EPDM Roofing VS GRP Fibreglass

July 17, 2019 | General
EPDM Roofing VS GRP Fibreglass

GRP or EPDM? It is a question that many roofers have been asking for years. With more and more people moving away from the traditional felt flat roofing types, due to the flame-free options available today, it really has become a competition between EPDM and GRP for which roof reigns supreme. 

So, if you’ve been wondering which type of flat roofing is best for your project, the flat roofing experts at Avenir Roofing have broken it down, to show you which flat roofing solution is right for you.


Flat roofing materials such as torch-on felt have been around for a long time. However, in recent years, it looks like roofers are turning towards the seamless, longer-lasting options such as EPDM and GRP because they have many more benefits.

Here are a few advantages that these two roofing types have in common:

  • Longer lasting than traditional felt and other flat roofing types. 
  • Flame-free installation
  • Highly weather-resistant
  • Can be fitted around skylights, vents etc.

What Are They?

EPDM (ethylene propylene diene monomer) is a synthetic rubber used to make roofing supplies. It is a single-ply roofing membrane which is popular for many small-scale roof applications, both residential and commercial. 

GRP (glass reinforced polyester), or sometimes known as fibreglass is a flat roofing solution made with extremely fine strands of glass which are woven together to create a flexible fabric. 

Weather Resistance

Both systems have the advantage of being seam-free, meaning they are very unlikely to cause leaks. Other flat roofing types such as felt and PVC have seams every few metres. These become weak points prone to leaks, which causes further damage to a roof. The seam-free application also makes both EPDM and GRP extremely watertight, which means they both perform well in wet weather.

However, when it comes to how the sun can damage your roof, EPDM is superior. When the sun shines on your roof during the day, it heats your roofing material, which then cools down on a night when the sun goes in. This causes thermal shock, where the roof expands and contracts. EPDM copes better which expansion and contraction, which also makes it more suitable for larger applications. GRP cannot be used on large roofing projects because the expansion and contraction rates can be excessive. 


Although both EPDM and GRP have the advantage of the flame-free application, they are installed very differently. EPDM is usually installed as one sheet which is adhered to a roof decking. It is glued using a wet bonding adhesive, with a stronger contact adhesive around the perimeters. After this, trims can be fitted to finish the roof, creating a neat and reliable finish. 

What’s more, EPDM can also be installed the DIY way, making it a more popular choice for ease of installation. 

GRP is installed using two layers of catalysed resin which go above and beneath a layer of fibreglass. This forms a GRP laminate which then requires a top coat resin to weatherproof the surface. This is a more complicated installation process than EPDM, which can put some people off. It takes longer and can only be carried out when the weather is completely dry.


When you compare the prices of EPDM and GRP, the difference is significant. EPDM costs much less because the materials used to make GRP are more expensive. You’ll also likely have to pay more for GRP since it takes longer to install than EPDM. 

There are a few more factors that you should consider when comparing prices of flat roofing types and not just the price at face value. Cost-effectiveness, which can be determined by longevity, also plays a part. While GRP usually lasts around 25 years, EPDM can last as long as 50 years, because it has been around longer. This makes EPDM very cost-effective, while its durability means you can expect little repairs through the years. 


Overall, both GRP and EPDM are aesthetically pleasing flat roofing solutions, so which one you prefer the look of usually comes down to personal preference. While they both have a very neat and tidy appearance, it is thought that GRP can look ‘plasticky’ because of the resin that is applied to the surface, whereas EPDM has a less shiny look.

If you choose your EPDM supplies from Avenir Roofing, you can get roofing trims that complement the colour nicely, and with the material being growth resistant, it will look great for years to come. 

When you get down to the nitty-gritty, it looks like there are many more advantages to EPDM over GRP. So, if you’d like to hear more about the EPDM available from Avenir Roofing, get in touch with our team today.

More articles from our blog…