EPDM or felt: which flat roof is the right one?

Why the felt gives up

Torch-on felt and older asphalt shrink in the sun, split at the edges, and hold a pond where the outlet has dropped. Water finds the hairline crack above the kitchen, runs along the deck, and shows up on the ceiling somewhere else. Another coat of felt over the top can buy a season. It does not fix a soft board.

EPDM is a rubber sheet. On a straightforward extension or garage it goes down in one piece, so there is no joint in the middle of the roof to open up next summer. It moves with the building instead of cracking when the timber does.

When felt, rubber, or a liquid is the honest choice

If the deck is sound and the build-up is not already too high at the door, a clean overlay is sometimes fair. If the boards are rotten, we strip back and replace them, then lay the rubber. Burying the old felt under a new membrane is how the last roof failed.

A liquid coating earns its place on an awkward shape: pipes, a balcony, a lantern kerb that a single sheet cannot hug. GRP fibreglass is another system people get quoted. For most home extensions in Hornchurch we would rather lay EPDM. We will say so on site rather than sell the product that happens to be on the van.

Lead still does the junction with the house wall, the chimney and the bay. Rubber on the flat and lead at the wall is the detail that keeps the ceiling dry. One without the other just moves the leak.

How to choose without guessing

Send a photo of the roof and the ceiling stain. If we can see the felt has split but the deck looks firm, we will say that. If we need to walk it, the look is free and the quote splits the deck, the membrane and the trims so you can see what you are paying for.

The job we are asked for most is exactly this: take the failed felt off a Hornchurch extension and put rubber down properly, outlets and all.