GRP fibreglass flat roof · 2025
Detached garage fibreglass roof
A double garage roof had been patched with three different felts and still leaked onto the owner’s classic car. We stripped it all off, re-decked the soft boards, and hand-laid a seamless GRP fibreglass roof with a moulded drip trim.
Job sheet
- Location
- Dronfield, S18
- Scope
- Strip & GRP re-cover
- Materials
- Hand-laid GRP fibreglass
- Duration
- 2 days
- Deck area
- 38 m²
- Layers
- 3 → 1
- Guarantee
- 20 yr
Before
Layers of blistered, patched felt with an open split along the seam, dripping onto the car below.
After
A single seamless GRP fibreglass roof in slate grey with moulded trims, walk-on tough and completely watertight.
What we found once the scaffold was up
Three layers of felt deep, which is three chances for water to run sideways before it drops. Tracing the leak from underneath was never going to work, so the whole build-up came off.
How it was built back
Four soft boards underneath, re-decked in 18mm OSB3. The GRP then went on wet-on-wet in a single session so the laminate cures as one sheet rather than as layers that can delaminate. Dronfield sits high and exposed, and wind gets under a loose edge in seconds, so the drip trims are bonded in beneath the laminate instead of screwed on top of it.