Chapter 1: Why is our shallow slate roof on a Yateley Green house letting water in?
What we find
A shallow-pitched slate roof relies on overlap. Each slate covers the joint between the two below it, and the head lap, the distance one course reaches down over the next-but-one, is what stops water running back up the slope in a gale. On a low pitch that lap needs to be generous. If the slates have slipped even a little, the overlap shrinks and wind-driven rain finds its way through.
Nineteenth-century roofs of this type are also due a close look at the details. Lead valleys between two slopes can split along the folds, and the nails in the slates rust. In the loft, look for stained rafters beside the valley or a damp patch near the eaves. Outside, slipped slates make a ragged line, and broken ones leave bare timber showing.
What we fix
We start in the loft, tracing the leak back to its source with photographs, then check how far the slates have slipped and whether the battens are still sound. Most of the time the right repair is to refix the sound slates with new copper or stainless nails, replace the cracked ones with matching stock and renew a failed lead valley, without touching the rest of the roof.
If the battens have rotted across the slope, or the slates are flaking in layers, a re-slate is the honest answer. Typical UK ranges for natural slate re-roofing sit between £120 and £180 a square metre, with man-made slate at £90 to £130; your fixed quote follows the survey. Inside the conservation area we keep to slate and check consent. See our slate roofing page for the options.