When Should Chimney Leadwork Be Renewed?

There Are Four Pieces, Not One

Before the decision makes sense, the components: a chimney passing through a pitched roof has a front apron below it, stepped side flashings with soakers underneath them down each side, and a back gutter above it.

They are separate pieces of lead doing separate jobs, and they fail at different rates. Aprons split from thermal movement. Side flashings pull out of their chases. Back gutters silt up and corrode from standing water and debris. Soakers slip or were never there.

So "the leadwork has failed" is rarely accurate. Usually one of the four has, and the question is what to do about the other three.

When Patching Is the Right Answer

When the failure has a specific, local cause and the rest is genuinely in good order. A back gutter that has silted and corroded on a stack whose side flashings and apron are sound is a back gutter job.

When the lead is a different age. On a roof that has been worked on before, it is common to find one recently renewed piece next to three original ones, or vice versa.

When the building is protected and the existing lead is original. On a listed building or in a conservation area there is a positive reason to retain historic fabric where it can still do its job.

A patch is not a lesser repair when it is the right one. It is only a problem when it is being used to avoid a conversation.

When Patching Is False Economy

The test is age and condition of the rest.

If all four pieces went on at the same time, they have had the same weather, the same thermal cycling and the same number of frosts. When one gives up, the others are not far behind - and you will be paying for access again to deal with each one as it goes.

That access point is the whole argument. Getting safely to a chimney is a substantial part of what chimney work costs, and it is the same cost whether you are renewing one piece or all four. Three separate visits over five years costs considerably more than one visit doing the lot.

The other false economy is patching lead that failed because it was wrong from the start - too long a sheet, no laps, a cement fillet instead of a flashing, sealant over a chase. Renewing one piece to the same wrong specification produces the same failure again.

The Heswall Version of This

The houses here are large, much extended and built on a slope, which means most of them have several junctions rather than one chimney.

An abutment where a two-storey extension meets the main roof. A valley between two slopes. A saddle where a ridge runs into a wall. A back gutter behind a wide stack. A dormer cheek. Every one of them is leadwork, every one of them has a life, and most of them went in at the same time as each other.

So the sensible question on a roof like this is not "should I renew this flashing" but "what else is up there of the same age, and what would it cost to do it while the access is arranged".

It is also worth being told which junctions are sound. A roofer who comes down and says the abutment needs doing but the valley has fifteen years left in it is giving you something to plan with.

What to Ask For

A condition report on all the leadwork on the roof, not just the piece that leaked. That is a specific request and it is reasonable.

A price for the failed piece and a price for the lot, so the access saving is visible rather than assumed.

Confirmation of the lead codes being used and that pieces will be correctly sized with lapped joints - because the commonest reason new lead fails early is being made in lengths that are too long.

And, if anybody proposes a cement fillet or a sealant bead anywhere in the answer, a different quotation.