We replace and repair flat roofs throughout Dorset: rear extensions, garages, dormer cheeks and tops, porches, and the balcony and terrace decks so common on coastal properties.
Why Dorset flat roofs fail
Older felt roofs on 1960s and 70s extensions have usually had thirty years more life out of them than they were ever designed for. The bitumen's oxidised, the chippings have migrated, and the first hard frost after a wet autumn opens up a split.
On coastal properties there's a second factor: wind uplift. A flat roof with poorly fixed perimeter trim on an exposed elevation at Portland or Swanage takes a battering a sheltered inland roof never sees, and the edge detail is where it starts to lift.
Which system suits which job
EPDM rubber membrane
A single sheet with very few joints, laid in one piece on most domestic roofs. It's flexible in cold weather, unaffected by UV, and a great choice for extensions and garages where the roof isn't walked on regularly.
GRP fibreglass
A seamless, hard-wearing finish that suits balconies, terraces and any deck that gets foot traffic. It needs dry, settled conditions to lay properly and a stable deck underneath, so the groundwork matters just as much as the topcoat.
Torch-on felt and single-ply
Modern high-performance built-up felt is still a sound, economical option on larger areas, and single-ply membranes work well where you want a lightweight system with mechanically fixed detailing.
The details that decide how long it lasts
- A genuine fall to the outlet — a level deck is a pond waiting to happen
- Upstands taken high enough at abutments and properly flashed or chased in
- Outlets and rainwater connections sized for the area they drain
- Perimeter trim mechanically fixed, particularly on exposed coastal elevations
- Warm-roof insulation with the vapour control layer on the correct side
Warm roof upgrades
Where an old cold-deck roof is being replaced, we'll usually recommend rebuilding it as a warm roof: insulation above the deck, membrane over the top. It removes the condensation risk that rots joists from the inside, and it makes the room below noticeably more comfortable — well worth having on any extension you actually live in.
