Leadwork & Flashings Horsham

Correctly specified and installed lead flashing lasts 50 years or more — it’s one of the most durable materials on a roof when done properly. We use Code 5 lead as a minimum for flashings and valleys, hand-dressed to shape and treated with patination oil so it weathers evenly. What fails early is the wrong approach: under-spec lead, over-long pieces that split from thermal movement, or the mortar-and-mastic ‘flashing’ some firms use instead of proper lead, which cracks within a few winters. Done to standard, lead outlasts most other roof components. See Code 5 lead in our glossary.

Almost never. A leak at the chimney is usually the flashing — the lead that seals the junction between the stack and the roof — rather than the chimney itself, and renewing the flashing solves it without touching the masonry. Old mortar-based fillets crack and let water track behind them; proper stepped lead flashing with soakers, dressed into the brickwork, seals it permanently. Occasionally the stack also needs repointing while we’re there, but that’s a separate, minor job. Our chimney repairs page covers stack work if it’s needed alongside the flashing.

Sometimes — if a single section has lifted or a joint has opened but the lead is otherwise sound and correctly specified, a targeted repair is viable. But where the lead is under-spec, split from thermal movement, or was fitted as one over-long piece (a common cause of failure), replacement of that run in correctly-sized Code 5 lead is the lasting fix. We assess honestly: patching failing leadwork just brings you back to the same problem. Where it’s a mortar-and-mastic ‘repair’ someone did instead of proper lead, that always needs redoing properly.

A new lead flashing set around a chimney or abutment costs £400–£900 depending on the size of the stack and access; valley relining in lead runs £500–£1,200. A localised flashing repair is less. The cost reflects the lead itself (Code 5 is a substantial material), the hand-dressing skill involved, and scaffold or access. It’s more than a mastic smear, but it lasts 50 years rather than two or three, so it’s far better value over time. We itemise the leadwork clearly in the quote rather than bundling it into a vague figure.

Patination oil is a treatment applied to new lead immediately after installation, and yes — it matters, especially in exposed and coastal parts of West Sussex. New lead reacts with rainwater to form white carbonate staining that washes down and marks the masonry, tiles or render below. Patination oil prevents this initial reaction, letting the lead weather to its natural even grey without staining the surfaces beneath. It’s a standard part of a proper leadwork job — skipping it is a sign of a rushed installation, because the staining it prevents is unsightly and hard to remove afterwards.

We source Code 5 (and heavier where specified) lead from established roofing merchants, ensuring it meets BS EN 12588, the British and European standard for rolled lead sheet. What matters more than where it’s bought is that it’s the correct code (thickness) for the job — Code 5 minimum for valleys and flashings, heavier for larger or more exposed work — and that it’s installed to the Lead Sheet Association’s detailing guidance. Under-spec lead is a common corner-cut that fails early. We specify and install to standard, which is what makes leadwork last.

Signs a lead valley is failing include water staining on ceilings below the valley line, visible cracks or splits in the lead (often from thermal movement where over-long pieces were used), lead that’s become thin or brittle, and debris trapping water because the valley has distorted. Valleys backing onto trees — common near St Leonard’s Forest — fail sooner because trapped leaf litter holds water against the lead. If you can see the valley from a window or the ground and it looks cracked, rippled or patched, it’s worth a survey. Relining in correctly-sized Code 5 lead is the lasting fix.