Chapter 1: Why does our Victorian villa in Haslemere leak at the valley where two roof slopes meet?
What we find
A valley is the trough where two roof slopes meet at an internal angle, and it carries the run-off of both slopes. On a villa with several gables and bays, the valleys take a lot of water. Many Victorian valleys were lined with lead laid in long sheets, and lead can crack where it has expanded and contracted for a century or more. In other valleys the tiles were cut tightly to a mortar bed, and that bed has since cracked and washed out.
Leaks at a valley show up in an odd place. Water runs down the trough, finds a split and drops onto the timbers below, then travels along a rafter before it reaches a ceiling. So a damp patch in a bedroom may be a metre or more from the real fault. In the garden, look for a dark streak along the valley, moss in the trough or tiles that have shifted on either side.
What we fix
We start from the roof and the loft together, tracing the stain back along the timbers to the point of entry. Where the lead is sound but has lifted at the edges, it can be dressed back and the tile cuts tidied. Where the sheet has split along a fold or the underlay beneath it has perished, the honest repair is to lift the tiles either side and re-line the valley with new lead, with fresh underlay under it. Our guide to the lead valley explains how the sheet is laid and why the width matters.
Some owners ask about swapping lead for glass-reinforced plastic, and we compare both in lead valleys against GRP valleys. Either way, the photographs we take show you the damaged section, and the fixed quote follows once we have surveyed it.