How an EPDM Rubber Roof Is Installed
EPDM (ethylene propylene diene monomer) comes in large rolls, so on most garage and extension roofs the membrane can be cut from a single sheet sized to the whole roof. The deck beneath must be sound, smooth and dry, so we strip the old covering, replace soft or damaged boards and make sure there is enough fall to shed water towards the gutter or outlet.
The membrane is laid out and left to relax, then folded back so adhesive can be applied. Systems typically use a water-based adhesive across the main area and a contact adhesive around the perimeter and on upstands. Each half is bonded and rolled to push out trapped air.
At walls, the membrane is turned up to form an upstand and finished under a flashing or termination detail so water cannot get behind it. Edge trims form the drip into the gutter and the raised kerbs along open sides, while corners, pipes and outlets are sealed with pre-formed pieces and tapes from the same system.
EPDM Compared With GRP and Felt
Rubber suits many flat roofs, but not every one. These are the main points we talk through with customers.
Where EPDM has the advantage
- Few joints: smaller roofs can usually be covered in one sheet, whereas felt is laid in overlapping layers.
- Flexibility: rubber tolerates some movement and temperature change, while rigid GRP can crack if the deck moves.
- No hot works: it is bonded with adhesive, so there is no naked flame, unlike torch-on felt.
- Simpler weather window: it still needs a dry deck and suitable temperatures for the adhesive, but there is no resin to cure as there is with GRP.
Where GRP or felt may suit better
- Foot traffic: rubber can be punctured by sharp objects, so roofs that are walked on regularly may need protective walkway pads or a harder-wearing system.
- Complex details: roofs with many pipes, rooflights and corners take careful detailing in EPDM, whereas GRP is laminated around details in one layer.
- Appearance: EPDM has a plain black finish, while GRP topcoats and mineral-surfaced felt offer different looks.
- Compatibility: bitumen-based products should generally not be used on EPDM, so later repairs need rubber-compatible materials.
Read more on our GRP fibreglass roofing and felt roofing pages.
