Learn about EPDM and GRP flat roofing solutions here

There are a wealth of different roof finishes in the market, and for a flat roof, the top choices are likely EPDM and GRP. No roof is the same, and suitably, each roof finish comes with its own benefits and installation methods, so which one is perfect for your flat roof application needs?  

Factors to consider when weatherproofing a flat roof

When completing a roof, many factors are involved, firstly the shape, steepness and whether it is a cold or warm roof can affect how you choose the finish. Secondly, there are extraneous factors such as the regional weather climate, building regulations, and build time and cost factors.  

Further with a flat roof, your options are not the same as they are for pitched roofs. However, there are high-quality solutions you can choose from. EPDM and GRP flat roof systems are easy-to-install options that weatherproof the building and look great. These fantastic flat roof systems do not require heat curing applications like the torch-on method and provide protection against heat, water and frost. But you are probably wondering what the difference is and which one to go with on your next project.

Flat roof solutions

What is GRP?

Reinforced materials are not new, and have been around since the time of the Egyptians when they mixed straw with mud for durable building material. Similarly, Glass Reinforced Polymer (GRP) is a material that uses fine glass fibres to reinforce plastic or other polymers and cures into a strong and durable material. This is a durable product that weatherproofs the roof and also provides a sleek curb-side appeal. 

When to use GRP on a flat roof?

GRP roofing systems are used for flat and low-pitched roofs as there is no water and debris ingress when properly installed. The wet lay finish also allows for easy painting over fiddly corners and edges such as vents and roof lights, which helps to ensure improved weatherproofing. Using GRP for flat roofs on a housing development or commercial building is quite common as it provides a versatile solution that can be applied to almost any profile. This flat roof finish is so durable, it can also be walked on with minimal wearing, a feature that is preferred for rooftops that need maintenance access.

GRP flat roof finish with roof light

What is EPDM?

Ethylene propylene diene monomer or EPDM, is an easy-to-install single-ply rubber membrane that requires no special tools for installation. This solution is generally much faster than most flat roofing systems on the market and installers don’t need specialist roofing experience to install this to a suitable standard. There is also no need for heat application or lamination for the membrane to seal as it uses an adhesive backing.

ClassicBond EPDM flat roof installation

When to use EPDM for a flat roof?

Popular among roofers and DIYers alike, an EPDM flat roof is a top choice due to its low cost and ease of installation. It is perfect for weatherproofing low-pitch and flat roofs on small structures such as a front porch or garden shed, especially if it comes with Pre-applied Seam Tape (PST). EPDM can just as easily be installed on larger projects such as home extensions or schools as some variations can consist of one large piece that can be easily unfolded to cover bigger areas.

ClassicBond EPDM flat roof

How is a GRP flat roof finish installed?

When installing a GRP flat roof, otherwise known as FRP, (Fibre Reinforced Polymer or Plastic), you will need a complete system of components that are installed in a specific order. You can see a summary of the installation process below:

  1. GRP trims and profiles are used for the edge of the roof and are mechanically fixed to the roof boards. 
  2. Next, bandaging along the edge trims and fixings is needed to ensure water tightness. 
  3. Then, a mix of resin and catalyst is applied over the roof using a special roller for even coverage.
  4. After, a glass tissue overlay is cut to size and carefully placed evenly over the top – providing the reinforcement for the resin. 
  5. The fibreglass layer is then sanded to create a coarse texture for another coat of resin to lock onto. This completes the lamination process.
  6. After lamination, a topcoat needs to be applied. This topcoat can give the desired colour and provides another layer of weatherproofing and UV protection.

These elements may seem daunting, but for seasoned roofers are relatively simple to install when you understand the process. With full training and certification by Celuplast, you will quickly be able to complete a GRP flat roof that will result in a superior durable finish. Note, that depending on the size of the project, you will need to look out for the weather conditions as wet-lay systems cannot be installed in wet weather. 

GRP flat roof installation glass tissue
GRP flat roof installation

ProGRP installation images

GRP flat roof finish

GRP topcoat application

How is an EPDM flat roof finish installed?

EPDM systems are simple and quick to install as the whole process can be completed in just a few steps:

  1. After marking out the perimeter on the roof boards, (or existing roof surface), the membrane sheet is then unfolded to rest and put aside.
  2. If the EPDM system consists of one large sheet that is cut to size, a special adhesive is rolled out onto the surface and the sheet is stuck down gradually.
  3. In the case of an EPDM system with PST, the membrane sheets will be laid out exactly where needed, and the adhesive protection strip is peeled off each sheet and stuck down consecutively with the current sheet overlapping the last. 
  4. Lastly, edge trims are mechanically secured around the perimeter to create a watertight edge all around. 

This fast flat roof solution is a great choice when projects have small time constraints. With full product training and certification by Celuplast, you can be confident you are installing everything correctly while maintaining the product warranty. 

EPDM flat roof installation adhesive

ClassicBond EPDM installation image

ClassicBond EPDM flat roof installation

ClassicBond EPDM installation diagram

Product training

The GRP and EPDM installation steps above are for illustration purposes only. Each installation will differ depending on a number of factors, and we always recommend you undertake full training before beginning to use both the GRP and EPDM ranges. Any manufacturer warranties will be voided if training has not taken place.

At Celuplast, we provide full training and certification for our flat-roofing solutions* to ensure high standards and so the consumer can benefit from the product warranty. 

*new GRP product range coming soon

Which is the best option for flat roofs?

Both the EPDM and GRP flat roof systems can be installed by one person and when installed correctly can last for a long time. Both of these flat roofing finishes are durable, fully weatherproof and look great. Additionally, depending on the manufacturer, you can also expect a product warranty of up to 25 years so you don’t need to worry about the future performance of each system.

In summary, if you want a high-quality, highly versatile flat roof finish that can cater for large developments and you have the time to go through all the steps to install correctly, then the GRP flat roof system is a brilliant choice. However, if you are looking for a quicker alternative that still looks similar, then EPDM flat roof finishes offer the perfect solution.

Whichever you decide, we have a great range of GRP * and EPDM solutions in stock.

*product range may change, please contact us for up to date stock.

Classic Bond flat roof system

For more information about the systems, training or for trade prices, speak to a member of our sales team now

Submit your enquiry below and a member of our sales team will be in touch with you soon.