Cavity trays and associated preformed units have become necessary in buildings to protect areas where the cavity tray is being 'bridged' by an opening such as doors/windows, or a protrusion such as a column or cladding support angles.

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Cavity trays and associates preformed units allow for water, which has made its way into the cavity either by wind driven rain or building settlement to be safely removed to the outside.

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The guidelines set in BS5628 pt3 (Materials and components design and workmanship) and BS8215 (Code of practice for installation of damp-proof courses) strongly recommend the use of cavity trays and associated preformed units. This recommendation is based on years of data showing the effect of water ingress on the fabric of the building and associated costs of remedial works.