A detached double garage in Dalton-in-Furness had a failing felt flat roof that was leaking onto the vehicles stored below. Our GRP fibreglass roofing team stripped the old felt, replaced damaged decking, and installed a seamless fibreglass roof system with a 25-year guarantee — transforming a problem roof into a maintenance-free, watertight covering.
This detached double garage at a residential property in Dalton-in-Furness had a traditional three-layer built-up felt flat roof installed approximately 18 years earlier. The felt had deteriorated significantly — blistering across the central area where standing water collected due to inadequate falls, and cracking along the front edge where UV exposure was most intense. Two areas of felt had split completely, allowing rain to drip directly onto the car stored below. The garage owner had been using tarpaulins as a temporary measure but was now finding water pooling on the garage floor after every rain event. Inspection from above revealed that the 18mm chipboard decking beneath the felt had become soft and swollen where water had been penetrating through the blisters, creating a spongy surface that would not support a new covering without replacement. The roof measured approximately 28 square metres — a typical garage size ideally suited to a GRP fibreglass system.
We stripped all existing felt and the water-damaged chipboard decking, exposing the roof joists for inspection. The joists were in good condition — being a garage, the roof had adequate ventilation beneath that had prevented condensation damage. We installed new 18mm Sterling OSB3 boarding across the entire roof area, with tapered firring strips on top of the joists to create a consistent 1:60 fall from back to front. This improved fall ensures water drains positively towards the front gutter rather than pooling in the centre as before. The GRP fibreglass system was then applied: resin primer on all OSB surfaces, pre-formed GRP edge trims bedded in resin along all four edges and at the gutter line, 450g/m² chopped strand mat laminated into catalysed polyester resin across the entire roof area with 75mm overlaps at all trim junctions, a second resin consolidation coat, and finally a dark grey topcoat providing UV protection and a clean, professional finish. The entire system was completed in a single day of laminating work.
The garage now has a completely seamless, jointless GRP flat roof with zero risk of leaking. The improved falls mean water drains cleanly to the front gutter within minutes of rain stopping — no more standing water. The dark grey finish gives the garage a smart, professional appearance that complements the house. The homeowner was particularly impressed by the speed of installation — the entire project from strip to completion took just 3 days including the decking replacement. We provided a 25-year guarantee on the GRP roofing system.
The GRP (Glass Reinforced Polyester) roofing system consists of a polyester resin matrix reinforced with chopped strand glass fibre mat. When cured, this creates a rigid, seamless, completely waterproof shell that is impervious to water, UV radiation, and temperature extremes. The system is applied in liquid form and cures in place, meaning it conforms perfectly to any roof shape with zero joints, laps, or seams. This is why GRP is considered the gold standard for flat roofs — there are simply no weak points where water can penetrate.
OSB3 (Oriented Strand Board, moisture-resistant grade) is the recommended substrate for GRP roofing systems. The oriented strand construction provides excellent dimensional stability and screw-holding properties, while the phenolic resin binder provides moisture resistance if any water ever reaches the board. The 18mm thickness provides adequate stiffness across the standard 400mm joist centres on this garage.
Factory-manufactured GRP edge trims provide clean, professional terminations at all roof edges and gutter lines. These trims are bedded in resin before the main laminate is applied, with the glass mat overlapping onto the trim to create a monolithic connection. The trims incorporate a drip detail that directs water cleanly into the gutter or away from the fascia board.
The dark grey topcoat contains UV stabilisers that protect the underlying resin from solar degradation, extending the system's life significantly. The topcoat also contains a wax additive that rises to the surface during curing, creating a fully cured, tack-free finish that resists dirt accumulation and is easy to clean.
If your garage roof is leaking, blistering, or coming to the end of its life, our GRP fibreglass roofing team can provide a permanent, maintenance-free solution. We serve Dalton-in-Furness, Barrow, Askam and all surrounding areas. Contact us today for a free survey and quotation.
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