The short answer
It is possible, but it is a skilled job with real risks. Replacing lead flashing means working at height, cutting a chase into brickwork, forming lead to the wall and tying it in with the roof covering. Flashing stuck on with sealant will fail again. If you are not confident on a roof, have a roofer do it.
What the job involves
New flashing is more than a strip of lead. A proper job has several stages, each one dependent on the last.
- Stripping the old lead and any loose pointing, and checking the brickwork and roof covering beneath.
- Cutting or re-cutting the chase, the groove in the wall that takes the top edge.
- Choosing the lead code, and cutting and bending the sheet to the shape of the roof and wall.
- Fitting soakers where a roof rises against a wall, and a cover flashing over them.
- Wedging the lead into the chase and clipping the lower edge.
- Pointing the chase once the lead is in.
Each stage has judgement in it. A chase cut too shallow will not hold a wedge. A flashing bent too tight will split. A cover flashing laid without soakers will leak the first time the pointing opens. Our page on how lead flashing is fixed describes the method.
You also need the right tools and the right lead. Royston Lead's brochure lists Codes 4 to 6 for flashings and Codes 3 and 4 for soakers, so a single sheet bought off a shelf may not suit every part of the junction.
Working at height
The greater risk is not the lead but the height. Falls from roofs and ladders injure people seriously, and the Health and Safety Executive (HSE) publishes guidance on working at height. A chimney or wall flashing usually stands on the roof edge or high on a slope, where the risk peaks.
A ladder alone does not make a roof safe to work on. Flashing work calls for a stable platform or scaffold, a way to stop materials and tools falling and a second person on the ground. Wet, frosty or windy conditions make everything worse.
Hiring someone makes you a domestic client under CDM 2015, the construction safety regulations. That label covers a homeowner whose house is the site. HSE guidance expects a construction phase plan even from a single contractor working alone, with extra appointments once a second contractor joins.
Do not climb a roof alone, and do not stretch from a ladder to reach a chimney. If water is already getting in, a roofer's temporary cover is a safer first step than any attempt at a permanent fix.
Why sealant fixes fail
The usual DIY approach is a tube of sealant run along the joint, and it is understandable. It is cheap, quick and can be done from a short ladder. Yet it rarely lasts.
The problem is movement. Roofs and walls expand and contract as they warm and cool, and the gap between them opens and closes. Sealant bonded to both surfaces is pulled until it tears away from one of them, which reopens the gap. It also ages in sunlight and weather faster than the metal and brick around it.
It does a second kind of harm too. A thick bead can hide what is underneath, so a failing flashing is covered up and the damage behind it carries on unseen. By the time a stain shows through, there may be rot in the timber. Our page on sealant on lead flashing weighs up the cases where it has a place.
Self-adhesive flashing tape has the same limitation. It sticks to what is clean, dry and still, and a joint that moves will pull it away.
A proper repair holds the lead mechanically and lets it move, which is the opposite of gluing it down.
Wildlife, and when to call a roofer
One more point is easily missed: bats. On GOV.UK, roof repair and replacement appear in the list of work that can harm them, and the guidance says the species and their roosts are protected. Blocking access to a roost is covered by the Wildlife and Countryside Act 1981 where it is intentional or reckless, and the Habitats Regulations 2017 reach damage to a roost even without any intent. If you see bats, or droppings under a flashing, stop and take advice.
Call a roofer if the job is high, if the lead is split across a wide area, if the chimney or wall itself is crumbling, or if the source of the leak is a mystery. A first-time DIY attempt on a flashing is hard to get right.
If the fault is small and the roof is low, for example a short flashing over a ground-floor extension, you may still prefer to send us a photograph. We survey the junction, show you what the problem is and send a single written total. The lead flashing repair page describes what we do, and the lead roofing hub covers the rest.
