CPD Specifier May 2015 issue May 2014 | Page 29

Repair, Refurb, Retrofit Damp Level Thresholds? Isolate the problem In excess of 70% of damp problems associated with level thresholds originate through a failure to correctly interface converging protective elements. A recent investigation suggests the three most common failures occur for the following reasons: 1. Incorrect integration of the vertical closing arrangement at threshold level. 2. Failure to adequately incorporate isolation measures where the floor construction unites with inner and outer masonry skins. 3. Where the Type LTT meets the reveal masonry either side of the opening it continues upwardly and around both faces of the reveal, wrapping the masonry skin and extending into the actual cavity. Any reveal cavicloser simply projects downwardly between the protective wraps at each end of the tray. The standard horizontal DPC in both skins can safely terminate at any course level within each protective wrap - regardless of the threshold level. Insufficient oversite membrane is available to turn up all wall/ reveal faces after being stretched around the 90° internal skin corner projecting into the room. Consequently the membrane is usually cut to accommodate the projection and a weakness results adjacent to the reveal face. The Type LTT by Cavity Trays of Yeovil promotes a standardised route to damp-free level thresholds. By isolating the masonry most susceptible to damp transference, the Type LTT permits abutting flooring, abutting insulation, horizontal DPC’s and oversite membranes to safely integrate. The flooring arrangement may continue over an inside skin and converge with an exterior skin that itself is isolated from dampness at the point of convergence. The Type LTT requires no further work once fitted to the inside skin and is undetectable when works are complete. When fitted to the outside skin, the Type LTT may be trimmed back externally to suit the frame position upon completion of work, so it is not readily visible. When used with Caviclosers from the range offered by Cavity Trays Ltd, the specifier benefits assured compatibility and an accompanying performance warranty. The Type LTT (Level Threshold Tray) by Cavity Trays of Yeovil offers a standardised approach designed to overcome such inadequancies. The Type LTT is a ready-shaped DPC specifically designed for use on both inner and outer masonry skins at threshold level. The Type LTT acts as an isolation DPC ‘glove’ enveloping and covering the top and the sides of the threshold masonry. Once in place, flooring arrangements can interface with the skins at threshold level without danger of wet transference. CAVITY TRAYS TEL: 01935 474769 WWW.CAVITYTRAYS.CO.UK READER ENQUIRY NO: 39 29 Page 29.indd 1 10/04/2014 10:51:57