A traditional stone-built farmhouse on the outskirts of Coniston had been suffering from persistent leaks where two roof slopes met at a deep valley. Our valley repair specialists removed the corroded lead lining, replaced deteriorated timber boarding, and installed new Code 5 lead valley with properly formed welted joints — permanently solving a problem that had plagued the property for years.
This 200-year-old Lakeland farmhouse sits at the base of the Old Man of Coniston, where two substantial roof wings create a deep valley channel approximately 5 metres long. The original lead valley lining had been in place for over 80 years and had finally failed — heavy corrosion had eaten through the lead at the base of the valley where standing water collected, and the overlap joints between lead sheets had separated due to decades of thermal cycling. Every period of sustained rain brought water into the bedroom below, causing extensive damage to the lath-and-plaster ceiling and the oak floor joists beneath. A previous attempt to repair the valley using bituminous sealant had temporarily slowed the leak but trapped moisture against the timber boarding underneath, accelerating rot in the valley boards themselves. The homeowner had been managing the leak with buckets for two winters before calling our valley repair team.
We stripped the valley completely back to the rafters, removing all old lead, corroded fixings, and the rotted timber boarding. Inspection revealed that two of the valley rafter timbers also had surface rot where water had been pooling, so we treated these with a specialist timber hardener and reinforced each one with a bolted sister rafter in pressure-treated C24 timber. New 25mm marine-grade plywood boarding was installed across the full valley length, providing a smooth, stable substrate for the new lead. We then lined the valley with Code 5 milled lead sheet, laid in three bays with properly formed welted drip joints between each bay to accommodate thermal expansion. The lead was dressed 150mm up under the Westmorland slate courses on both sides and secured with copper clips rather than nails to allow thermal movement. A lead splash lap was formed at the base where the valley discharges into the gutter, preventing water from overshooting in heavy downpours.
The new Code 5 lead valley is rated for a minimum 100-year service life when properly maintained. The welted drip joints eliminate the expansion cracking that destroyed the original continuous sheet, and the increased fall achieved by re-boarding ensures water flows freely without pooling. The homeowner's leak problem was immediately and permanently solved — no water has entered since completion despite significant rainfall. The ceiling below was subsequently replastered, and there has been zero recurrence of damp. We issued a 25-year guarantee on all valley repair work and lead installation.
Code 5 lead (weighing 25kg per square metre) was specified for this valley repair because it provides the optimum balance of durability and workability for valley applications. Milled lead is produced by rolling rather than casting, giving it a consistent thickness and smooth surface that works beautifully into complex valley details. At this thickness, Code 5 lead has a life expectancy exceeding 100 years in normal conditions. The lead was supplied by an LSA-certified manufacturer and carries full traceability documentation, confirming it meets BS EN 12588 standards for roofing lead.
The valley boards were replaced with 25mm WBP (Weather and Boil Proof) marine-grade plywood, which uses phenolic resin adhesive between its layers to resist delamination even when exposed to persistent moisture. This is critical in a valley application where any boarding failure beneath the lead could create local dips that hold standing water. The plywood was pre-treated with a preservative coating on both faces before installation.
The two sister rafters were specified in C24 strength-graded softwood with Tanalith E pressure treatment, providing resistance to fungal decay and insect attack for the life of the building. C24 grade provides the structural capacity needed for a heavily loaded valley position where snow and rainwater concentrate from both roof slopes above.
Rather than nailing the lead directly to the substrate — which would restrict thermal movement and eventually cause fatigue cracking — we secured the lead using copper clips at 450mm centres along both edges. Copper is galvanically compatible with lead, preventing corrosion at the fixing points that would occur with steel or aluminium alternatives.
If your roof valley is leaking, showing corrosion, or has separated joints, contact our experienced valley repair team for a free inspection. We serve Coniston and all surrounding Lake District villages with expert lead valley replacement and repair. Don't let a leaking valley cause costly structural damage — call us today for a no-obligation quotation.
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