This terraced property near Cockermouth's riverside had experienced internal water damage during a severe rainfall event. While the main pitched roof was unaffected, the rear extension flat roof had allowed water to penetrate through deteriorated upstand details where the felt met the back wall of the house. The felt surface itself was still largely intact, but our inspection revealed that the mineral wool insulation beneath had become completely saturated. Wet insulation loses virtually all its thermal value and creates a persistent moisture source that promotes timber decay — it had to be replaced entirely.
We stripped the existing felt and removed all the waterlogged mineral wool insulation. The timber deck beneath was still sound — dried out and structurally solid after the felt was removed. We installed new 80mm Kingspan PIR insulation (which doesn't absorb water like mineral wool) with tapered sections directing water toward the gutter. A vapour barrier was added, and we then applied a two-layer SBS-modified bitumen torch-on felt system — a significant upgrade from the original single-layer felt. The abutment to the house wall received a new code-5 lead flashing properly dressed into the masonry.
The property now has a flat roof that's dramatically more resilient than the original — closed-cell PIR insulation that won't absorb water even if moisture does penetrate, properly detailed upstands with lead flashings, and a two-layer torch-on membrane far tougher than single-layer felt. The customer has peace of mind knowing that even in Cockermouth's extreme rainfall conditions, the extension is properly protected. Visit our flat roof repairs page for more information on similar projects.
The two-layer SBS-modified bitumen system uses a base sheet and cap sheet applied using controlled heat from a gas torch. The SBS (styrene-butadiene-styrene) modifier gives the bitumen dramatically improved flexibility, tear resistance, and lifespan compared to traditional oxidised bitumen felt. The two-layer system provides redundancy — even if the cap sheet is damaged, the base sheet maintains waterproof integrity beneath. Expected lifespan is 20 to 25 years with minimal maintenance.
Kingspan PIR insulation uses a closed-cell foam structure that physically cannot absorb water — unlike the mineral wool it replaced, which acts like a sponge when exposed to moisture. For a property in Cockermouth's flood-risk area, this is a critical specification choice. Even if water were to reach the insulation through some future event, it would dry out without losing its thermal properties or promoting timber decay. This resilience-focused material choice is part of our commitment to delivering roofing solutions appropriate to each property's specific risk profile.
If your Cockermouth property needs flat roof repairs — whether it's flood damage restoration, a failing felt roof, or a complete replacement — contact Mr Roofer for a free assessment. We install GRP fibreglass, EPDM rubber, and torch-on felt systems. Visit our flat roof repairs page or call your local Cockermouth roofing team today.
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