflective paint, or a mineral fleck which comes in a variety of colours.

Most have 10-year guarantees but a well installed torch-on felt roof could well last up to 30 years if looked after and treated well.

Foot traffic in hot weather may scuff the surface of a mineral finish which can lead to UV sun damage.

Rubber roofs have become popular in recent years. A rubber roof can often be installed in one complete layer without the need for joins, depending on size. It is an extremely light weight, elastic and tough finish. A well installed rubber roof should last 30 years upwards. They cost about 20 per cent to 30 per cent more than a torch-on felt roof.

It has a very durable finish and can be repaired easily, but repairs will be visible, as it normally involves gluing on patches, a bit like an inner-tube repair.

Fibreglass has been around for many years but has only gained popularity recently as a flat-roof finish. It’s normally laid in a one, or sometimes two, layer jointless finish with factory made trims and in any colour you like.

Most guarantees are for 25 years and it is no problem for this type of roof to achieve this if it is properly installed.

It is the most expensive of the three due to high material costs. It is very resistant to most forms of damage as it is extremely tough once cured.

Repairs are very easy and can be almost invisible. It is also by far the most attractive of the three options.