Flat Roofing for Conservatories, Dormers and Lean-To Roofs
Conservatories, dormers and lean-to roofs each throw up their own flat-roofing problems — low pitches, awkward junctions with the house wall, and old polycarbonate or glass that makes the room too hot in summer and too cold in winter. Replacing them with a solid, insulated flat roof fixes all three.
In short
A tired polycarbonate conservatory roof or a leaking lean-to can be replaced with a warm, insulated EPDM or GRP flat roof — usually in a day or two, often without planning permission. It stops the leaks, makes the room usable all year, and looks like part of the house rather than an afterthought.
Conservatory flat roofs
Many older conservatories have a low-pitch polycarbonate or glass roof that leaks at the bars, roars in heavy rain and makes the room unbearable in July and freezing in January. Replacing it with a solid, insulated flat roof — a warm-roof build in EPDM rubber or GRP, with a plastered ceiling inside — turns it into a proper room. The existing frames and glazed walls usually stay; it is the roof that changes. A lightweight tiled conversion is the other option where the pitch allows, but a flat roof is simpler, cheaper and works on the shallowest pitches.
Dormer roofs
The small flat roof on top of a dormer window is one of the most common leak points on a house. The covering is small and old, the upstands where it meets the tiled roof and the dormer cheeks are fiddly, and a lot of them were felted decades ago and never touched since. Re-covering a dormer roof in EPDM — a single sheet dressed up the cheeks and into the abutment — is a quick job that ends the leak for good. Typically £600 to £1,200.
Lean-to and outrigger roofs
A lean-to roof over a utility room, a rear addition or an old scullery slopes gently away from the house and tucks under the main roof or against the wall. The weak points are the top junction — where a bad flashing lets water track behind — and the very low pitch, which felt struggles with. A warm-roof EPDM or GRP covering with a proper lead or GRP upstand into the wall handles the low pitch and seals the junction that was leaking.
Which covering for which job
EPDM rubber suits almost all of these: seamless, flexible, fine on very low pitches, and quick to fit. GRP fibreglass is worth the extra where the roof will be walked on or where you want a hard, coloured finish — a balcony above a room, for instance. Both are built as warm roofs with insulation over the deck, so the room below stays comfortable and there is no condensation on the underside.
Frequently Asked Questions
Do I need planning permission to replace a conservatory roof with a flat roof?
Usually not — a like-for-like roof replacement on an existing conservatory is normally permitted development. Building regulations may apply to the new roof structure and insulation. We confirm both before starting.
Will a solid flat roof make my conservatory warmer?
Yes, considerably. A warm-roof build with insulation over the deck stops the heat loss through the old polycarbonate in winter and the solar gain in summer, so the room becomes usable all year.
How much does it cost to replace a conservatory roof with a flat roof?
For a typical lean-to or Edwardian conservatory, expect roughly £2,500 to £5,000 depending on size, the covering and whether the ceiling is plastered inside. We give a fixed written price after a survey.
Why does my dormer roof keep leaking?
Almost always the upstands — where the small flat roof meets the tiled slope above and the dormer cheeks at the sides. Old felt cracks at those folds. A one-piece EPDM re-cover dressed up the cheeks and into the abutment fixes it.
Related Reading
Flat roof replacement cost: felt vs EPDM vs GRP
Read moreUK costs for each covering.
How much does rubber roofing cost in the UK?
Read moreEPDM rubber roof prices by roof type.
EPDM vs fibreglass vs felt flat roofing
Read moreComparing the three flat roof coverings.
Warm roof vs cold roof explained
Read moreWhere the insulation sits and why it matters.
Leaking Conservatory, Dormer or Lean-To?
We replace conservatory, dormer and lean-to roofs with warm, insulated EPDM and GRP flat roofs across the South Wales valleys — usually in a day or two. Free survey.