Rubber Roof Cost: EPDM Price Factors Explained

EPDM arrives as one sheet, so a plain rectangular garage, dormer or extension can often be covered with no seams in the field of the roof. That is fast to install and is why EPDM suits simple decks well. There is also no on-roof curing, so weather windows are less of a concern.

Each corner, step, upstand or pipe needs detailing with matching accessories. A roof with many of these takes longer, and on very complex shapes a system formed wet on the deck may be the better choice. Our EPDM versus GRP comparison explains how the shape of the roof points towards one system or the other.

A rubber membrane is only as good as the surface it is bonded to. When the old covering comes off, the timber deck is checked. Sound boards are kept; wet or rotten ones are replaced. That can change the cost noticeably, so a good quote explains how deck repairs will be priced if they are found.

Laying EPDM over old felt is not recommended. Stripping back allows the deck to be inspected and stops damp being sealed in under the new roof.

Replacing the covering is the best moment to upgrade to a warm roof, with insulation laid on the deck under the membrane. It adds material and labour cost, but reduces condensation risk and can make the room below more comfortable. Extra thickness raises the roof edge, which affects trims, fascias and any door or window thresholds that meet the roof.

EPDM roofs are finished with edge trims and kerbs, and the membrane is turned up walls and other abutments. The outlet or gutter detail needs care so water leaves the roof cleanly. Where a wall abutment also needs a flashing above the upstand, that may be leadwork listed separately.

These details are where flat roofs most often fail, so it is worth checking each quote describes them rather than assuming they are included.

For a fair comparison, make sure each quote covers stripping and waste, deck inspection and repair terms, insulation if wanted, trims and upstands, outlets and access. A cheaper figure that leaves out the deck or the edges may cost more by the time the job is finished.

If you are weighing EPDM against other systems on a whole flat roof replacement, our flat roof replacement cost page covers the wider picture across materials, and our EPDM rubber roofing page explains how we fit it.