Question answered
Lead parapet gutters: repairs
The short answer
A parapet gutter leaks when its lead lining splits, its outlet blocks, or its falls are too shallow and water ponds against a seam. The repair follows the cause: clearing the outlet or patching one split is often enough, while a lining that is cracked throughout, or was laid without proper falls, usually needs relaying.
A lead parapet gutter sits behind a wall, out of sight, so its faults show first as a ceiling stain or a damp patch on an inner wall. The causes are few, and each can be traced.
Why water gets through a gutter built to hold it
A parapet gutter is a shallow lead-lined channel between the foot of a roof slope and a low wall, with an outlet at one end or in the middle. It is meant to carry water away, but it is also the one place on the roof where water stands for a while, and that makes every weakness in it count.
The usual causes are a split in the lead, a seam that has opened, a blocked outlet that lets the water rise above the lining, and a wall-side upstand that has pulled away from the brickwork. Water that rises past the edge of the lead runs into the wall or under the first tiles and shows up a long way from the fault.
Because the channel is hidden behind the parapet, owners rarely see it until it fails. A look from a ladder soon after rain, with the ponding still visible, tells us more than the stain does. You get photographs of your own gutter, so the fault is not left to guesswork.
Drips and falls: how the lead is shaped to drain
Lead is laid in lengths, and each length steps down to the next. That step is called a drip, and it lets the gutter fall towards its outlet while keeping the joints above the water line. Where a gutter is long, there are several drips, each tall enough to stop water creeping back up.
The fall counts for as much as the lead. Flat-roof guidance from IKO, citing the 2018 edition of BS 6229 (since revised), recommends a finished fall of at least 1:80, with 1:40 as the design figure so tolerances and deflection are absorbed. A gutter bed is a narrow flat roof, so that is the margin we look for. Where the timber deck has sagged, water sits in the hollow and works at the lead until it tires.
Lining is usually code 5 or code 6 lead, the grades Leadworx lists for general and large roof work. Thinner sheet is easier to lay but has less in reserve when it moves with the weather.
Outlets, overflows and ponding
Outlets block with moss, leaves, bird nests and bits of broken tile. When that happens in a storm, the gutter fills and the water looks for the lowest edge, which is often the wall side. An overflow pipe through the parapet gives it somewhere harmless to go, and a gutter without one relies entirely on the outlet staying clear.
Ponding is a different fault. A puddle that stays after the rain has stopped means the falls are wrong, the deck has dipped, or a drip is too low. Standing water speeds up the cracking of old lead and leaves a white crust on the surface that is easy to mistake for dirt.
Clearing an outlet costs little and belongs in any yearly look at the roof. If the gutter ponds even when it is clean, the outlet is not the problem, and the repair has to go deeper than a clear-out.
Patch, bossing or relay
A single split in a long lining may take a lead patch, or a new piece welded in, provided the surrounding lead is sound. A seam that has opened can often be reworked without lifting the whole gutter. Those are the smaller jobs, and they hold while the lead around them has life left.
When cracks appear in several places, or run along the length of a sheet, patching only moves the problem on. Relaying means stripping back to the deck, correcting the falls with new tapered timbers, fitting fresh underlay and laying new lead with the right drips and upstands. It costs more than a repair, and it is the sounder answer once the gutter has failed generally.
A bead of sealant over a split is only a stop-gap; does lead flashing sealant work explains why. The upstand against the wall is held with wedges, covered on lead flashing wedges.
What we check before quoting
We start inside, tracing tide marks and wet timber up to the gutter, then go outside to match them. The questions are simple: where is the lead split, does water pond, is the outlet clear, and is the deck sound underneath. Photographs of your own gutter are included with the quote, which is a written total for the job. We also note the state of the parapet coping and the downpipe, because they feed the same channel.
Work at height over a pavement may need a scaffold licence from the highway authority, which the scaffold firm arranges. If you hold two quotes against each other, ask each roofer whether it covers scaffolding and VAT, since those can move the total a long way.
If water is coming in, we make it safe first and discuss the permanent repair afterwards. For typical UK ranges see lead roofing cost, and for everything else we do with the metal visit our lead roofing page.
Parapet gutter queries
Can a parapet gutter be fixed from the roof without scaffolding?
Sometimes. A clear-out, a small patch or a seam reworked at roof level can be done from the roof or a roof ladder if the access is safe. Anything that needs the lining lifted, a new deck or a new outlet usually needs proper access, and the survey tells us which applies.
Is a damp patch on the inner wall always the gutter?
No. Damp on an inner wall can come from the gutter, a failed upstand, a cracked parapet coping or a leaking downpipe. Following the marks from the inside, then checking outdoors, shows where the water actually enters before any repair is priced.
Tell us about your roof
Describe what is happening and we will call you back to arrange a visit.
- Photographs of what we find
- A written quote with one total price
- Or call 01903 299063
10-year workmanship guarantee, in writing.