Ely Roofers carries out lead flashing installation and repair for homeowners in March - and if you are dealing with an active leak right now, this page explains what to do while you wait and what to leave well alone.
Lead flashing is the weatherproofing detail at every junction where a roof surface meets a vertical element - a chimney stack, a dormer wall, a parapet, or the valley line between two roof slopes. When it is correctly fitted using code 4 or code 5 lead sheet dressed to British Standard, it is one of the most durable details on any roof. When it fails - through age, poor original installation, or physical damage - it becomes one of the most reliable ways for water to get into a building.
Lead flashing should be carried out by experienced tradespeople using the correct code of lead for the application and fixed to British Standard, not laid in mastic and left.
The most common point of failure is the mortar pointing that holds the top edge of the flashing into the masonry joint. This weathers out over years, the lead lifts slightly, and wind drives rain in behind it. Step flashings on chimney stacks - the individual pieces that interleave with tile or slate courses up each side of the stack - are particularly prone to this because there are many separate pieces, each with its own pointing joint.
Valley lead can split along the centre line after years of thermal movement, especially if the original installation used undersized lead or bays that were too long. Lead on flat roof upstands can pull away from the wall if it was not fixed with clips and relied entirely on mortar to hold it. In all these cases, the failure point is usually hidden from view and water travels some distance before appearing inside the building.
If water is coming in during rain and you are waiting for a roofer to attend, there are sensible steps that limit damage without making the underlying problem worse.
Place a container under any active drip and use old towels around it to stop water spreading across the floor. If the ceiling is bulging with trapped water, the water has pooled above a membrane or layer of paint. A small, deliberate hole made at the lowest point of the bulge - with a screwdriver, centrally in the bulge - allows the water to drain in a controlled way rather than the ceiling coming down across a wider area. This sounds counterintuitive but it reduces structural damage to the ceiling and the water below.
Move anything valuable away from below the leak. Note precisely where the drip or damp appears relative to the room - which side of the chimney breast, how far from the wall, whether it is at the ceiling or tracking down a wall. That information helps a roofer work out where on the roof they need to look. With lead work, the point where water appears inside is rarely directly below the entry point.
A look in the loft during rain, or immediately after, can locate where water is entering the roof structure before it finds its way to the ceiling. A torch held at an angle across rafters and purlins will show wet patches or staining. If you can identify which rafter or area is wet, that is useful information for the roofer. Do not attempt to go further than the loft - do not go onto the roof slope itself.
This section matters. Well-meaning attempts to fix lead work problems without the right skills and materials can make the eventual repair more expensive and more difficult.
Roofing sealant applied to a lifted or cracked flashing appears to stop the leak in the short term. The problem is that lead continues to move with temperature changes - expanding in warmth and contracting in cold. That movement breaks the sealant bond within months. Worse, the sealant traps moisture against the lead surface and accelerates corrosion beneath it. What would have been a straightforward repair becomes a more involved job because the lead underneath has deteriorated. A roofer who arrives to find sealant has been applied has to remove it before they can properly assess the condition of the lead beneath.
Lead is soft and looks easy to work, but dressing it correctly around corners and into masonry joints without cracking it takes practice. Forcing lead that has lifted back into place without the right tools usually cracks or stretches it, and a cracked flashing lets in more water than a lifted one. Raking out masonry joints for re-pointing also needs to be done correctly - too deep and you undermine the brickwork; too shallow and the mortar will not key properly.
Pitched roofs are dangerous to walk on without the correct equipment and experience. The risk of a fall is serious. A wet roof is more dangerous still. Roofers use proper access equipment for a reason - there is no safe way for a homeowner to inspect or work on a pitched roof without it. Leave the roof itself to the contractor.
If a previous repair attempt has left a layer of flash band (self-adhesive bitumen tape), sealant or other temporary fix, do not add another layer on top. Stacking temporary fixes makes the eventual permanent repair harder and does not stop the underlying problem. Call a roofer instead.
A proper lead work inspection involves getting on the roof and examining the flashing detail at close range. For a chimney stack, that means checking the step flashings up both sides, the cover flashing across the front face, the back gutter behind the stack, and the apron at the base. For a valley, it means lifting any tiles that are covering the lead edge to see the full width and condition of the valley lining. A visual inspection from ground level or from a bedroom window is not sufficient to diagnose a lead work failure - the roofer needs to be at the detail itself.
Once the problem is identified, you should be told clearly what has failed, why, and what the options are. For isolated failures on otherwise sound lead, a repair is often the right call. For lead that has reached the end of its life or was poorly fitted originally, replacement gives a better long-term result.
Repair work on chimney step flashings - re-dressing and re-pointing without replacing the lead - typically falls in the range of £150-£400 for a standard domestic chimney, depending on how many sections need attention. Full lead replacement on a chimney stack (step flashings, cover, back gutter and apron) using code 4 or 5 lead is more commonly in the range of £500-£900. Valley lead replacement varies with length but rarely comes in below £400 even on a short run. These are UK-wide typical ranges - the actual figure for your roof depends on what is found on inspection.
If you have an active leak or you can see lead flashing that has lifted or cracked, call Ely Roofers to arrange a proper roof survey. We cover March and the surrounding area from our base in Ely. The sooner a lead work failure is properly assessed and repaired, the less damage it does to the structure beneath.
No obligation · We usually respond within 2 hours
Storm damage, active leak, damaged ridge - we aim to be on-site within 24 hours.
