Yeovil-based Cavity Trays has developed a ready-to-use solution to eliminate a recurring construction problem when building on contaminated land. Originally conceived for Radon gas situations, it is called the Type PAT – Protective Adjustable Threshold.
Where gas barriers are present within the external cavity walls of a building and the door openings interrupt the arrangement, maintaining gas-tight integrity and damp-proofing measures is always difficult. Commonly door openings are at a different level (access requirements) and interrupt the protective arrangement against rising gas.
Using a flexible DPC requires support from higher courses and creates a cumbersome arrangement in which achieving a gas and water-tight arrangement that links with threshold and closers is difficult.
The Type PAT eliminates this problem by providing both gas and water protection under and to the sides of every opening, and does so in a way that eliminates discontinuity and provides adjustable connection with adjacent barriers.
The three-dimensional DPC unit is bedded within the external wall opening, with integration between wall barriers and the Type PAT achieved using the adjustable side connectors that attach and then slide up and down to the requisite level. The cavity face of each connector has a projecting connection profiled to match that of the external wall DPC/barrier profile. Once in position, all lapping sections are lap-sealed and gas-tape bonded. The footprint membrane is integrated in the usual way to maintain gas-resistant integrity.
The DPC threshold unit is usually supplied in three sections consisting of two corners and an infilling channel base length. These three components overlap so always accommodate the as-built structural opening width. Wider openings of any dimension can be formed by introducing additional lapping channel base lengths across the opening and sealing using gas-grade bonding strip.
The reveal closers (compatible caviclosers available) descend into the cavity-projecting sides of the Type PAT, terminating within its channel base in which are located flexible drainage conduits. (This channel base can additionally accommodate an optional insulating strip if thermal enhancement is sought under the sill).
The fins on the closers provide capillary breaks in the reveal closing arrangement, and allow water to gravitate between fins for discharge at the closer base. The flexible conduit provides the water escape route, without compromising Type PAT continuous gas protection across the base of the opening.
