Most roof leaks don't start in the middle of a slope of tiles. They tend to start at the joints: where the roof meets a chimney, a wall, a dormer or another roof slope. On many homes, those joints are protected by lead.
Because leadwork sits in places that are hard to see from the ground, problems can go unnoticed until water shows up inside. This guide explains what roof leadwork does, where it is found, the signs it may need attention and why a quick fix isn't always the right one.
What does leadwork do on a roof?
Lead is used to weatherproof the junctions and changes of direction on a roof. It can be shaped by hand to follow brickwork, tiles and slates, which makes it well suited to awkward details where a tile or slate alone can't keep water out.
Its job is to direct rainwater away from the joint and back onto the roof covering or into the gutter. When it is fitted, fixed and lapped correctly, it can last for many years. When it is damaged, poorly fixed or has moved, water can find its way behind it.
Where is lead commonly found on a roof?
Depending on the property, you may find lead in some or all of these places:
- Chimney flashings, including the front apron, side soakers or steps and the back gutter
- Abutment flashings, where a roof meets a wall
- Valleys, where two roof slopes meet
- Around dormer windows and their cheeks
- Around rooflights and some roof windows
- Bay window roofs and small canopies
- Ridges, hips and some flat roof areas on older properties
Cracked, split, lifted or slipped lead
Lead expands and contracts with changes in temperature. Over time, and particularly where pieces were fitted too long or fixed too tightly, that movement can cause it to crack or split. Even a small split can let water track underneath.
Lead can also lift at the edges, often after high winds, or slip down a roof where its fixings have failed. Flashings that are tucked into brickwork are normally held in a mortar joint. If that mortar has crumbled away, the top edge of the flashing can pull out of the wall, leaving a gap.
From the ground, signs to look for include lead that looks raised, bent or out of line, gaps between the lead and the wall, and pieces that appear to be missing or loose.
Problems around chimney flashing
Chimneys are one of the most common sources of leadwork problems. A chimney has several separate pieces of lead working together, and a fault in any one of them can let water in.
Typical issues include flashings that have come away from the brickwork, mortar joints that need repointing, a blocked or damaged back gutter behind the stack, and earlier repairs made with sealant or mortar fillets that have since cracked.
Because the chimney itself can also let in water through porous brickwork or damaged flaunching, a leak near a chimney isn't always caused by the lead. That is why an inspection of the whole stack is useful before deciding on a repair. Our chimney repairs page explains more about the stack itself.
Lead valleys and water ingress
A valley carries a large amount of water off two roof slopes, so it works harder than most parts of a roof. Lead valleys can wear thin, split, or become blocked with moss, leaves and debris, which makes water back up and spill over the edges of the lead.
On some older roofs, valley lead was laid in long single lengths. These can be more prone to splitting because the lead has less room to move. Where the timbers beneath the valley have softened, the lead may also sag and hold water.
Signs of a valley problem can include damp patches on a ceiling below the valley, water staining on timbers in the loft, and tiles or slates along the valley edge that have slipped or become loose.
Signs you may notice inside the property
Leadwork problems are often first noticed from inside. Signs that may point to a fault at a roof junction include:
- Damp patches or brown staining on ceilings, particularly near a chimney breast or below a valley
- Damp on the chimney breast in an upstairs room or loft
- Wet or stained timbers in the loft near a chimney, dormer or valley
- Peeling paint or blown plaster where an internal wall meets the roof
- A leak that only appears in heavy or wind-driven rain
What these signs don't tell you on their own
Water can travel some distance along timbers or membranes before it shows, so a damp patch doesn't always sit directly below the fault. Condensation and other building issues can also cause staining. Our guide to finding where a roof leak is coming from goes into this in more detail.
Why older leadwork can fail
Well-fitted lead can have a long working life, but it isn't permanent. Common reasons older leadwork fails include:
- Thermal movement over many years, leading to splits and cracks
- Pieces fitted longer than they should be, with too little room to move
- Mortar pointing that has broken down and released the top of a flashing
- Lead that is too thin for the job it is doing
- Previous repairs using sealant, tape or mortar that have since failed
- Debris and moss holding water against the lead
- Theft or deliberate damage in some cases
Older properties
Older properties often have original or long-standing leadwork, together with chimneys, bay roofs and dormers that rely on it. In towns with a lot of period housing, such as Leamington Spa, it is common to find lead that has been patched several times over the years rather than renewed.
Can leadwork be repaired, or does it need replacing?
It depends on the condition of the lead and the cause of the problem. Some faults can be dealt with as a repair, for example re-fixing and repointing a flashing that has come out of a mortar joint, or replacing a single damaged section.
Where the lead is split in several places, worn thin, poorly detailed or too long to move properly, renewing that section is often the more reliable option. In a valley, for example, the lead may need to be lifted and replaced along with any damaged supporting boards.
The right answer depends on what is found once the area is properly inspected. The leadwork page explains the work we carry out on flashings, valleys and other roof details.
Why sealing over damaged lead isn't always a long-term repair
Applying sealant, mastic or a repair tape over a split can stop water for a while, and it may be a sensible temporary measure while a permanent repair is arranged. It doesn't normally deal with the reason the lead failed.
If the lead split because it can't expand and contract properly, it will keep moving after it has been sealed. Sealants can also harden and crack with sunlight and weather, and they can trap water behind the lead rather than shedding it. A layer of sealant can also make the underlying problem harder to see on a later inspection.
A longer-lasting repair usually involves correcting the detail itself: the size and fixing of the lead, the laps, the pointing and any damaged material beneath it.
When is a professional inspection sensible?
It is worth arranging an inspection if you can see damaged or displaced lead from the ground, if damp appears near a chimney, dormer or valley, after high winds, or if a leak keeps coming back after an earlier repair.
Please don't climb onto the roof to check yourself. Leadwork sits at height and often in awkward places, and it should be inspected with safe access. Photographs taken from the ground or from a window can be a helpful starting point when you get in touch.
If you've noticed signs of a leak but aren't sure where it is coming from, our roof repairs service covers finding and fixing the cause, whether that turns out to be the lead or another part of the roof.
Concerned about the leadwork on your roof?
If you're in Coventry, Leamington Spa or the surrounding areas and think your leadwork may need attention, get in touch and tell us what you've noticed. Photographs and details of when any leak appears help us decide on the right next step.
Think your leadwork needs repairing?
Tell The Roofing Lads where you've noticed the problem and send photographs where available, and we can discuss the next step for inspecting and repairing it.