Roofing felt adhesive is useful where the felt system specifies bonded laps or bonded layers, but it does not automatically replace felt nails. The correct fixing method depends on the roofing felt and roof build-up.
Black Jack 904 is made for compatible bituminous roofing felt
Everbuild Black Jack 904 bonds compatible roofing felt to timber, concrete, metal and existing felt. Sika also specifies it for sealing felt laps.
On timber multi-layer roofs, Sika still requires the first layer to be nailed
For its 904 adhesive system, Sika states that the first felt layer on a timber roof is mechanically nailed; second and third layers may then be bonded. That is why “just glue it” is not a safe universal installation rule.
Adhesive is particularly useful at compatible laps
Sika specifies liberal adhesive beneath laps and good compaction. In its own 904 system it gives minimum laps of 75mm at edges and 150mm at roll ends. If the roofing felt manufacturer specifies a different lap, follow the felt system being installed.
Coverage is approximately 1.3–1.6m² per litre
That is Sika's current stated yield when 904 is used as roof felt adhesive. The product is available from Wern-Wood in 1L, 2.5L and 5L tins.
Adhesive does not rescue a bad roof deck
The substrate still needs to be stable and clean. Repair damaged decking, loose felt and significant defects before bonding over them.
For the complete fitting sequence, read How to Felt a Shed Roof, or shop the Roofing Felt & Shed Felt range.
