Flat Roof Materials

Any roof with a pitch below 10° could be considered ‘flat’. This is opposed to a pitched roof, which has a pitch above 10° and has a noticeable slope. The difference is important, as you’ll need to use different materials on a flat and pitched roof.

You’ll often find a flat roof on a garage, extension, or garden building. This is due to them being both easy and cost-effective to construct. Although, selecting a material for a flat roof can be a little more challenging.

Due to the low angle of a flat roof, you’ll need to use materials designed for low pitched applications. These materials will need to withstand challenges such as ponding water and debris build-up. 

Below are a few the best flat roofing materials. Each has been ‘tried and tested’ for decades, ensuring your roof is watertight and demands little maintenance. These choices suit various budgets and skill levels. 

EPDM

The most common type of flat roofing material is EPDM, a rubber membrane manufactured from ethylene and propylene. This membrane is fully waterproof, very tough, and incredibly long-lasting. 

Unlike other materials, EPDM can be easily installed by both homeowners and tradespeople. Once installed, you can expect your rubber membrane to provide a lifespan of up to 50 years with virtually no maintenance.

Fibreglass 

Another popular solution for flat roofs is fibreglass, a wet-applied membrane that combines glass fibres and polyester. This membrane is fully waterproof, easily maintained, and a long-term solution. 

In addition to offering a lifespan far shorter than alternatives, GRP supplies they can be far more challenging to apply. This is as the various resins must be formulated on-site and conditions must be perfectly suited.

Tar and Gravel

Whilst tar and gravel roofs are more common in the United States, you may find them throughout England, Wales and Scotland too. You build up multiple layers of tar and gravel to achieve a fully sealed, incredibly tough and low maintenance flat roof. 

By far the most difficult material to install, tar and gravel roofs typically demand the help of an experienced tradesperson. It is also accompanied by unpleasant smells and, in some cases, will demand several applications. 

Whilst the cost of flat roofing materials can vary, you can expect to spend between £10 - £20 per square meter. However, this does not take into account the labour costs or equipment associated with installation. 

EPDM and fibreglass membranes are widely considered to be the easiest material to install for both homeowners and tradespeople. Often making them the most cost-effective material with no specialist tools being needed either. 

Tar and gravel, on the other hand, is a far more challenging material to apply. You can, therefore, expect to spend far more on labour and, if undertaking the task yourself, also expect to invest in specialist tools for the job.

The lifespan of your flat roof is largely determined by the material used and the installation process followed. Whilst an EPDM membrane could last as long as 50 years, a fibreglass membrane could last as little as 10 years. 

To maximise the lifespan of any flat roofing material, it’s important to undertake regular maintenance. This is to prevent the build-up of debris, pooling water as well as other nightmare issues.

Roofs can see for traffic for all kinds of reasons, whether it be from roofers, window fitters or electricians. In these cases, it’s mostly larger, commercial or residential roofs. In this case, as is typical with larger projects, we would suggest Built-up roofing is the most able to bear the weight of regular traffic. That being said, EPDM roofs can also withstand LIGHT foot traffic.

The longest-lasting roofing material will typically be the one that is put under the least amount of stress and maintained the most regularly. That being said, there are naturally some built to last longer than others.

EPDM is one of these, with certain brands boasting life expectancies of over 50 years. This is much the same for GRP, with some touted to last up to a century. Of course, these claims can’t yet be validated.

At the end of the day, we would suggest focusing on individual products as they can vary from brand to brand.

A common question. But, the answer isn’t really as cut and dry as most would like. EPDM and GRP share a lot of similarities, the key difference is their durability. GRP does tend to be stronger, though it can also be more difficult to install. This means that while it may be suited to larger projects, EPDM remains a popular choice for a range of residential applications.

All that said, it really does depend on the product it questions. Some EPDM has been known to cover commercial buildings up to and over 300m squared.