Dry Valley

• Working Procedure
• Construction Sequence
• Components
• Documents

1. Dry Valley Troughs are designed to fit directly onto either 6mm continuous ply boards laid continuously over the rafters or 12mm ply or 19mm softwood set between the rafters and supported on timber noggings. Minimum total width of the boards is 360mm.

2. The valley boards should be lined with a 1m wide strip of underlay lapped into the gutter.

3. Starting from the foot of the valley, notch the fascia and shape the bottom of the valley to allow the valley to discharge into the gutter. Lay a length of valley trough on the valley boards and both firmly press down to support its base and press together to minimise the gap in the central upstand section. Nail the sides to the valley boards at a maximum 500mm centres. Lay subsequent valley trough lengths up the roof allowing a minimum overlap of 150mm when measured vertically. Where valleys intersect, a code 4 lead saddle should be used.

4. Lay the underlay and battens in the normal manner, ensuring that the underlay is lapped over the outer water bar of the valley trough. The battens are cut so that they locate onto the flat fixing edges of the valley trough and are nailed through into the supporting valley boards.

5. Install the slates/tiles in the appropriate manner cutting as normal into the valley abutting the raised central upstand. Where appropriate, use bonded double tiles or tile and a half to avoid small unsupported tile cuts.