Getting the lead work right on your Sawston property is only half the story; knowing how to look after it afterwards is what stops you calling a roofer again in five years.
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Lead flashings seal the junctions between your roof and any vertical surface it meets: the four sides of a chimney stack, the cheeks and head of a dormer, the edge of a flat roof where it abuts a house wall, and the line where a lean-to or outbuilding roof meets the main structure. These are the points on any roof most exposed to wind-driven rain, and they are the points that most often let water in when the seal breaks down.
A properly installed lead flashing, cut and dressed to the correct Code specification, is one of the most durable materials in roofing. Code 4 lead on a standard chimney flashing should last many decades. Code 5 on an exposed flat roof upstand is similarly long-lived. The problems arise not from lead wearing out under normal conditions, but from poor installation, inadequate fixings, or maintenance being left too long.
Before we get to aftercare, it helps to understand what a correctly finished lead work job should look like, because that's the baseline you're maintaining. On a chimney, the lead covers the front apron (below the lower edge of the stack), the two sets of stepped flashings running up each side, and the back gutter behind the stack at the highest point. All four elements are needed; a chimney with three sound flashings and a failed back gutter will still let water in.
The lead is fixed with lead clips or tacks at the correct intervals, pressed into the mortar joint or brick chase at the top, and then repointed with mortar to hold it in place. The pointing is as important as the lead: if the mortar is too hard, it doesn't flex with the lead's movement and cracks open. If it's too soft, it erodes and the flashing gradually drops away from the wall.
Typical lead work costs on a standard chimney in Cambridgeshire run from around £300 to £700. A full re-lead of a larger or more complex stack will be at the upper end or beyond. Individual repairs to a single section are often in the £150 to £300 range. These figures assume the correct Code lead, proper fixings and a finished mortar chase.
Lead flashings do not need intensive maintenance, but a visual check once a year saves a great deal of trouble. Autumn, before the worst of the wet weather sets in, is a practical time to do this. You do not need to go onto the roof; a good pair of binoculars from ground level will show you what you need to see.
Here is what to look for:
You can extend the life of lead flashings without going anywhere near them. The single most useful thing a homeowner can do is keep gutters clear. Blocked gutters cause water to back up and overflow, and that overflow often ends up running down a chimney stack or dormer cheek, straight behind the flashing. Gutter clearance once a year, or twice if there are overhanging trees, removes a significant source of water ingress.
On properties with a chimney, check that the chimney pot and cowl are intact. A cracked pot lets water straight down the flue, and the water often finds its way out through the base of the stack, which appears to confirm a flashing problem when the actual cause is the pot. A roofer who doesn't look at the pot when investigating a chimney leak is missing a step.
If a chimney is no longer in use, having it capped professionally is good practice. An open flue draws rain straight down, and the damp rising from below can deteriorate the lead and mortar work at the base of the stack from the inside.
The temptation to apply a sealant or roofing mastic to a lifting or cracked flashing is understandable, but it causes more problems than it solves. Sealant over a lifted lead flashing doesn't address the underlying movement; it just traps moisture behind the flashing, which accelerates corrosion of any metal fixings and often makes the subsequent repair harder and more expensive. A roofer then has to strip the sealant before the proper repair can begin.
Similarly, pushing a lifted flashing back by hand and leaving it is not a repair. Without re-fixing the clip and re-pointing the chase, it will lift again at the next frost or windy spell.
If a visual check from ground level shows any of the following, arrange a proper roof inspection rather than leaving it until spring:
A leaking flashing left over a winter will cause damage to timber roof structure, ceiling plaster, and insulation that costs significantly more to fix than the flashing itself would have.
Lead flashings don't exist in isolation. On a slate or tile roof, the condition of the surrounding slates or tiles matters too. A cracked slate directly above a chimney step flashing will direct water into exactly the joint the flashing is meant to protect. Any flashing inspection should include a look at the tiles or slates immediately surrounding the flashed junction.
On flat roof sections, the lead upstand and the flat roof membrane need to work together. A sound lead upstand on a failing felt or EPDM membrane will still let water in. These two elements should be assessed at the same time.
We carry out lead work on chimneys, dormers, flat roof abutments and parapets for homeowners in Sawston and nearby. If your last flashing job didn't hold, or you want to get ahead of a problem before it becomes a leak, call us to arrange a roof survey.
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Call any time. Calls are answered day and night and passed straight to our roofers.
