The traditional bay window is a good example of part of a building susceptible to lateral transference. As bay fascia/façade heights increase, so do the number of courses between the bay roof intersection level and the bay support lintel level. The greater the vertical distance between them, the greater the bay susceptibility to lateral transference because the exterior masonry skin on the outside of the bay runs uninterupted onto the support lintel spans the bay. Such construction permits a ‘sideways soak’. Severe storms can saturate masonry, and consequently wet rapidly soaks into the building and across the bay.

Horizontal transference between intersection level and lintel level can be prevented by building in a preformed DPC cavitray that vertically connects two levels within the same masonry skin without adversely interrupting bonding or coursing. Its presence arrests dampness before it can track inwardly.

Called a Bay Window Vertical Cavitray and manufactured by Cavity Trays of Yeovil, Type BWVC units are handed and available to suit brickwork and block work coursings. Units are introduced at each end of the lintel and provide a cleverly shaped permanent DPC connection upwardly to the lowest cavitray at roof intersection level. Wind-driven rain saturating masonry to the sides of the bay is thus prevented from continuing soaking inwardly where the exterior skin becomes an internal skin inside the bay.