Level Threshold Openings – An Easy Method of Ensuring Damp Protection Integrity
The Type LTT is a Level Threshold Tray manufactured by Cavity Trays of Yeovil.
It provides a uniform standardised construction arrangement that removes risk.
By isolating one of the area’s most susceptible to damp transference, the Type LTT permits abutting flooring, abutting insulation and DPC’s / membranes to integrate with an inside skin and converge with an exterior skin that itself is isolated from dampness at the point of convergence.
Flooring terminating at an exterior level-threshold door opening is obliged to provide a continuous structural relationship up to the opening frame/sill.
Given that the meeting point is commonly below the DPC level present within the exterior wall skins, the question arises of how connection can be made and maintained without dampness permeating inwardly? Additionally, the reveal vertical DPC’s (whether provided traditionally or in the form of a reveal closer) must come together at floor level in a manner that converges these protective elements in a waterproof manner.
Level thresholds that fail to secure the above qualities will not provide damp-free service.
The function of the Type LTT is to act as a DPC glove, enveloping the top and sides of the threshold structural masonry. A Type LTT can be bedded on both inner and outer masonry skins, regardless of whether those skins terminate at the same level. (The inner skin is often at a lower level to accommodate the depth of the flooring arrangement). Because both skins are effectively enveloped and protected, the floor can connect, bear and interface with either skin without fear of dampness via the connection.
Where the Type LTT meets the reveal masonry either side of the structural opening, it continues upwardly and additionally wraps around both faces of the reveal skin, extending into the actual cavity. So doing permits the reveal to be insulated and closed using an approved Cavicloser wherein the bottom of the Cavicloser is notched to safely integrate with the upstands of the Level Threshold Tray.
The horizontal DPC’s in the inner and outer skins of the exterior wall are usually at a higher level than that of the threshold. This does not present a problem (when an exterior door opening is encountered) as the horizontal DPC’s terminate within the protective reveal wrap provided by the Type LTT.
The Type LTT by Cavity Trays of Yeovil promotes an easy route to compliance.
Upon completion and following installation of the frame and approach ramp/path, the Type LTT can be trimmed back on the outer face only so externally its presence is not visible.
