Poorly fitted or failed lead flashing is a common cause of roof leaks in homes, and getting it right first time saves a great deal of money and disruption.
Lead is the traditional material used wherever two roof surfaces meet, wherever a roof meets a wall, and wherever a chimney or skylight breaks through the roof surface. When it is correctly fitted, it lasts for decades without attention. When it fails - through poor installation, movement, or simply old age - water finds its way in almost immediately.
The main types of lead work on a typical house are flashings (the horizontal strips that seal the join between a roof slope and a vertical surface), soakers (small interlocking pieces that sit beneath slates or tiles at a hip or verge), valleys (the channel that runs down where two roof slopes meet), and flat roof coverings laid entirely in lead sheet. Each requires a different approach and a different code of lead sheet.
Lead sheet is sold in codes that refer to its thickness. Code 3 and Code 4 are used for soakers and lighter flashings. Code 4 and Code 5 are standard for step and cover flashings on chimneys and dormers. Code 6 is used for valleys and flat roof areas. Using the wrong code - something that happens more often than it should - means the lead will fatigue and crack far sooner than it ought to.
The most common cause of lead failure is not old age but thermal movement. Lead expands and contracts with temperature changes, and if a piece is dressed over too long a length without a proper drip or lap, it will split or pull away from the mortar. A single flashing run should not exceed 1.5 metres without an appropriate lap to allow for movement.
Mortar tucked into the back of a flashing is another weak point. Many older properties have flashings that were pointed in with ordinary sand and cement, which bonds poorly to lead and cracks away over time. The correct method is to fix the flashing into a raked mortar joint using lead wedges, then point over with a flexible sealant or a lead mastic. Ordinary mortar will always fail eventually.
Common signs that lead work needs attention include:
Oxide staining is not itself a sign of failure - lead naturally oxidises and the run-off can mark the tiles below - but it does show you exactly where your lead is and whether it has moved from its original position.
Lead work pricing varies according to the type of job, the access required and how much material is needed. Re-flashing a chimney stack will vary in cost depending on its size and the number of sides that need flashing. A lead valley replacement depends on the size of the roof and the access required. Flat roof areas covered in lead sheet cost more per square metre than felt or EPDM rubber, though lead flat roofs are less common on modern properties.
Scaffold or tower access adds to the cost, but is sometimes unavoidable for safety and for doing the job properly. A roofer working off a ladder cannot dress lead accurately or apply the correct fixing method, so quotes that avoid scaffold on a high or steep roof should be questioned.
If you have spotted a leak or noticed signs of failed lead work, you may have a few days before a roofer can get to you. What you do - and what you avoid doing - in that time matters. A small amount of sensible action now can prevent water damage from spreading inside the property while the roof is still awaiting repair.
Move any furniture, rugs or belongings out from beneath the damp area. Water can travel a surprising distance between the point it enters the roof and the point where it shows on a ceiling, so check a wider area than just the visible stain. Place a waterproof sheet or tarpaulin beneath the affected ceiling section and use a bucket or container to catch any drips.
If a ceiling is bulging, this means water has pooled above the plasterboard. A ceiling in this condition can come down suddenly and without warning, taking the plaster with it. Carefully pierce the lowest point of the bulge with a thin screwdriver or skewer to let the water drain in a controlled way into a bucket. This is not a pleasant job but it is far better than a sudden ceiling collapse.
Photograph the leak from inside and, if you can do so safely from ground level or a window, from outside too. Note when it started, whether it worsens during rain and whether it seems to correspond with a specific area of the roof. This information is genuinely useful to a roofer before they go up and helps them target the right part of the roof straightaway. A damp patch on a ceiling does not always sit directly below the fault.
If the water has reached ceiling insulation or loft boards, increase ventilation in the loft space if you can do so safely by opening any existing vents. Wet insulation loses its thermal properties and can harbour mould if it stays damp for too long. If you can access the loft, placing a fan at the hatch can help move air through.
Most buildings insurance policies cover sudden and unexpected water ingress, but many exclude gradual deterioration. If the lead failure appears to have happened suddenly, notify your insurer and document everything with photographs and dates. If an insurer is involved, do not authorise permanent repair work until the claim has been noted, though temporary protection is usually acceptable.
Lead work is a skilled trade. The materials, the fixing method and the sequence in which sections are installed all affect whether the finished job will remain weathertight for years or fail within months. There are things a homeowner can reasonably do in an emergency, but there is a clear line between sensible protection and making a problem worse.
This sounds obvious, but homeowners do attempt it. A roof surface is not designed to be walked on by an untrained person without the right equipment and knowledge of where to place their weight. Tiles and slates crack under point loading in the wrong place. Lead sheet is particularly vulnerable - a misplaced foot can crack or permanently distort it. Falls from roofs cause serious injuries every year. Unless you are a trained roofer with appropriate equipment, stay off the roof entirely.
Silicone is often reached for as an emergency fix for a leaking flashing. The problem is that silicone does not bond reliably to lead, lifts within a few freeze-thaw cycles, and leaves a residue that makes a proper repair harder to carry out cleanly. If a roofer finds silicone over a lead joint, they have to remove it before they can assess and fix the underlying problem. It adds time and cost to the job.
Butyl or flashing tape is sometimes used as an emergency temporary fix in the trade, but it is not a substitute for proper lead work. It lifts, it traps moisture beneath it, and it can mask the extent of the problem. If you apply tape to buy a few days before a roofer arrives, make sure you tell the roofer what you have done so they can remove it before carrying out a proper inspection.
A failed mortar joint behind a flashing looks like a straightforward pointing job, but it is not. To re-fix a flashing properly, the old lead has to come out, the joint has to be raked back, the lead reflashed into position with correct wedging, and then pointed. Simply packing new mortar over old, cracked pointing will not hold. Water will find the gaps within a single winter.
A dry stain does not mean the problem has gone away. Lead failures and cracked flashings often only leak during driving rain or when wind pushes water in a particular direction. Between those conditions the ceiling dries out and the stain fades. Waiting until a dry stain reappears as an active drip usually means the water has been entering and exiting the roof structure repeatedly, which increases the risk of rot in timbers and of the leak eventually reaching through to the plasterwork below.
Before any lead work is carried out, you should have a clear idea of what is being done and why. A roofer who cannot explain the fault in plain terms should prompt caution. Reasonable questions to ask include:
Correctly installed lead flashing in a sheltered position, using the appropriate code, can last 60 years or more. In a more exposed position or on a chimney that runs hot and cold regularly, 40 to 50 years is a realistic expectation. These are material lifespans based on industry data - not a promise from any individual contractor.
Lead valleys are found on older properties where two roof pitches meet. A valley collects rainwater from two slopes and channels it to a gutter, so any failure in the valley lead allows water directly into the roof structure. Valleys are prone to cracking at the centre where water runs fastest, and to lifting at the edges where they tuck beneath the tiles or slates.
Replacing a lead valley involves stripping back the tiles or slates on both sides, removing the old lead, checking the timber valley board beneath for rot, and installing new lead in correctly lapped sections. The tiles or slates are then relaid. It is a more involved job than re-flashing a chimney and typically takes a day or more depending on the roof size.
Flat roof areas in lead sheet are less common than felt or EPDM rubber systems on modern properties, but older homes sometimes have lead-covered flat roofs over bay windows, extensions or porches. These are dressed in carefully overlapping sections with drips formed at each step to prevent capillary action. When properly installed, a lead flat roof needs very little maintenance.
All lead work is exposed to wind and rain over time, and older houses with original chimney stacks and tiled valleys are particularly worth checking if lead work has not been attended to in many years.
If you are in Spixworth or a neighbouring village and you are concerned about a leak or have spotted signs of failed lead work, call us for a roof survey. A good roofer should explain exactly what is wrong, what is needed to fix it, and what it will cost before any work starts.
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