{"product_id":"torch-on-felt-roofing-system-cap-sheet-underlay","title":"Torch-On Felt Roofing System – Mineral Cap Sheet \u0026amp; Underlay, Rolls \u0026amp; Trade Pallets","description":"\u003cp\u003eBuilt-up felt is still the most widely specified flat roof covering in Britain, and for good reason: two bonded layers of SBS-modified bitumen give you a genuinely redundant waterproof system, where the cap sheet takes the weather and the underlay beneath it is a complete second line of defence. This is that two-layer system — the charcoal mineral cap sheet and the glass-fibre-cored underlay that goes under it — available by the roll or by the trade pallet.\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003eTwo-layer torch-applied system: glass-fibre-cored underlay plus SBS polyester-cored mineral cap sheet\u003c\/li\u003e\n\u003cli\u003eCharcoal slate mineral finish — the granules take the UV so the bitumen beneath doesn't\u003c\/li\u003e\n\u003cli\u003eComplies with BS 8217:2005 when installed as a multi-layer system\u003c\/li\u003e\n\u003cli\u003eBuy single rolls for one roof, or full pallets at trade quantity\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch3\u003eSpecification\u003c\/h3\u003e\n\u003ctable\u003e\n\u003ctr\u003e\n\u003cth\u003eCap sheet roll\u003c\/th\u003e\n\u003ctd\u003e8m x 1m, charcoal slate mineral finish\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth\u003eCap sheet core\u003c\/th\u003e\n\u003ctd\u003ePolyester, saturated and coated in SBS-modified bitumen\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth\u003eUnderlay roll\u003c\/th\u003e\n\u003ctd\u003e16m x 1m (16m²), light sand upper finish\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth\u003eUnderlay core\u003c\/th\u003e\n\u003ctd\u003eGlass fibre, saturated and coated in bitumen\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth\u003eStandard\u003c\/th\u003e\n\u003ctd\u003eBS 8217:2005 as part of a multi-layer system\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth\u003eExpected life\u003c\/th\u003e\n\u003ctd\u003eIn excess of 15 years, correctly installed and maintained\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth\u003ePallet quantities\u003c\/th\u003e\n\u003ctd\u003eCap sheet 25 rolls; underlay 30 rolls\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/table\u003e\n\u003ch3\u003eFrequently asked questions\u003c\/h3\u003e\n\u003cp\u003e\u003cstrong\u003eHow many rolls do I need?\u003c\/strong\u003e Work from your roof area, then add for laps — felt is lapped at both side and end joints, so usable coverage is meaningfully less than the nominal roll area. As a rough guide, one 16m² underlay roll and two 8m² cap sheet rolls cover a small single garage. Measure, add roughly 10–15%, and round up to whole rolls.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eDo I need both layers?\u003c\/strong\u003e Yes. The cap sheet is not a standalone covering — the BS 8217 compliance, and the redundancy that makes felt reliable, both depend on it being bonded over an underlay. A single layer is a false economy on a roof you want to forget about for fifteen years.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eWhat does installing it involve?\u003c\/strong\u003e Torch-on felt is bonded with a propane roofing torch, melting the bitumen backing as the roll is unrolled. It is a skilled, hot-works job with real fire risk — most insurers and many local authorities have specific requirements around hot works on roofs. If you are not experienced with a roofing torch, this is a job for a contractor, or choose a cold-applied system instead.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eHow does it compare with EPDM?\u003c\/strong\u003e Felt is the traditional built-up system: proven, repairable in patches, and installed hot. EPDM is a single-piece cold-applied rubber membrane with a longer typical service life and no hot works. Both are sound choices — felt often wins on familiarity and repairability, EPDM on longevity and DIY-friendliness.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eWhat goes underneath?\u003c\/strong\u003e A sound, dry, well-supported deck. On a warm roof build-up the insulation and vapour control layer go beneath, in that order from the deck up.\u003c\/p\u003e\n\u003cp\u003ePrefer a cold-applied system with no torch? See our \u003ca href=\"\/products\/1-2mm-epdm-rubber-roofing-membrane\"\u003e1.2mm EPDM rubber membrane\u003c\/a\u003e. Building a warm roof? Lay our \u003ca href=\"\/products\/polythene-vapour-control-layer-vcl-4m-x-25m\"\u003epolythene vapour control layer\u003c\/a\u003e and \u003ca href=\"\/products\/pir-insulation-board-foil-faced-2400-x-1200mm\"\u003ePIR insulation board\u003c\/a\u003e beneath it first.\u003c\/p\u003e","brand":"Rubber Roof UK","offers":[{"title":"Mineral Cap Sheet – 1 roll (8m x 1m)","offer_id":46002563940543,"sku":"RRUK-FELT-CAP-8X1","price":117.99,"currency_code":"GBP","in_stock":true},{"title":"Underlay – 1 roll (16m x 1m)","offer_id":46002563973311,"sku":"RRUK-FELT-UND-16X1","price":119.99,"currency_code":"GBP","in_stock":true},{"title":"Mineral Cap Sheet – pallet of 25 rolls","offer_id":46002564006079,"sku":"RRUK-FELT-CAP-PALLET25","price":2839.99,"currency_code":"GBP","in_stock":true},{"title":"Underlay – pallet of 30 rolls","offer_id":46002564038847,"sku":"RRUK-FELT-UND-PALLET30","price":3459.99,"currency_code":"GBP","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0598\/1804\/9727\/files\/torch-on-felt-roof-charcoal-mineral-garage.jpg?v=1786483352","url":"https:\/\/rubberroofuk.uk\/products\/torch-on-felt-roofing-system-cap-sheet-underlay","provider":"Rubber Roof UK","version":"1.0","type":"link"}