Thetford Roofers carries out lead flashing installation and repair for homeowners in Brandon, tackling the failing seals around chimneys, valleys and skylights that cause most domestic roof leaks.
Lead flashing seals the joints where a roof surface meets a vertical element - a chimney stack, a parapet wall, a dormer, a skylight surround or the valley between two roof slopes. These junctions are the weakest points on any roof because two different materials are meeting, and both move slightly under temperature change at different rates. Lead handles that movement better than most materials, which is why it has been used on British roofs for centuries.
When lead is correctly installed, it can last 50 years or more before needing attention. When it fails, it tends to do so in ways that are predictable once you know what to look for. Understanding the warning signs - and what causes them - means you can act before a small flashing problem becomes a structural timber problem.
The main lead work elements on a typical house are:
Each of these is cut and formed on site from sheet lead. The thickness used - described as the lead code - matters. Code 3 is the lightest acceptable for most applications; code 4 or 5 is appropriate for wider flashings, back gutters and valley linings. Using the correct code is not pedantry: under-strength lead splits earlier and needs replacing sooner.
Most lead failures give you warning before water gets deep into the structure. These are the signs to look for, and what causes each one.
This is the most common presentation of a lead flashing failure. The patch typically appears or worsens after rain, often showing as a yellow-brown stain rather than obvious wet damage. It usually appears on the ceiling directly beside or on the chimney breast wall, but the water entry point may be higher up on the roof - water tracks along rafters before dripping down.
The cause is almost always a failure in the pointing that holds the top edge of the step flashing into the mortar chase in the brickwork. Frost is the primary driver: hairline cracks in the mortar let in water, which freezes, expands, and opens the crack further. After several winters, the pointing drops out and the flashing lifts away from the wall at the top edge. Rain then runs directly behind it.
You can sometimes see this from the ground or from an upstairs window. A section of flashing that sits lower than it should, or that has a visible gap at the top where it meets the brickwork, has likely worked loose from the chase. This happens when mortar pointing fails and the lead is no longer held at the top. It can also happen when the lead was not properly wedged and pointed in the original installation.
A slipped flashing is not necessarily a full replacement job. If the lead itself is in good condition - no splits, no cracks, adequate thickness - it can sometimes be re-dressed back into position, the chase re-cut and re-pointed, and the job is done. The roofer needs to assess the lead condition before committing to repair versus replacement.
Lead develops fine cracks over time through a process called fatigue cracking, caused by repeated thermal cycling. The lead expands in summer heat and contracts in winter cold, year after year. Flashings that were installed without adequate expansion joints - typically a 150mm overlap between adjacent pieces at intervals - crack earlier because the thermal movement has nowhere to go. Narrow flashings and those in exposed positions tend to show this first.
Splits that run across the width of a flashing are a sign the lead has reached the end of its serviceable life and needs replacing. A repair patch over a split will flex differently and is unlikely to hold long-term.
A degree of surface rippling is normal in aged lead - it is a soft material and moves with the building. But pronounced buckling, where the lead no longer sits flat against the roof surface, can indicate that the lead is lifting at the edges, or that there is a build-up of debris underneath it. Once the seal is broken at the edges, water can track under the lead rather than being directed off it.
Buckling at the base of a chimney back gutter is a common place for this to occur, particularly where autumn leaf fall packs against the stack year after year. Debris against lead accelerates oxidation and can physically push the edge of the flashing away from the wall over time.
White efflorescence - a powdery white deposit on brick or mortar - is salt being drawn to the surface by moisture. If it appears on brickwork near a flashing, it is a sign that water has been getting into the wall at that point. The flashing may be the entry point, or the brickwork itself may be porous. Either way, it is worth having the flashing and the pointing checked.
Moss establishes itself where debris and moisture collect. If it is growing at the edge of a valley lining or at the base of a chimney flashing, it is holding moisture against the lead continuously. Over time, moss roots work under flashing edges and lift them. Clearing moss from these areas before it reaches that stage is straightforward maintenance; clearing it after it has lifted a flashing edge is part of a repair job.
Beyond normal wear and frost damage, there are several specific causes of early lead failure worth knowing about:
Chimney flashing repairs run from around £150 to £400 for a single side. A full re-flash of a chimney stack - step flashing, soakers, back gutter and front apron - typically costs £400 to £900 depending on the size of the stack and access. Valley relining generally runs from £300 to £700 for a standard domestic valley. These are realistic working ranges; the specific price depends on what the inspection reveals about the condition of the existing lead, mortar and surrounding tiles.
From our base in Thetford we cover Brandon and the surrounding area, including Mundford, Mildenhall, Methwold, Feltwell, Watton, Croxton, Barnham, Elveden, Kilverstone, East Wretham and Brettenham. If you are in a village nearby and unsure whether we cover your location, call us.
If you have spotted any of the warning signs above - damp near a chimney, visible gaps in flashing, moss at valley edges - call Thetford Roofers to arrange a roof survey. We will inspect the lead work, explain what we find and give you a price before anything is touched.
No obligation · We usually respond within 2 hours
Storm damage, active leak, damaged ridge - we aim to be on-site within 24 hours.
