{"product_id":"breathable-roofing-membrane-125gsm-roof-wall-underlay","title":"Breathable Roofing Membrane – 125gsm Roof \u0026amp; Wall Underlay, 50m Rolls \u0026amp; Taped Kits","description":"\u003cp\u003eUnder every tiled or slated roof there is a membrane doing quiet, unglamorous work: shedding any water that gets past the covering, while still letting moisture from inside the building escape rather than condensing in the roof space. Get that layer wrong and you find out years later, in the form of damp timbers. This is a 125gsm breathable roof and wall underlay, supplied as a 50m roll or as a complete taped kit.\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e125gsm breathable membrane for pitched roofs and insulated walls\u003c\/li\u003e\n\u003cli\u003eWater resistant from outside, vapour permeable from inside — no separate ventilation strategy needed for the membrane itself\u003c\/li\u003e\n\u003cli\u003eTwo roll widths: 1m x 50m (50m²) and 1.5m x 50m (75m²)\u003c\/li\u003e\n\u003cli\u003eComplete kit option adds the lap tapes needed to seal it properly\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch3\u003eSpecification\u003c\/h3\u003e\n\u003ctable\u003e\n\u003ctr\u003e\n\u003cth\u003eWeight\u003c\/th\u003e\n\u003ctd\u003e125gsm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth\u003eRoll sizes\u003c\/th\u003e\n\u003ctd\u003e1m x 50m (50m²) and 1.5m x 50m (75m²)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth\u003eColour\u003c\/th\u003e\n\u003ctd\u003eMatt black\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth\u003ePerformance\u003c\/th\u003e\n\u003ctd\u003eWater resistant and vapour permeable\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth\u003eApplications\u003c\/th\u003e\n\u003ctd\u003ePitched cold roofs, pitched warm roofs, insulated walls\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth\u003eComplete kit contains\u003c\/th\u003e\n\u003ctd\u003e1 membrane roll, 2 rolls single-sided lap tape, 1 roll double-sided lap tape\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/table\u003e\n\u003ch3\u003eFrequently asked questions\u003c\/h3\u003e\n\u003cp\u003e\u003cstrong\u003eRoll or complete kit?\u003c\/strong\u003e The membrane only performs as a continuous layer, which means the laps have to be sealed. If you already have lap tape, buy the roll. If you don't, the kit works out simpler than sourcing tapes separately — it includes both the single-sided and double-sided tapes the job needs.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eWhich width?\u003c\/strong\u003e 1.5m covers ground faster and leaves fewer horizontal laps, so it suits larger, simpler roof planes. 1m is easier to handle single-handed and wastes less on cut-up roofs with lots of hips, valleys and dormers.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eHow much do I need?\u003c\/strong\u003e Work from the roof slope area, not the footprint, and allow for horizontal laps between courses plus generous overlaps at ridges, hips and valleys. Round up to whole rolls.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eHow is it fixed?\u003c\/strong\u003e Laid horizontally starting at the eaves and working up, so each course laps over the one below, then held by the tile battens fixed through it into the rafters. Keep it taut but with a slight natural drape between rafters so any water that gets through runs down the membrane rather than pooling on it.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eCan I use it on a flat roof?\u003c\/strong\u003e No. This is a pitched roof and wall underlay. A flat roof needs a fully waterproof covering — see our EPDM, felt and GRP systems instead.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eIs this the same as a vapour control layer?\u003c\/strong\u003e No, and they do opposite jobs. This is designed to let vapour out through the roof. A vapour control layer is designed to stop vapour getting in, and sits on the warm side of the insulation.\u003c\/p\u003e\n\u003cp\u003eBuilding a warm flat roof instead? You want 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. Covering a flat roof? See our \u003ca href=\"\/products\/1-2mm-epdm-rubber-roofing-membrane\"\u003e1.2mm EPDM membrane\u003c\/a\u003e or \u003ca href=\"\/products\/torch-on-felt-roofing-system-cap-sheet-underlay\"\u003etorch-on felt system\u003c\/a\u003e.\u003c\/p\u003e","brand":"Rubber Roof UK","offers":[{"title":"1m x 50m roll (50m²)","offer_id":46002582847679,"sku":"RRUK-BREATHER-1X50","price":87.99,"currency_code":"GBP","in_stock":true},{"title":"1.5m x 50m roll (75m²)","offer_id":46002582880447,"sku":"RRUK-BREATHER-15X50","price":123.99,"currency_code":"GBP","in_stock":true},{"title":"1m x 50m complete kit with lap tapes","offer_id":46002582913215,"sku":"RRUK-BREATHER-1X50-KIT","price":179.99,"currency_code":"GBP","in_stock":true},{"title":"1.5m x 50m complete kit with lap tapes","offer_id":46002582945983,"sku":"RRUK-BREATHER-15X50-KIT","price":213.99,"currency_code":"GBP","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0598\/1804\/9727\/files\/breathable-roofing-membrane-pitched-roof-battens.jpg?v=1786484369","url":"https:\/\/rubberroofuk.uk\/products\/breathable-roofing-membrane-125gsm-roof-wall-underlay","provider":"Rubber Roof UK","version":"1.0","type":"link"}