The pitch of an abutting roof may be constant where it strikes a flat cavity wall, but if the wall is curved the actual angle of intersection changes throughout the slope. For a brief moment at the commencement of the slope the intersection may be horizontal, but as the wall turns the angle changes and those changes continue until the top of the roof slope.
Preformed curved Cavitrays by Cavity Trays of Yeovil are individually computer calculated to take into account the arc of the wall, the masonry coursing and the tray position up the slope. Each tray is numbered so the builder can literally lay by numbers – with assured interfacing and compatibility.
Cavitrays also take into account how the wall (and its flashings) will behave during storm conditions. A concave or convex wall accentuates the water-wash being blown across the curved surface. Provision must be made for weathering functionality into the direction of each flashing lap as well as with the direction of the lap.
The Cavitray lapping flashing arrangement provides a second layer of water arrestment and the flashing anchoring within a bosem jaw guards against capillary ingress.
The use of recessed pointing on any curved masonry is best avoided as it can act as a conduit along the wall surface. Flush pointing around flashings is favoured as it offers an uninterrupted consistent surface finish and promotes a solidity of masonry and tray bond. In terms of cost effectiveness, flush pointing also eliminates the need for further attention from the mason. Only the tray flashings require dressing later in the build programme.
Cavity Trays of Yeovil operates concept design and advisory services for which no charges are applied. The Company is the only cavity tray manufacturer awarded European Technical Approval.