Last updated: August 2026
Ask an experienced roofer where a Victorian or Georgian roof leaks and they will point at the lead before the slate. The valleys, the flashing at the stacks and the abutments, and the parapet linings are all lead, and it is the lead that most often lets go first.
Why Lead Is the Heart of a Period Roof
On a period roof, lead does all the difficult work. It lines the valleys where two slopes meet, it flashes the joint where the slate meets a chimney stack or a wall, it dresses the parapets, and it seals every abutment the slate cannot cover on its own. Slate sheds water off the open roof, but every junction, every change of direction and every upstand relies on lead. Get the lead right and the roof stays dry for generations; get it wrong and it leaks no matter how good the slate is.
That is why we treat the lead as a craft in its own right rather than an afterthought. On a restoration the lead work is often the larger and more skilled part of the job, and it is the part a general roofer most often gets wrong.
How Old Lead Fails, and Why Mastic Is Not the Answer
Lead expands and contracts with every warm day and cold night, and over decades that movement tells. Lead that was laid in lengths that are too long cracks along the line where it has been forced to move too far. Joints open, old lead work thins and splits, and previous repairs done in mastic or bitumen perish, lift and let water straight past. A bituminous patch over a cracked valley is the classic false economy: it looks like a fix for a season, then fails and often takes the surrounding slate with it.
How Lead Work Is Done Right
Proper lead work means the right code of lead for the job, laid in the correct lengths so it can move without cracking, dressed and bossed to shape by hand rather than sealed with mastic, and welted and lapped at the joints the traditional way. A valley is formed so it carries the water cleanly to the outlet; flashing at a stack is stepped into the brickwork and dressed down over the slate; a parapet is capped and lined so nothing tracks behind it. Done this way, the lead outlasts almost everything else on the roof.
If your roof has cracked or patched lead at the valleys, stacks or parapets, a free inspection will tell you what needs renewing and give you a written price for doing it properly.
