Stonesfield slate roof – How to install TLX batsafe?

Stonesfield slate roof – How to install TLX batsafe?

We recently received an enquiry about how to install TLX Batsafe, should it be draped or pulled taught and counter battened, which posed the questions which is the best option?

The local ecologist specified TLX Batsafe for a stonesfield slate roof, which was in the midst of being re-roofed for the client when bats were found.  

The question arose when the roofing contractor, ecologist and architect each had a different opinion on how TLX Batsafe should be installed. 

The debate was - whether the membrane should be pulled “tight" across the roof, or if it should “sag" between the rafters, and if it should "sag", by how much (i.e. whether the underside of the TLX Batsafe can touch the top of the rigid insulation). The other area of concern was water run-off from the membrane.

tlx batsafe stonesfield slate reroof projectThe answer:

TLX Batsafe is installed in the same way as a standard breather membrane, so it is either installed draped over the rafters with the tile batten fixed directly over the top of the TLX Batsafe or it is pulled tight over the rafters, in which case a counter batten will be needed above the TLX Batsafe before the tiling battens are fitted, raising the roof height. 

If draping the membrane, it should drape by 10-15mm (In accordance with BS5534 Code of practice for slating and tiling) into the rafter void to create an adequate channel for ventilation above the TLX Batsafe and to provide a route for any water that gets behind the tiles, to run off to the guttering. If the membrane comes into contact with the insulation, this will not cause a condensation risk, but it may reduce the thermal performance of the roof section as the unventilated air gap between the TLX Batsafe and rigid insulation is contributing to the overall U value. When draping the TLX Batsafe we would recommend that a 25mm void is maintained at top of the rafter to allow for both the 10-15mm membrane drape and an unventilated air gap.

tlx batsafe technical helpline