Church in St Helier, Jersey Channel Islands

Type of works: supply and installation of cavity trays.

The church in St Helier was approximately ten years old, with brick cavity walls and stone mullion style features. There was severe damp penetration around two side-by-side gothic arches and also around a circular window positioned just above and partially between both arches.

Rainwater penetrating the masonry above, in and around the circular window was being channelled around the perimeter of the circular window. The penetrating water was then discharging at the bottom of the circle (approximately six o’clock) into a small area between the two arches. Thus dampness was manifesting at the bottom of the circular window, and around the tops and sides of the arches.

All three openings were of mullion style stonework. Solid mullions are prone to transmit dampness through their solid composition and the concentration of water in the immediate vicinity was overwhelming the ability of the mullions to prevent or minimise ingress. Thus the mullions were acting as a bridge from exterior to interior.

It was necessary to introduce an effective new DPC arrangement to protect the circular window plus the gothic arches, and at the same time direct rainwater away from these features.

A modified circular Type K cavitray was proposed incorporating side projecting horizontal arresting barriers at three o’clock and six o’clock. Each arresting barrier would promote penetrating water to be discharged at the far ends of each barrier, well away from the arches and mullion features. Type W caviweeps/cavivents to provide an evacuation path.

Type BA curved cavitrays were proposed to protect the gothic arches. Extended sides act in the same way as the higher arresting barriers. Type Ws provide an evacuation path.

The extent of penetrating water running around the circular window was quite severe, and the proximity of the gothic arches and their shape meant the water was originally accumulating in the worst possible area. Cavity Trays' two-fold solution relocated concentrations of water and cavitrays protected the three openings. The dampness problem was eliminated following installation of thecompany's recommended products.