EPDM is a synthetic rubber membrane that arrives as one continuous sheet and is bonded to the deck. On most domestic flat roofs up to around 40 square metres it can be laid with no seams at all across the field of the roof, which removes the single most common failure point in flat roofing.
Single sheet rubber membrane with no field seams. Our default recommendation for most domestic flat roofs.
Why it is our usual first recommendation
Seams fail. Felt has them at every lap, GRP has joints at every board edge if the install is rushed, and single ply has welds. A one piece EPDM sheet has none across the main area, so the only vulnerable points are the perimeter details and the penetrations, which are exactly the places we can control.
It is also cold applied. No torch, no hot bitumen, no naked flame near your fascia, soffit or a timber garage. On attached garages and dormers that matters more than people realise.
Garage roofs, single storey rear extensions, dormer tops and cheeks, porches, bay tops and garden rooms. Anywhere the roof is modest in size, has a straightforward shape and needs to last without maintenance.
Copes well with building movement because the rubber stretches rather than cracks
Unaffected by UV in a way that bitumen felt is not
Repairable: a damaged area can be patched and welded into the existing sheet
Available in trims and edge details that look tidy from ground level
Where it is not the right answer
EPDM is not the choice for a roof that will be walked on regularly or used as a terrace, where a reinforced system or a proper walk on finish is needed.
It also gains nothing on a very large commercial roof where a mechanically fixed single ply system with welded seams is designed for the span. And if the deck below is wet or rotten, no membrane will save it. The deck gets replaced first or the job is not worth doing.
What a proper EPDM installation includes
The membrane is only part of it. A good EPDM roof stands or falls on the deck preparation, the falls, the trims and the outlet detail.
Deck inspected and any soft boards replaced, not covered
Falls checked so water reaches the outlet rather than ponding
Insulation upgraded to current building regulations on a full replacement
Bonded adhesive across the field, contact adhesive at upstands
Preformed corners rather than folded and hoped for
Aluminium or preformed edge trims and a proper drip into the gutter
How long does an EPDM roof last?
A properly installed EPDM roof is typically good for 30 years or more. Failures we are called to nearly always come from poor detailing at the edges rather than the membrane itself.
Can EPDM be laid over the existing felt?
Sometimes, but only if the felt is dry, well bonded and the deck below is sound. If there is any moisture trapped underneath it will not be doing you a favour, and we would rather strip it.
Is EPDM cheaper than GRP?
Usually slightly cheaper per square metre, and it is faster to install because there is no cure time. GRP wins where you want a hard, walkable finish.
Can it be laid in cold weather?
Yes, within reason. It is cold applied so there is no hot works, but adhesives have minimum temperatures and the deck must be dry, so we will not lay in rain or hard frost.
Does an EPDM roof need maintenance?
Very little. Keep the outlet clear and check the trims after a bad storm. That is genuinely most of it.
We check the deck by walking and probing it, look at the falls and inspect the outlet before quoting.
Quote with the system named
Membrane thickness, insulation spec and trim type all written down, so you can compare quotes on like for like.
Strip and repair the deck
Old covering off, soft boards replaced, deck screwed down firm and clean.
Insulation where required, then the membrane relaxed, bonded and dressed into every upstand and trim.
Corners, outlets and edges finished, then the roof flushed with water so you can see it drains.
Evans Roofing & Maintenance Ltd, Witney, Oxfordshire. Call 07960 482233 for a free written quote.