Which lead code is used for chimney flashing?

Lead for roofing is graded by code, a number from 3 to 8, and the code is a class of thickness and weight. A bigger number means thicker, heavier sheet. Each code carries a colour mark so it can be told apart on site: code 3 is green, 4 blue, 5 red, 6 black, 7 white and 8 orange.

Weight is the plain way to see the difference. Royston Lead's brochure gives code 4 at 20.41 kg per square metre, code 5 at 25.40 and code 6 at 30.05. That extra weight is extra metal on the roof, which helps where the sheet is dressed over angles and exposed to movement. It also costs more. So the code printed on a quote is worth reading, and worth asking about if it is missing, because it tells you what is actually going onto your stack, and it is a fair question to ask any roofer.

For flashings, the strips sealing the junction between stack and roof, Royston Lead lists codes 4, 5 and 6. Code 3 is described as recommended for lead soakers only, the small folded pieces slipped under each tile or slate at the edge of the stack. The table sets out the thicknesses and the uses Royston gives.

A stack uses lead in several places: an apron, stepped pieces up the sides, a back gutter behind and the soakers. Our page on stepped flashing shows the stepped pieces, and the lead is chosen for each part separately.

Nothing says every piece of lead on a house must share a code. The back gutter behind a wide stack carries more water than a narrow side strip, so it can justify heavier sheet than the soakers beside it. A stack on an exposed gable takes more weather than one tucked between two pitches. A flashing that has to be bent round awkward angles may suit a different code from a plain straight run.

We decide that at the survey, standing at the stack, and tell you which code we recommend and why. You do not need to know metals to follow the answer, since it is the same plain explanation we give about the repair itself. You receive a single total in writing, so if you are weighing up several quotes, ask each roofer which code they will use for the flashings and which for the soakers. A quote that is silent on it deserves a question.

Lead is among the longest-lived roofing metals, which is why it has been dressed round chimneys for so long. MyJobQuote's lead guide, last updated on 22 September 2026, reckons lead flashing can serve for more than 80 years. Read that as a typical lifespan, not a guarantee, since it assumes the lead has been fitted well. What usually cuts the life of a chimney flashing short is rarely the metal. It is the way the metal is held in.

The edges are lodged in the mortar joints of the stack, and once that mortar crumbles, the lead loosens and lifts. Sealant smeared across a gap, thin sheet stretched over a sharp angle, and bends worked too many times all shorten the life of the sheet. Dressing lead into raked-out joints and pointing it properly is what holds a repair together. Our pages on chimney flashing and lead flashing cost cover both.

Begin with which code goes where. Ask whether the soakers are lead or something else, and whether the back gutter is the same code as the aprons. Ask how the lead will be secured into the brickwork, and whether the old joints will be raked out and repointed. Ask what is happening to the flaunching and the pointing around the flashing, since new lead set in old, crumbling mortar will not stay put.

MyJobQuote gives typical UK prices of £150 to £250 for a patch of lead, and £350 to £460 to renew all the flashings round a stack with no scaffold, climbing to £700 to £920 where scaffold is needed. These are national guide prices, and ours is set after the survey. Because access can double the figure, see scaffolding for chimney repairs, and the chimney repairs hub for the full list of work.