Cavity Trays Ltd, the longest-established specialist in its field now has flashing options available across its range of approved cavity trays. There are now four flashing materials from which the client may select: Lead, Synthetic, Copper and Aluminium. This extends the clients options pending the adjacent roof type and finish, location and aesthetics.
But, Cavity Trays has announced it is not reducing the dimensions of its flashings, despite alternative manufacturers offering trays with flashings that do not match the length of the tray.
‘Our approved trays are accompanied with a performance undertaking’ commented a company spokesperson, ‘and our Type X tray for gable abutments has high-exposure rating. Adequate flashing laps can be critical especially in locations of variable exposure – a view promoted by the LSA. We have experimented with varying flashing dimensions but having identified the adequacy of our current flashing dimensions in relation to tray size and flashing interfacing, and do not wish to reduce the intended cover margins.
Exposure tests have highlighted the extent by which wind-driven rain can challenge the leading edge of stepped flashings. Penetration behind and beyond the leading stepping edge must be anticipated.
By ensuring the relationship between trays (and thus between flashings also) extends sufficiently to arrest wind-driven rain, dampness can be prevented from permeating inwardly below the abutting roof-line. But there are accompanying considerations such as the tail of our flashing being shaped to permit transitory drainage and the flashing/tray union being bonded within a bosem jaw.’ Further information about the Type X trays can be found in: Gable Abutments, volume 21. Available upon request.