Having lead flashings properly installed on your Cottenham property is the first step; knowing how to look after them is what keeps them watertight for the long term.
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Lead is the material of choice for sealing chimneys, dormers, parapet walls and flat roof abutments because it is malleable, long-lasting and does not corrode in the way ferrous metals do. A properly installed lead flashing, cut to the correct Code and fixed correctly, can outlast most other parts of a roof. The failures that do occur are nearly always traceable to a specific cause: the wrong Code of lead, mortar joints that have not been maintained, fixing methods that prevent thermal movement, or lengths of lead that are too long to expand and contract without splitting.
Understanding those causes means you know what to watch for and what simple maintenance will prevent the next problem.
Before looking at aftercare, it helps to know what a correctly installed flashing looks like. Step flashings on a chimney should be tucked into raked mortar joints on each course of brickwork, not just dressed over the surface of the brick. Each step should be a separate piece of lead, with the next piece lapping over it, so that thermal movement does not tear the metal. Soakers sit between the slates or tiles and are hidden from view - if they have been left out and the step flashing is doing their job as well, the junction will eventually fail.
A back gutter at the top of a chimney stack should be Code 5 or Code 6 lead on a wide stack, properly dressed into the mortar joint at the back. A flat roof upstand should be dressed up the wall face and turned into a mortar joint at a height that puts it above any standing water line. Lead that meets these standards needs very little intervention to keep performing.
A visual check once a year, and after any period of severe wind or frost, is enough for most properties. You do not need to get on the roof yourself - binoculars from the ground or from an upstairs window will show you most of what you need to see.
The mortar joints that hold step flashings in place deteriorate with frost and age. When the pointing fails, the lead can pull free from the brick at the top, and water runs straight in behind it. The lead itself may be in perfect condition - the fix is simply re-pointing the joint and re-dressing the lead back into place. This is a straightforward job for a roofer and, done promptly, it avoids a far more disruptive and expensive leak repair later.
The mortar used for re-pointing lead flashings should be a lime-based mix rather than a hard cement mix. Hard cement can crack more readily with thermal movement and can cause the brickwork to spall. If a contractor proposes using standard cement mortar, it is worth asking about a lime mix instead.
Blocked gutters are a cause of lead flashing problems that is often overlooked. When a gutter overflows against the base of a chimney or along a parapet wall, water sits against the lead and the mortar for extended periods. Even well-installed lead can eventually lose its pointing or allow water ingress at a lap if it is permanently saturated. Keeping gutters clear, particularly in autumn when leaves are falling, reduces the moisture load on every junction on the roof.
On flat roofs, making sure the surface drains freely and that debris does not build up against the upstand lead is worth doing every autumn. A pile of wet leaves sitting against a flat roof abutment for several months creates the conditions for mortar failure and eventual water ingress.
Mastic sealant, silicone and bitumen-based compounds are sometimes used to fill gaps at lead flashings. They are not an appropriate long-term fix. Sealant does not bond reliably to lead and cannot accommodate the thermal movement of the metal. It cracks and separates within a few years, often leaving a residue that makes proper repair harder when a roofer comes to re-dress or replace the lead. If you are tempted to apply sealant yourself to stop an active leak temporarily, be aware that this should be understood as a stopgap, not a solution.
Similarly, aerosol rubberised coatings or roof repair sprays are not suitable for lead work. They can trap moisture beneath them and make it harder to assess the condition of the lead underneath.
Some signs should prompt a call without delay rather than a wait-and-see approach.
Caught early, most of these are straightforward repairs. Left for a season or two, water tracking into the roof structure can cause timber decay, damp to internal plasterwork and damage to ceilings that costs far more to put right than the lead work itself.
The maintenance routine that keeps lead flashings performing comes down to a few simple habits: look at them once a year, keep the pointing in good order, keep gutters clear, and call a roofer when you see something that has changed. Lead that is inspected and maintained will outlast the rest of your roof covering by a considerable margin. Lead that is ignored until it leaks will fail earlier and cost more to put right.
If you had flashings installed some time ago and have never had them checked, having a roofer look at the pointing and the condition of the lead is a sensible step before a wet autumn arrives. A few minutes on a roof to re-dress a lifted flashing and re-point a joint can prevent a much larger job inside the house.
We carry out lead work installations, repairs and maintenance checks across Cottenham and the wider Cambridge area, including nearby places such as Histon, Waterbeach, Over and Cambridge itself. If you want a straightforward assessment of the condition of your lead flashings - on a chimney, dormer, flat roof or parapet - call us to arrange a roof survey. We will tell you what is sound, what needs attention and what you can do between visits to keep things in good order.
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Call any time. Calls are answered day and night and passed straight to our roofers.
