Why is my lead flashing leaking?

Flashing is the name for the metal that links a roof to whatever rises out of it: a chimney, a side wall, a dormer cheek or a parapet. Lead gets chosen because it can be bent to the shape of the junction and dressed down tight. Its lower edge rests on top of the roof covering. Its upper edge is tucked into a slot raked out of the brickwork, known as a chase, or under the wall's cladding.

Leaks start at those two edges and at the joints between pieces. Wind can lift an edge that has no clips holding it down. A chase may have lost the mortar or sealant that closes it, so rain runs in behind the lead. A section may be cut too short to give a proper overlap, or a corner may have been folded badly and never sealed. Any of these can leave a brown mark on the wall or ceiling next to the junction, often after one particular kind of weather.

Start with a look from the garden or the pavement, using binoculars, long before any ladder comes into it. A clean split across the lead, a corner curling upwards or a gap between flashing and wall tells you where to start. Cracks often follow the way lead moves with temperature, which our answer on why lead cracks on a roof explains. A lifted edge may point to missing clips, the small lead strips that hold the lower edge down.

Please do not climb onto a roof to check. A fall costs far more than a leak. A roofer can photograph the junction close up and show you the fault before any work begins. If the lead is split but otherwise sound, a repair can hold. If it is thin, torn in several places or already patched more than once, renewing that section usually gives a longer result than patching a third time. Either way you see the pictures first and make the choice yourself, with the evidence on the table.

A tube of sealant run along a crack stops the water for a while. It does nothing about whatever opened the crack, and it conceals the fault from whoever looks next. Self-adhesive tape works as an emergency cover and has a place in a roofer's van, though our comparison of flashing tape against lead explains why it counts as a stopgap.

Check the pointing along the chase as well. If the mortar or sealant at the top edge has cracked or dropped out, water gets behind the lead however good the sheet is. Which material suits a given wall is covered in our answer on mortar or sealant for lead flashing. Repairs that deal with the cause tend to last. Repairs that only cover the symptom tend to come back at the next heavy rain, usually on a wet weekend when nobody can be found to fix them.

Water travels. A stain beside a chimney may start with a slipped tile above, a cracked chimney pot, a failed render band or a blocked gutter, then run along a timber before it appears on the ceiling. Renewing flashing that was never at fault wastes money, which is why we examine the whole junction first and photograph what we find.

The timing of the leak is a useful clue. If the stain appears only after driving rain from one direction, the cause is often an exposed joint on that side. If it appears after any rain at all, look higher up the roof. Tell us what you have noticed and when, and which room is affected, because that narrows the search a good deal. The survey then gives a plain verdict: repair, patch for now or renew, with a photograph of every fault, so what we describe is plain to see, and why we suggest the route we do.

Checkatrade's roof repair guide, updated in October 2026, lists lead flashing repairs at £50 to £70 per metre, with VAT on top. For a small patch at a chimney, MyJobQuote's September 2026 guide gives £150 to £250. Access shifts the figure: a flashing high on a stack costs more to reach than one on a low wall. The written quote that follows the visit shows a single total, and it names the lead code and the length of flashing involved so you know what is being renewed.

MyJobQuote gives a typical life of more than 80 years for lead flashing. Treat that as a general guide, never a guarantee for one roof. A leak early in a flashing's life suggests something went wrong in the fitting, and fixing that fault is what makes the repair worth paying for. For the full picture, see the lead roofing and leadwork hub.