Newmarket Roofers carries out lead flashing repairs and replacements for homeowners in Fordham, and we know that a good job means the maintenance afterwards matters just as much as the installation.
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Lead flashing seals the junctions where your roof meets vertical surfaces - chimney stacks, dormer walls, bay window roofs, parapet walls, and flat roof abutments. It is shaped and dressed by hand to fit the specific profile of each junction, then turned into mortar joints above and lapped over tiles or slates below. Done correctly, it creates a watertight detail that is far more durable than any sealant-based alternative.
Lead work should be hand-dressed on site to BS EN 12588 standard. This covers the alloy composition and the code (thickness) of the lead, which must be matched to the area being covered. Using the correct code is not optional - lead that is too thin will crack through thermal movement in a matter of years.
Cracked lead, lifting flashings and dropped pointing are the most common causes of roof leaks around chimneys, dormers and bay windows. A single crack or gap in flashing is enough to let water in during sustained rain, and because the water often tracks along a rafter before appearing inside, the damp patch is rarely directly below the source.
A common problem is lead that was installed without proper expansion joints - long continuous runs that eventually crack under repeated thermal movement. Another is step flashing that was bedded on top of masonry rather than turned into the mortar joints, which means it lifts away from the wall as the mortar beneath it degrades.
For a chimney, a full re-flash includes a back-gutter at the high side of the stack, stepped flashings on both sides following each tile or slate course, and an apron flashing across the front. Each section is dressed individually and overlaps the section below it. The top of each piece is turned into a raked mortar joint and pointed to keep water out. For valley work, the lead is laid in overlapping sections to the correct fall and width for the roof pitch.
Once the lead is in place, it should sit tight against every surface it covers. There should be no gaps, no sealant used to cover poorly fitted sections, and no lead that is simply nailed flat rather than dressed into the profile of the junction. Good lead work looks neat and purposeful.
This is something homeowners rarely think about until a problem reappears - but simple, regular checks can prevent the next call-out. Lead work does not need specialist maintenance, but it does benefit from attention. Here is what to look for and what to do.
Once a year - ideally in autumn before the wetter months - it is worth looking at each area of lead work from the ground, using binoculars if needed. You are looking for:
None of these checks require getting on the roof. If you see anything that concerns you, have it looked at by a roofer before the next heavy rainfall rather than waiting until water appears inside.
The mortar joint above a lead flashing is what holds it against the wall and prevents water from getting behind it. Pointing deteriorates over time, particularly on older properties where lime mortar is used. A failed joint above the flashing is one of the most common causes of a leak in an otherwise sound piece of lead work.
Repointing a flashing joint is a relatively minor piece of work if caught early. Left for several years, water that has been getting behind the flashing may have caused more significant damage to the masonry or the timber beneath it, making the eventual repair more involved.
Lead valleys carry a significant volume of water off the roof. If leaves and debris build up in the valley, they hold moisture against the lead and can also cause water to back up behind the flashing at the low end of the valley. Clearing gutters and valleys at least once a year - more often if there are trees nearby - reduces the load on the lead and helps it last longer.
Debris also accumulates at the base of chimney stacks, in the internal angle between the stack and the slope. This area is often where the back-gutter sits, and a build-up of wet leaves there will accelerate any deterioration in the lead beneath them.
Bitumen sealant and similar products are sometimes used to patch a visible crack in lead flashing. This can be an acceptable short-term measure in some circumstances, but it is not a permanent repair and it should not become a habit. Sealant shrinks and cracks over time, it can obscure underlying problems, and it makes proper lead work harder to carry out later because the area needs cleaning back first. If a crack reappears after sealant has been applied, the lead itself needs assessing.
Heavy moss growth on tiles adjacent to lead work contributes to debris build-up at flashings and valleys. It also retains moisture, which is not ideal for any of the materials nearby. If moss is significant, having it treated and cleared is worthwhile - not primarily for the lead, but for the overall health of the roof covering. Avoid high-pressure washing directly at or near lead flashings, as this can force water behind them and may dislodge pointing.
Strong wind can dislodge individual sections of flashing, particularly where fixings have already begun to loosen over time. After a period of severe weather, a visual check of any lead-work areas is sensible. A section that has partially lifted can often be re-fixed straightforwardly; the same section left for a full winter can allow enough water in to cause a much larger problem internally.
Correctly specified and installed lead sheet typically lasts several decades. The precise figure depends on the code used, the quality of the original installation, and how well the surrounding details - pointing, tiles, gutters - are maintained. Lead that was installed using an insufficient code, or without proper expansion joints, will fail much sooner regardless of how well the rest of the roof is maintained.
Chimney flashing repairs typically cost between £200 and £500. A full chimney re-flash with back-gutter, step flashings and apron generally ranges from £600 to £1,200 depending on the size of the stack and access requirements. Valley replacements are priced by the linear metre. These are typical UK ranges - the actual figure will depend on the specific condition and configuration of your roof.
Proactive maintenance - keeping pointing in good order and dealing with small issues before they develop - reliably reduces the total cost of keeping lead work serviceable over the life of the roof.
If you have spotted something on your annual check, or if it has been some years since the lead work on your property was looked at, call us to arrange a proper survey. We will give you a clear picture of what is in good order and what needs attention.
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Call any time. Calls are answered day and night and passed straight to our roofers.
