In short
If the damp is on the ceiling beside the chimney breast and worst after rain, it is the flashing. If it is on the chimney breast itself, high up and on the weather side, it is the pointing. Often it is both, because the flashing is let into the mortar joints, so when we scaffold a stack for one we check the other.
This is a job for our Leadwork service.
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Two jobs, one scaffold
Repointing and leadwork are separate trades on a big site, but on a house chimney in west Norfolk they are the same visit. The lead is wedged into a chase cut in a mortar joint. If the joints are gone, the lead has nothing to hold it. If the lead is gone, water runs behind the joints. Doing one without checking the other is how a stack gets scaffolded twice.
Signs it is the flashing
- Damp on the ceiling either side of the breast, or in the loft on the rafters next to the stack.
- You can see the lead has lifted, curled, or been sealed with mastic by somebody before you.
- The back gutter behind the stack, on the uphill side, holds leaves and water.
- The lead is thin and creased. Older stacks often have code 3 lead where the job wants code 4 or 5.
Signs it is the pointing
- Damp on the chimney breast in a bedroom, worst on the side the weather comes from.
- Joints recessed deeper than a finger, sand washing out of them, or bricks that have spalled.
- Cracked flaunching around the pots.
Which lead we use
Lead sheet is graded by code, which is its thickness. Leadworx's guide lists code 4 at 1.80mm and code 5 at 2.24mm, and both they and the Lead Lads' guide describe code 4 as the general choice for step flashings and cover flashings, with code 5 for back gutters and the wider, more exposed pieces where extra stiffness pays. That is how we form a stack: code 4 for the steps and apron, code 5 for the back gutter and the tray, all to BS EN 12588 sheet. Code 3 is for soakers, and where we find it used as a flashing on a coastal stack at Hunstanton it is normally the reason for the call.
| Detail | Code we use | Why |
|---|---|---|
| Soakers under the tiles | 3 | Thin, hidden, must bend under a tile |
| Step flashing and front apron | 4 | Standard exposed flashing |
| Back gutter and chimney tray | 5 | Water concentrates there, needs stiffness |
What we recommend
If the scaffold is going up for either job, price the other while it is there. MyJobQuote's 2026 chimney guide lists scaffolding at £300 to £600 on its own, which is often more than the difference between doing one job and doing both. We will photograph the stack from the scaffold and tell you which of the two it actually needs; sometimes the lead is fine and it is only the top three courses that want doing.
