If you have a leak tracing back to a chimney, skylight or roof valley in Diss, failing lead flashing is the most likely cause.
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Lead flashing is the strip of metal that seals the joint wherever your roof meets a vertical surface. Chimneys, dormer walls, skylights, abutments where a lean-to meets the main house - all of these rely on correctly fitted and maintained lead to stay watertight. When lead fails, water tracks under the tiles and into the roof structure before it ever shows on your ceiling. By the time you notice a stain, the timber and insulation beneath may already be wet.
Thetford Roofers carry out lead flashing installation and repair across Diss and the surrounding area. This page focuses on what to look for and why problems develop - because catching a lead failure early is almost always cheaper than repairing the damage it causes.
Lead problems rarely announce themselves dramatically. They tend to develop slowly, and the signs can be easy to mistake for something else. The following are the most reliable indicators that your lead work needs attention.
Any one of these is worth having looked at. Two or more together usually means the lead has reached the end of its serviceable life in that area.
Understanding why lead fails helps you judge whether a repair or a full replacement is the right call. There are several distinct causes, and they often overlap.
Lead expands and contracts with temperature. This is not a defect - it is physics. A well-fitted lead flashing uses stepped or soaker details and is dressed in sections with deliberate gaps to allow this movement. When lead is fitted in one continuous run that is too long, or is nailed through rather than clipped, the movement has nowhere to go. Over years, it works the lead loose or splits it at stress points. Splits that follow a straight line across a chimney apron flashing are almost always caused by restrained thermal movement.
A lot of lead failure we encounter is rooted in shortcuts taken at installation. Lead that is too thin for its position, mortar-bedded rather than clipped into a proper chase, or sealed with mastic rather than properly dressed - these all fail earlier than they should. Mastic fillets around skylights are a particularly common shortcut. They look tidy when new but typically last five to ten years before they crack and allow water in.
Lead is a long-lived material. Code 4 lead (the standard weight for most flashings) fitted correctly will typically last forty to sixty years. Code 3, which is lighter and sometimes used to save cost, has a shorter service life. Lead installed twenty or more years ago deserves a visual inspection even if you have not seen obvious signs of trouble. Fatigue cracks and lifted edges develop gradually and can be present for months before they cause a visible leak inside.
Moss and lichen hold moisture against lead surfaces. Over time this accelerates surface oxidation and, where roots get under the edge of a flashing, they can physically lift it. In valley positions especially, a build-up of debris behind a lead gutter or valley lining can cause standing water that wets the underlying timber even when the lead itself has no cracks.
Water trapped in a gap between lead and masonry can freeze in winter. Repeated freeze-thaw cycles widen the gap progressively. This is particularly relevant to chimney apron flashings where mortar pointing has already started to break down - once moisture gets behind the lead, frost accelerates the problem significantly.
A repair that simply applies new mastic over an existing flashing is unlikely to last. Proper lead work means removing the failed material, preparing the substrate, and fitting new lead correctly. At a chimney, this typically means:
At a skylight or rooflight, the approach depends on the frame type and the original installation. Sometimes the existing lead can be re-dressed if the material is still sound. More often, the lead needs replacing together with any self-adhesive underflashing tape that has failed beneath it.
Lead work pricing depends on access, the amount of lead needed and the condition of the surrounding masonry. As a general guide, a straightforward chimney re-flash on a standard semi-detached or detached property typically costs in the region of £300 to £600. More complex work - a large Victorian chimney stack with multiple flashings, a full valley reline, or work requiring scaffolding - will be higher. Valley lead lining typically runs from around £100 to £150 per linear metre for the lead and labour combined, though access and preparation can add to this. These are typical UK figures; get a specific price once the job has been properly looked at.
We carry out lead work in Diss and across the surrounding villages and towns. If you are within this area and have a lead flashing concern, call us to arrange a roof survey.
This is the question most homeowners ask. If the lead is structurally sound - not cracked through, not corroded to the point of thinning - and the failure is confined to the fixing or the pointing, a repair is often the right approach. If the lead itself is split, has been patched previously, or is the lightweight code 3 material that has been in place for twenty-plus years, replacement gives you better value over the next decade. A roofer who looks at the job properly should be able to give you a clear recommendation with a reason, not just push for the more expensive option.
If you have spotted any of the warning signs listed above, or if you simply have not had your flashings checked in a number of years, call Thetford Roofers to arrange a proper look. We will tell you what we find and what we recommend, without pressure.
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Call any time. Calls are answered day and night and passed straight to our roofers.
