Flat roofing
Flat roofing in EPDM, GRP and felt
New and replacement flat roofs for extensions, garages, dormers and commercial buildings, insulated to current standards and finished properly at every edge.
Systems
Choosing a flat roof system
We fit all three. Which one suits depends on the size of the roof, whether it'll be walked on, and the budget.
| System | What it is | Typical lifespan | Good to know |
|---|---|---|---|
| EPDM rubber | A single sheet of synthetic rubber, bonded to the deck | 20 to 30 years or more | Few or no joints, and stays flexible in cold weather |
| GRP fibreglass | Resin and glass matting laid on site, finished with a topcoat | 20 to 30 years or more | Seamless and hard-wearing, so it copes with foot traffic |
| Torch-on felt | Layers of modified bitumen felt, heat-welded in place | 15 to 20 years | Traditional and economical, with a mineral finish against UV |
Lifespans depend on how well the roof is laid and looked after.
Build-up
What goes into a warm flat roof
Most replacement flat roofs are built as a warm roof, with the insulation above the deck so the timbers stay warm and dry.
- Deck
- OSB3 or plywood boards over the joists
- Vapour control
- Stops moisture from the room reaching the insulation
- Insulation
- Rigid PIR boards to the thickness required
- Waterproofing
- EPDM, GRP or felt
- Upstands
- Turned up the walls and dressed under a lead cover flashing
- Edges
- Trims, drips, outlets and gutters to get the water off cleanly
Warning signs
When a flat roof needs attention
Standing water
Puddles still there two days after rain mean the roof has sagged or the outlets are blocked.
Splits, blisters and cracks
Felt that has blistered or split, and cracked GRP, let water under the surface.
Damp patches inside
Stains on the ceiling below are often the first sign, and the leak may be some way from the stain.
Moss and plants
Anything growing on a flat roof is holding water against it and working its roots into the surface.
Lifting edges
Trims and upstands coming away let wind-driven rain straight in.
Process
Replacing a flat roof
Most domestic flat roofs are stripped and replaced in a few days, weather allowing.
- Step 1
Strip
The old covering comes off and the deck is checked.
- Step 2
Deck
Soft or rotten boards are replaced and any falls corrected.
- Step 3
Insulate
Vapour control and PIR insulation, to current standards where required.
- Step 4
Waterproof
EPDM, GRP or felt laid and dressed up the walls.
- Step 5
Finish
Trims, lead cover flashings, outlets and gutters, then a full clean-up.
Questions
Flat roof questions
Do I need Building Regulations for a new flat roof?
If most of the roof is being replaced, the insulation usually has to be brought up to current standards and Building Control needs to know. We'll tell you whether yours is affected when we survey it.
Can you repair it rather than replace it?
Often, yes. A split or a failed edge can usually be repaired. If the deck underneath has gone soft, or the roof is failing in several places, replacement is better value.
Can a flat roof be walked on?
GRP copes best with foot traffic. For a roof that will be used regularly, such as a balcony, it needs to be designed for it from the start.
Flat roof letting water in?
Book a survey and we'll tell you whether it's a repair or a replacement.