Why does my lead-lined parapet gutter keep leaking?

On many older buildings the roof does not end at the eaves. A low wall, the parapet, rises above the edge of the slope, so rainwater cannot run off into an ordinary gutter. Instead a channel is built behind the parapet, lined with lead, to gather the water and carry it to an outlet at one end or in the middle. Where two roofs meet, for instance a pair of terraced houses sharing a ridge line, a similar channel sits in the valley between them and is called a box gutter.

Royston's table lists the heavier lead codes, Code 5 upwards, for parapet and box gutters, because the lining takes a lot of water and has to cope with movement. You find these gutters on Victorian terraces, chapels, shops with flats above and industrial buildings, and they are usually hidden from the street. Most people only learn one exists when a stain appears on an upstairs ceiling.

Because a parapet gutter is out of view, the evidence tends to arrive indoors. Look for brown rings spreading across an upper ceiling, damp that appears along the top of a wall after heavy rain, bubbling paint or wallpaper near the roof line, and a musty smell in a top-floor room. Damp that follows rainfall and dries off between showers points to the roof; damp that stays put may have another source.

In a loft or roof void, a torch may show dark, wet timber under the gutter, or daylight where the lining has lifted. Do not poke at damp plaster or climb up to look. A roofer reaches the gutter safely and photographs the lining, outlet and walls either side. The rest of our lead roofing pages describe the other places where lead lining protects a building.

Blocked outlets come first. Leaves, moss and debris build up, the water backs up, climbs past the lip of the lining and soaks into the wall or the roof structure. Next is the fall. A gutter laid with too shallow a gradient leaves puddles standing, and lead under constant water wears faster. Then there is movement. Lead lengthens in heat and pulls back in cold, so a long unbroken run with badly formed steps or laps tears where it is weakest.

The overflow matters too. A well-built parapet gutter has a way out for storm water if the outlet blocks, usually a weir or an overflow pipe through the parapet. If it was never fitted, or it has itself been blocked, an ordinary downpour can become a flood inside the building. Weathering of the parapet coping and its pointing adds a second route for water into the same area. Our old roof lead page covers how ageing sheet behaves.

Where the lining has plenty of life left and the trouble is a blocked outlet, a lifted edge or one crack, the repair is modest. The gutter is cleared, the damage is welded or patched, and the outlet is made free-flowing. Lead burning is the proper method for a crack, and a patch on its own is a weaker fix.

Where the lead is cracked in many places, thin from age or laid to poor falls, the gutter is relined. That means taking up the old lead, inspecting the boards and timbers beneath for rot, correcting the fall where possible, and laying new sheet in a suitable code with properly formed steps and drips. The outlet and overflow are renewed or cleaned at the same time. Relining is a bigger job, but a gutter that fails three times is dearer than one that is done once.

A self-adhesive tape or a coat of sealant over a split in a parapet gutter may stop a drip for a time. The trouble is that a gutter holds water for long spells, and any tape is under water and movement more than most of the roof. Our page on tape flashings against lead looks at where those products have a use.

When a gutter is pouring water into a building, we stop the damage spreading first, which can mean a temporary measure, and then set the lasting fix out in writing. Please do not climb to a parapet gutter to clear it yourself. The edge is exposed and the lining can be slippery. Our lead codes guide explains the sheet thicknesses a relined gutter might use.

Getting to a parapet gutter often means a scaffold or a tower, and sometimes access through a neighbouring roof. MyBuilder's scaffolding guide of August 2026 puts a typical two-storey house at around £850 to £1,200, and that figure shifts with the building. Lead costs are national typical figures; MyBuilder gives £150 to £200 or more per square metre for lead flat roofing. A gutter is a narrow strip, so the area is small, but the access can be the larger part of the price.

The survey photographs show the whole run: outlet, overflow, laps, steps and the wall either side. The written quote follows the visit, and the finished work is guaranteed for ten years in writing. Phone 01793 626096 or use WhatsApp.