What is a lead slate around a pipe?

A soil and vent pipe carries drainage gases up past the eaves, and where it pierces the roof there is a hole that must be sealed. On a slate or plain tile roof, the usual answer is a lead slate. It is a square or rectangular sheet of lead with a cone or boss formed in the middle, dressed up around the pipe. The flat part, called the apron, is slid under the course of slates above the pipe and laid over the courses below, the way a slate itself overlaps. Water reaching the pipe then runs onto the lead, round the collar and down the slope, never through the hole.

The top of the collar needs to grip the pipe, because a gap there lets rain run straight down inside. That is why the lead is dressed tight, and why the quality of the dressing matters more than the size of the sheet.

Lead is sold in numbered codes, which are simply thicknesses, so a bigger code means a thicker, weightier sheet. Leadworx names Code 4 as its general-purpose flashing choice, at 1.80 mm and 20.41 kg per m², and Code 3 as the lighter sheet used for soakers, at 1.32 mm. A pipe slate is a small piece that has to be bossed, meaning shaped with a mallet, into a collar, so a workable code that dresses without thinning is preferred. The quote names the code.

The same lead will outlast most other parts of the covering. MyJobQuote's 2026 guide says lead flashing can last over 80 years when correctly installed, and over 100 years for the higher codes. As ever, that is a typical figure that depends on workmanship, never a promise. If you want to compare the metals for flashings, our answer on copper or lead flashing sets them side by side.

Lead is soft and moves with the temperature, so the places where it has been bent hardest are where it tires first. On a pipe slate, the boss is the obvious one: hairline cracks form where the metal was stretched, and the collar can lift away from the pipe if the top edge was never tight. A slate nearby that has slipped can also expose the apron to the weather it was never meant to meet.

The signs inside the house are usually a brown ring on the ceiling around the pipe's line, or damp in the cupboard it runs through. Outside, look for a collar that stands proud of the pipe, a bright patch where the lead has been scratched, or a bead of mastic around the neck. That last one is often a sign someone has tried a quick fix, and our answer on whether sealant will fix a leaking lead joint explains why it does not usually last.

Because the apron slips under slates, a lead slate cannot be swapped without disturbing them. The slates around it are lifted, any that are cracked are set aside, the old lead is removed and a new one is dressed round the pipe, then the slates are put back. It is a small job done properly, rather than a patch done quickly. If the roof is tiled rather than slated, the principle is the same but the joints differ.

Because it is such a small item, the price is normally a line within a repair quote, not a job in its own right. For scale, MyJobQuote lists a chimney flashing patch at £150 to £250, which gives a sense of what small leadwork repairs cost nationally. The quote we write after the survey carries pictures taken on your own slope. A leaking pipe goes to the front of the list, and the priority on a first visit is keeping rain out. Once repaired, the work carries our 10-year workmanship guarantee in writing.

Not every pipe on every roof is dressed in lead. Some houses have a pre-formed collar in plastic or rubber, pushed over the pipe and tucked under the slates, and these are common on roofs re-covered at some point in the last few decades. They are quick to fit, but the seal at the neck can perish, and when it does the repair is a replacement of the whole collar.

Our habit on older slate roofs is to match what suits the roof. On a period house where the leadwork is otherwise lead, a lead slate keeps the detailing consistent and gives the repair a long life. On a newer roof with a pre-formed fitting, a like-for-like replacement may do. Either way the quote names which it is. Where a stack or vent pipe has been boxed in or moved during a conversion, we check the route inside as well, because a pipe that has been shifted can leave an old opening behind it.

People often confuse the two, since both are lead and both are hidden under slates. A soaker is a small rectangular piece, bent to an L shape, that is woven into the slate courses at an abutment against a wall or stack. A pipe slate is a single piece that surrounds a round pipe. The soakers belong to the wall junction, and our answer on what lead soakers are covers those.

The difference matters because a leak near a pipe may have nothing to do with the soakers, and a leak by a wall may not be the pipe. A survey taken both outside and in the loft tells us which, and we explain the cause in photographs. For the wider picture of leadwork across the roof, see lead roofing in Stroud.