Lead flashing and leadwork in Bury St Edmunds, Ely and Thetford

How lead flashing and leadwork works

Leadwork is where most roofs actually leak, and it is the part most often bodged. Lead has to be cut into the mortar joint, wedged, and left free to move, because it expands and contracts more than anything around it. Sealed rigidly, or run in lengths that are too long, it splits along the fold within a few years.

If you can see mastic or sand and cement along a flashing line, someone has covered a problem rather than fixed it. Those repairs shed water for a season or two, then trap it behind the covering, and the damage underneath is always worse than it would have been. Cutting it out and redressing it properly is the only permanent answer.

Code matters. Code 3 is too thin for most abutments and it fatigues. Code 4 is the normal domestic choice for flashings and soakers, code 5 for valleys, back gutters and anything that carries water rather than just shedding it. It is not an upsell, it is the difference between a detail that lasts thirty years and one that lasts five.

Chimney flashings are four separate details, not one. Soakers interleaved with the tiles up each side, stepped cover flashings chased into the brick joints over the top of them, an apron across the front and a back gutter behind. Skip any one of them and the stack leaks, which is why a stack sealed all round with mortar is a stack that will leak.

Patination oil is not cosmetic. New lead left untreated reacts with rain and runs a white carbonate stain down whatever is underneath it, which on a rendered or light brick elevation is very visible and hard to remove. Wiping new lead with patination oil at the end takes minutes and prevents it entirely.

What the job includes

• Old flashing and any previous mastic or cement repair cut out
• New chase cut into the mortar joint, not into the face of the brick
• Code 4 or code 5 lead as the detail requires, in correct lengths
• Soakers interleaved with the tiles or slates where the roof meets a wall
• Back gutters and cover flashings to the upper side of a chimney
• Valley linings replaced with proper laps and clips
• Lead wedged and pointed in, then patinated

Signs you need it looking at

• Damp on a chimney breast or where a roof meets a wall
• Mastic or cement visible along a flashing line
• Lead lifted, rippled or peeled away from the brickwork
• Staining in the loft directly below a valley
• Water coming in on one side of a stack only