No products in the basket.
When installing an EPDM flat roof, choosing the right adhesive for each part of the roof is just as important as choosing the membrane itself.
Two of the most commonly used products are water-based deck adhesive and bonding adhesive. Although both are designed to secure EPDM membrane, they perform different jobs and aren’t simply interchangeable.
So, what’s the difference – and where should each one be used?
Water-based deck adhesive is primarily designed for bonding EPDM membrane across the main field area of a suitable roof deck.
A good example is Roofer’s No.1 Waterbased Deck Adhesive, designed for bonding EPDM membrane to suitable timber roof decks.
For a typical domestic EPDM installation over a suitable deck such as OSB, the adhesive is applied across the main roof area before the membrane is carefully laid into position.
Typically, water-based deck adhesive is used for:
The adhesive should be applied evenly and at the recommended coverage rate. Applying too much adhesive can be just as problematic as applying too little, so always follow the instructions for the particular EPDM system you’re installing.
Bonding adhesive, often referred to as contact adhesive, is used where a strong contact bond is required, particularly around roof perimeters, upstands and other suitable details.
Roofer’s No.1 EPDM Bonding Adhesive is designed specifically for bonding EPDM and is ideal for use alongside the water-based deck adhesive as part of an EPDM installation.
Unlike water-based deck adhesive, bonding adhesive is applied to both the EPDM membrane and the substrate and allowed to flash off before the two surfaces are brought together.
Depending on the EPDM system and manufacturer’s instructions, typical applications include:
It is particularly useful where the membrane needs to be bonded onto vertical or non-porous surfaces.
| Water-Based Deck Adhesive | Bonding Adhesive | |
|---|---|---|
| Main purpose | Bonding the main EPDM roof area | Perimeters, upstands and details |
| Typical application | Suitable porous roof deck | EPDM and substrate |
| Application style | Wet bonding | Contact bonding |
| Best suited to | Large field areas | Edges, vertical surfaces and detailing |
| Positioning | More working time | Careful positioning required before contact |
The important point is that one adhesive isn’t necessarily better than the other. They are designed to perform different roles within an EPDM roofing system.
On a straightforward EPDM roof installed over a suitable OSB deck, you will commonly use water-based adhesive across the main roof area.
At the perimeter and areas such as upstands where water-based adhesive may not be appropriate, bonding adhesive is used instead.
This combination allows the membrane to be securely bonded across the roof while providing the stronger contact bond required at more challenging details.
Whichever adhesive you’re using, preparation matters.
The roof deck should be clean, dry and free from dust, dirt, oil and loose material before installation. The membrane should also be positioned correctly before adhesive application begins.
Allowing the EPDM membrane to relax before installation can make it easier to position and helps reduce wrinkles and tension during bonding.
Always check the installation instructions for your chosen EPDM system, particularly regarding suitable substrates, application temperatures, drying times and coverage rates.
Coverage varies depending on the adhesive, substrate and application method, so the manufacturer’s stated coverage should always be checked before ordering.
Remember to account separately for the main roof area and the perimeter/details, as these may require different adhesives.
It is also sensible to allow for a little additional material rather than calculating exactly to the last square metre.
One of the most common mistakes when installing an EPDM roof is assuming that a single adhesive should be used everywhere.
A better approach is to consider where the membrane is being bonded and what substrate it’s being bonded to.
For many typical installations:
Main suitable timber roof deck → Water-Based Deck Adhesive
Perimeters, upstands and appropriate details → EPDM Bonding Adhesive
Using each adhesive for the job it was designed to do helps achieve a secure, professional EPDM installation.
The Roof Store stocks EPDM membranes alongside water-based deck adhesives, bonding adhesives, primers, tapes, sealants and installation tools, making it easy to source the components required for your roofing project in one place.
Always follow the installation guidance for the specific EPDM membrane and adhesive system you’re using, as requirements can vary between manufacturers and products.
