The short answer
You can buy lead and fix it, but good flashing depends on dressing, lapping and fixing the metal so water cannot get behind it and thermal movement cannot tear it. Mistakes show up months later as leaks. Work at height adds its own risk, so for anything above a ground-floor lean-to, a roofer is the safer choice.
Why it looks easy and is not
Lead is soft. You can bend it with your hands, and a roll of it from a builders' merchant feels forgiving. That is the trap. The softness that makes it easy to shape is the same quality that makes it creep, stretch and split if it is fixed wrongly.
A flashing has three jobs. It has to bridge the gap between a roof slope and a wall or stack, shed water outwards onto the tiles or slates, and stay free to expand and contract with the temperature. A strip of lead nailed hard at both ends cannot do the third job, so it tears itself apart over a few seasons.
The craft lies in the detail: the width of each lap, how the top edge is turned into a groove raked out of the mortar, the clips that hold the lower edge down, the folds at corners. None of these is obvious from a quick video, and each affects whether the roof stays dry. Our leadwork explained guide describes the main components if you want to understand the parts before talking to a roofer.
Tools and skills that matter
Working lead properly needs more than a hammer. A fitter uses a bossing stick and a dresser to shape the metal into corners, a lead knife, a chasing wedge, a bolster to open mortar joints and often a grinder with a dust-extracting guard to cut the chase. The metal must also be the right thickness for the job, which is set by the lead code. Code 4 is a common general choice and Code 5 is used where more strength is wanted, as the sheet-weight and thickness figures in the lead flashing wedges page indicate.
Wedges, or lead wedges, hold the top edge in its chase while the pointing is made. Without them, the lead can slump, and the mortar will not grip. They are a small item that makes a large difference, which is why that page exists.
Experience also tells a fitter when a plan is not going to work.
A fitter learns to read the building before touching the metal. They notice a chimney that leans, pointing that sounds hollow when tapped, a slope where the battens are rotten, or an old flashing that has been hiding a different fault for years. Fixing lead onto a weak base only buries the problem under new metal. The skill is in the decisions made before the first cut, and it comes from years of seeing how these details age: a crumbling chase, a stack that moves, a wall that is damp behind the bricks. A beginner finds out later, usually when the first wet winter arrives.
The mistakes that cause leaks
Common faults are easy to list. Laps that are too short let wind-driven rain creep back. Fixings that pierce the exposed face let water in at each nail. A bead of sealant standing in for a proper groove fails when it dries and shrinks. Lead laid directly onto some timbers or fresh mortar can be attacked by the alkali, so a separating layer is needed. A flashing that is too long between joints will buckle when it expands.
Another mistake is to cover a leak, not trace it. Water at a chimney can come from a cracked stack, loose pointing or a failed valley further up the slope, and fresh lead over the wrong cause hides the real fault until the ceiling stains again.
For smaller repairs, the page on lead flashing repairs sets out which problems are a quick job and which need the metal replaced.
Safety at height, and with the metal itself
The greater danger in a DIY flashing job is the fall, not the lead. Chimney stacks rise from the highest point of the roof, and a tiled slope with moss or damp is slippery. Working from a ladder against a roof edge, with a heavy tool in one hand, is a poor position. Proper work at height uses a scaffold or a tower with edge protection.
Lead is also a toxic metal. Handle it with clean gloves, never eat or smoke while working, wash your hands afterwards and keep offcuts away from children and pets. Take particular care if you cut or grind old lead, which makes fine dust. Do not burn or heat lead without training, because fumes are harmful. Our page on whether lead roofing is safe explains handling in more detail.
Welded lead, which is a different skill again, is covered on the lead welding page and is not a DIY task.
When it is sensible to call a roofer
A tiny cosmetic job on a ground-level porch is one thing. Chimneys, parapet gutters, valleys and anywhere above a first-floor window are another. If you can see the flashing only from a ladder, or you are not sure why it is leaking, leave it to a roofer who can find the cause and fix it once.
Parapet and box gutters are a good example of a detail that looks like a simple trough. They need the right falls, upstands and expansion joints, and a fault can run water into the building. Our page on lead parapet gutters sets out what they involve.
If you would like a second opinion before you buy materials, we will visit, photograph the flashing and give you a written quote after the survey. Our price is for the job as a whole, and the finished work carries a 10-year workmanship guarantee, put in writing. See lead roofing for the full range.