When building in natural stone, there are two popular methods of construction. The traditional method is to build against a backing skin of blockwork, behind which is the cavity and inner leaf. The result is an external leaf commonly around 250mm thick, as it really consists of two bonded materials. The alternative method that is rapidly gaining popularity is to dispense with the backing skin altogether, and instead build the external stone skin against a DPC barrier that separates outer and inner skins whilst maintaining a cavity gap with its moulded shape – the barrier being called Surecav.
In both instances, the resultant construction requires proportionally deeper protective DPC’s over openings and intersections, and Cavity Trays Ltd has now extended its range of products to address all such requirements.
The new house shown in the picture is built of Ham stone sourced from Somerset. The stone is coursed at 150mm. Where the gable abuts the end wall of the main house, preformed Muilticourse Cavitrays provide protection extending through the composite 250mm external skin and across and upwardly in the 75mm cavity. Each Multicourse tray is moulded with an inboard upstand that rises to link with the higher tray. The DPC arrangement formed follows above the roof pitch line and replicates the profile of a staircase – with connecting DPC treads and connecting DPC risers. The flashing is already bonded onto each tray and is shaped and angled for immediate dressing. The task of cutting and inserting separate flashings is eliminated.
Using preformed Cavitrays ensures the requirements of the Building Regulations are satisfied and dampness penetrating the exposed masonry above the abutting roof, is prevented from gravitating below the roofline.
Cavity Trays of Yeovil manufactures over 3,240 different tray permutations, for use in walls of all thicknesses, all coursing heights and all cavity widths. With the introduction of additional Multicourse and Multidepth Cavitrays this winter, the range has become even larger. The Yeovil-based Company is the only UK cavity tray manufacturer awarded European Technical Approval and every approved Cavitray is accompanied with a performance guarantee, valued by architects, users and customers of its products. The free take-off, scheduling and quotation service operated by Cavity Trays is available nationwide.
Property built with external Ham stone skin against a concrete backing block resulting in an overall skin thickness of 250mm followed by a 75mm cavity and a 100mm inner leaf. To comply with the building regulations the DPC Cavitray extends through the depth of the external skin and projects upwardly in the cavity.