Valley replacement

A valley is the internal angle where two roof slopes meet, and it carries all the rainwater from both of them down to the gutter. On older Irish roofs it is usually lined with lead, sometimes with mortar and tiles laid into it. Over time the lead splits along its length because it was laid in pieces too long to expand and contract freely, or it corrodes, or the mortar along its edges falls out and water runs in under the slates. Leaks from valleys tend to show inside as a stain in the corner of an upstairs room, or along a line in the attic. Replacing a valley means stripping the slates or tiles back on each side, taking out the old lining, checking and repairing the boards and timbers beneath, which have often rotted after years of slow leaks, and fitting a new lining. Lead is laid in lengths short enough to move, with proper laps. A GRP valley gives a seamless, long lasting channel. A preformed dry valley is quick and suits many tiled roofs. The slates or tiles are then cut and relaid along each side with the right gap to the centre, so leaves and moss can wash through instead of damming the channel.

Keeping it clear

A valley that fills with moss and leaves overflows sideways under the slates. Once it is new, keep it clear. We check and clear valleys as part of a yearly roof check, which costs far less than another replacement.