When lead flashing fails on a Stalham roof, the damage that follows is nearly always avoidable - here is what good lead work involves, and how to keep it sound for years after the job is done.
Lead is the most reliable weatherproofing material available for the junctions on a pitched or flat roof. Flashings seal the join between a roof slope and a chimney stack, parapet wall or dormer. Valleys channel rainwater from two meeting slopes down to the gutters. Soakers sit under each course of slate or tile beside a chimney or abutment, doing invisible but essential work every time it rains. When any of these fail, water finds a way through.
Poorly fitted lead is one of the most common causes of roof leaks. The problem is rarely the lead itself - it is either lead that was cut too short, fixed incorrectly, or fitted without the right code weight for the application. A flashing that looks fine from the ground can be lifting at the edges, cracking at bends, or simply not lapped far enough to keep wind-driven rain out.
Good lead work means cutting and dressing lead sheet on site, forming correct drips and laps, and fixing with the right clips and fixings rather than relying on sealant to paper over poor workmanship. Sealant has a place as a secondary measure, but it should never be the primary reason a flashing stays watertight.
Each job uses code-appropriate lead sheet. The code number refers to the thickness: Code 3 is used for soakers, Code 4 and 5 for most flashings, and Code 5 or 6 for valleys and flat areas where the sheet carries more water and foot traffic. Using the wrong code is a false economy - thinner lead splits sooner and heavier lead is wasted cost.
You do not need to get on the roof to spot early warning signs. Look from an upstairs window or from the garden with a pair of binoculars. Common problems include:
A water stain on a ceiling does not always appear directly below the leak point. Water can travel along a rafter or batten for some distance before dripping, so the visible damage inside is often offset from the actual entry point outside. This is why a proper inspection checks the lead work on the roof rather than just looking at the stain from below.
Good lead work starts with preparation. That means clearing the area, checking the underlying timbers and felt for any rot or damage caused by the previous leak, and making sure the surface the lead will sit on is sound. There is no point fitting new lead over a rotten roof batten.
The lead is then cut to size and dressed by hand. Step flashings are formed so each piece overlaps the one below by at least 65mm, and the upstand into the wall chase is deep enough - typically 25mm minimum - to stay locked in even when the mortar is repointed. Valley lead is formed with a code-5 or code-6 sheet, with a central water channel wide enough to prevent debris blocking the flow.
Fixings matter. Lead clips or tacks hold flashings at intervals without restricting the natural thermal movement of the sheet. Lead expands and contracts with temperature changes. If a flashing is fixed rigidly over too large an area, or if the bends are too sharp, it will crack. Traditional lead work accounts for this by forming bays of the right length and leaving the correct clearance at joints.
The mortar chase is repointed after the lead is positioned - not before. The lead is tucked into the chase, the joint is raked out and repointed with a lime or proprietary mortar suited to the masonry. Pointing over the top of old lead that has already pulled away from the chase is a temporary fix at best.
Lead work costs vary depending on the type of job and the amount of lead required. As a general guide, replacing step and cover flashings to a chimney on a standard semi-detached house typically costs in the region of £300 to £600, depending on the number of faces and the access needed. Valley lead replacement on a single valley can run from £400 to £800 or more. Flat roof lead coverings on a small bay window roof are often in the £500 to £1,200 range depending on the area covered and the code of lead used.
These are typical UK figures and will vary with the specific details of your roof. The best way to get an accurate figure is to have the job looked at properly before any work starts, so you know exactly what needs doing and why.
This is the section most roofers skip, and it is the one that will save you money. Good lead work, properly fitted, should perform well for decades without attention. But there are straightforward things you can do - or ask a roofer to check - that prevent a small issue becoming a roof leak, and prevent a roof leak becoming a ceiling replacement.
Once a year - autumn is a good time, before the wet season - look at the lead work on your roof from a safe vantage point. You are looking for any visible gaps, lifted edges, or mortar that has dropped out of the joint above a flashing. Binoculars make this practical without getting on a ladder. If anything looks different from last year, get it checked.
After any significant storm, it is worth a quick look too. Lead work that was already marginal can be shifted by wind pressure under a lifted edge. Catching it then rather than waiting for the next heavy rain saves the repair bill plus the cost of any internal water damage.
Blocked gutters cause water to back up. When water backs up behind a gutter, it can get under the bottom course of tiles and behind the apron flashing at the eaves. This is not strictly a lead failure, but it produces the same result - water in the roof structure. Clearing gutters at least once a year, and after heavy leaf fall, is simple maintenance that protects the work.
Lead valleys need to be kept clear of debris too. A valley clogged with leaves and silt forces water to spill sideways under the tile edges. The lead itself may be perfectly sound, but a blocked valley will produce a leak just as surely as a failed one. This can usually be cleared from a ladder rather than needing a roofer, but be careful not to damage the lead surface or the tile edges when doing so.
The mortar that holds a flashing into its chase, and the pointing in the brickwork above it, are exposed to the same freeze-thaw cycles as the rest of the chimney or wall. Mortar is not permanent. On a chimney that is regularly inspected, the pointing above a flashing typically needs refreshing every ten to fifteen years, sometimes longer, depending on the mortar mix used and the exposure of the chimney.
If the pointing cracks or drops out, water gets into the chase from above and can track behind the flashing even if the lead itself is sound. Repointing the chase is a straightforward job and far cheaper than replacing the flashing prematurely because the mortar failure was missed. Ask your roofer to look at the pointing above every flashing when they carry out any roof work.
This is one of the most common DIY mistakes. Sealant applied over a lifted or cracked flashing will slow the leak for a season or two, but it also locks in moisture, prevents you from seeing what is happening underneath, and can make a proper repair significantly harder and more expensive when someone eventually needs to do the job properly. If a flashing is lifting or leaking, the right answer is to refix or replace it, not to seal over the problem.
There is a specific case where sealant is used by a qualified roofer: as a secondary bead on certain pipe collars and penetrations where the lead is formed around an irregular surface. This is different from slapping a bead of mastic over a step flashing that has pulled away from the wall.
If a builder or chimney specialist works on your chimney stack - repointing, replacing pots, fitting a liner or cap - the lead work around the base of the stack should be checked and reset if necessary. Vibration from drilling, or movement of the stack during work, can disturb flashings that were previously well bedded. This is easy to overlook and easy to check. It is worth specifying it when you book any chimney work.
Lead flashings fitted correctly with the appropriate code sheet are expected to last 50 to 100 years in normal conditions. Valley lead and flat roof lead coverings, where thermal movement is greater and foot traffic more likely, have a shorter typical lifespan - generally 40 to 60 years for well-fitted work. These are material performance figures, not guarantees on any particular job.
The limiting factor is usually not the lead itself but the mortar, the underlying timbers, or maintenance that was never done. A flashing that pulls away from a chase because the mortar was never repointed, or a valley that splits because a roofer walked across it without protection, has failed early for reasons that proper care would have prevented.
We cover Stalham and the surrounding area, including North Walsham, Aylsham and villages nearby. If your property is in this part of Norfolk and you have a lead work job that needs a proper look, call us to arrange a roof survey.
Whether you are getting quotes from us or from another roofer, these are the right questions to ask:
A roofer who can give clear, specific answers to these questions is one who knows the work. Vague answers about "doing a good job" or "sorting it out" are not reassuring when you are talking about work that should last decades.
If you can see lead that is lifting, cracked or pulling away from a wall, or if you have a leak you suspect is coming from a flashing or valley, call us to arrange a proper roof survey. We will inspect the lead work, explain exactly what has failed and why, and give you a straight answer on what needs doing before any work starts.
No obligation · We usually respond within 2 hours
Storm damage, active leak, damaged ridge - we aim to be on-site within 24 hours.
