Why valleys need lead lining
A valley collects and channels water from two roof planes at once, making it one of the highest-flow points on the whole roof — a material that can handle that volume reliably is essential.
Open vs closed valleys
Lead-lined open valleys, where the lead is visible between the tiles or slates, tend to perform more reliably long-term than closed valleys where tiles overlap and hide the junction.
Installation on Bristol's older roofs
Fitting a new lead valley on an older roof means matching the existing tile or slate coursing carefully so the finished valley sheds water cleanly rather than creating new pinch points.