Lead Flashing Repair: Why Your Roof Leaks Around the Chimney
If you've noticed a damp patch on the ceiling near your chimney, there's a good chance the lead flashing has failed. Flashing is the weatherproof seal between your roof covering and the chimney stack, and when it fails, water gets in. It's one of the most common roofing repairs across {location} and the whole of the UK.
What Is Lead Flashing?
Lead flashing is sheets of lead fitted where the roof tiles meet the chimney brickwork. There are several pieces involved:
- Step flashing — stepped pieces running up the side of the chimney, overlapping each tile course
- Back gutter — a lead-lined channel behind the chimney where water flows down to the tiles below
- Front apron — a single sheet across the front of the chimney base
- Cover flashing — lead pieces chased into the mortar joints of the chimney to overlap the step flashing
Each piece relies on the others. If one fails, water finds a path in.
Why Does Lead Flashing Fail?
Lead is extremely durable — properly installed, it can last 50 to 100 years. But several things cause premature failure:
- Thermal movement — lead expands and contracts significantly with temperature changes, and if the sheets are too large they can crack or fatigue
- Mortar deterioration — the mortar holding the lead into the chimney joints crumbles over time, allowing the lead to pull free
- Poor original installation — lead that wasn't fitted to the Lead Sheet Association standards may have been cut too thin, lapped incorrectly, or fixed with silicone instead of proper mortar pointing
- Storm damage — high winds can lift unsecured edges
Signs Your Flashing Needs Repair
From inside the property, the classic sign is a damp stain on the ceiling or wall near the chimney, particularly after rainfall or driving wind. From outside, you might see:
- Lead lifting away from the brickwork
- Gaps between the lead and the mortar joints
- Cracked or split lead sheets
- Old repairs using silicone sealant (a temporary bodge that always fails eventually)
The Repair Process
A competent roofer will assess whether the flashing can be re-dressed and re-pointed or whether it needs full replacement. The typical process for replacement involves:
- Carefully removing the old lead and cleaning out the mortar joints
- Cutting new lead to the correct code (thickness) — Code 4 for step flashings, Code 5 for back gutters
- Chasing the new lead into the brickwork joints and pointing with a proper lead sealant or lime mortar
- Ensuring all overlaps and drip edges are correct to prevent wind-driven rain ingress
Cost of Lead Flashing Repair in {location}
A straightforward re-point and re-dress of existing lead typically costs £150 to £350. Full replacement of chimney flashings ranges from £400 to £900 depending on chimney size, roof access and whether scaffolding is required. Always get a written quote from an NFRC-registered roofer.
Don't Accept Quick Fixes
Be cautious of anyone who suggests coating the flashing with sealant or bitumen paint. These are temporary measures that mask the problem and make proper repairs harder later. Lead is the proven material for flashing — it's been used on British roofs for centuries because nothing else matches its combination of flexibility, durability and weather resistance.
If you suspect your chimney flashing is failing, get it inspected before the next heavy rain. A small repair now prevents serious water damage to your {location} property later.