Best Materials For Trafficked Flat Roofs?

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Flat Roof with Solar Panels being Surveyed by a Surveyor and Estimator

Best Materials For Trafficked Flat Roofs: We look at what is the best material for a highly trafficked flat roof?

Whilst its initial function has always been to ensure the building and those inside remain dry, warm and unaffected from the elements, the commercial roof has in more recent times become a favourite location for various plant, air handling units, PV and solar arrays, satellite dishes, terraces, pipework….. the list goes on.

This has resulted in an area usually infrequently visited, becoming one that receives much higher levels of traffic. Whether that be due to its transformation into a roof garden, or just the regular maintenance of plant. This inevitably puts additional strain onto the roof coverings. If this level of trafficking isn’t considered at design stage, there is a possibility this can contribute to premature failure of the roofing system.

Whilst all flat roofing materials and systems have difference advantages, some are far more suited to being regularly walked over than others. We looked into which are the most suitable, and the reasons why.

Liquid Waterproofing Systems:

Applied incorporating a base coat, a reinforcement fleece (fibre glass or polyester) and a top coat – liquid waterproofing solutions offer a whole host of benefits, in particular its flame free application.

However, most liquid surfaces are extremely slippery when wet, and if trafficked require the incorporation of anti-skid surfacing products.

Whilst each system’s specification will vary, on average the finished system can be anywhere between 0.6mm and 2.4mm in thickness. Liquid roofing systems are therefore more prone to puncturing than others, and usually require additional protection in the form of slabs or decking, as alone they are insufficiently durable to withstand localised pressure.

Single Ply / EPDM Systems:

Single Ply systems, as described in the name, involve the installation of a single layer of either rubber or a Synthetic Polymer. Such systems automatically have the advantage of being much more cost effective for large roof areas as only one “layer” is applied and therefore, are usually quick and easy to install. For this reason, such systems are extremely popular in new build constructions.

Much like liquid systems there is only one layer, meaning even a small incident can have significant consequences. It also shares the downside, that when wet is extremely slipper and requires a walkway membrane to be installed in addition to the waterproofing layer.

During maintenance the waterproofing is often abused (tools dropped, rubbish left etc.), and due to there only being one layer of membrane, it is easily punctured. Such systems, for reasons unknown, have become very popular with a variety of bird populations who will over a short period of time peck through the single layer.

Whilst single ply roofing can be an excellent solution in some instances, for highly trafficked roofs more suitable alternatives are recommended.

High Performance Felt Systems:

Roofing felt membranes are laid in several layers, giving greater durability, so they are far less likely to be damaged by traffic. Whilst many manufacturers offer a flame free solution, the most common method of application is still using an open flame which brings with it all the risks of hot works.

Modern felts are created using polyester reinforcement and modified bitumen, this greatly enhances the felts performance making it good to use in heavily trafficked roofs. The top layer of felt consist of a coarse “mineral” texture which greatly increases traction for those walking on the roof and protects from UV damage. Furthermore, most manufactures now specify an additional layer of felt to be laid over areas that are highly trafficked.

Mastic Asphalt

Asphalt combines an aggregate within it, so it is ideal for use when there is occasional access. However, in hotter conditions asphalt can become very soft and anything left lying on the surface will gradually sink into it, which in turn will cause punctures.

Therefore, contrary to popular belief mastic asphalt also requires protection or adaptation if it is to be trafficked regularly.


Whilst every roofing system has its benefits, when it comes to high levels of footfall build up felt systems and asphalt roofing are much more desirable than others.

However every roofing project has its unique challenges, and it is important to take all of these into consideration before being able to specify what the best approach should be. Our teams offer a number of complimentary surveys that can assist in putting together tender packages, so get in touch here to find out more.

This article, as with all other articles we produce, is for guidance purposes only. It does not constitute formal advice and should not be relied upon as such. For bespoke, unbiased advice relating to your commercial roofing project please contact us and we would be pleased to assist.

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