What are lead wedges for?

When a flashing is turned into brickwork, its top edge goes into a slot. On its own, that edge would drop back out as soon as the work was left, and the lead would hang open at the wall. A wedge is a small strip of lead, folded or rolled, that is tapped into the slot beside the flashing so it grips the lead against the brick or stone.

Once wedges are in at intervals along the length, the flashing stays where it was put. The mortar or sealant that goes in afterwards then does its proper job, which is to shut out water, not to carry the weight of the lead. That division of work is the point. A flashing held only by pointing will drop when the pointing cracks, and pointing on an exposed wall does crack in time. Wedges are cheap, quick to fit and invisible once the joint is filled, which is why their absence is only noticed later.

Wedges are used wherever lead is turned into a masonry joint: the top of an apron on a chimney, a stepped flashing running up a gable wall, the cover flashing above a lean-to roof, or the upper edge of a flashing at a conservatory wall. Wherever lead is fixed into a joint, a wedge is part of the normal method.

They are not needed on lead that is nailed or screwed to timber, or on lead held along a lower edge. Those use other fixings, which our answer on lead clips covers. For the flashing that depends most on wedges, see our page on the lead apron flashing. A stone wall, a brick wall and a rendered wall each ask for a slightly different approach to the chase, but the principle of wedging first stays the same on all three. Where a chimney has been rendered, the render may need cutting back so the flashing can sit in the brick behind it.

The mortar joint is raked out to a clean slot, brushed free of dust and checked for loose pieces. The lead's folded top edge is then pushed in and wedged at close intervals, with each wedge tapped home until the lead is tight. Only after that is the joint filled, either with mortar or with a sealant in a joint that suits it.

Which filler to use is a separate question, and what suits one wall can fail on another, depending on the stone and how exposed it is. We cover it in our guide to mortar or sealant for lead flashings. What does not change is the order: wedge first, fill second. A neat line of pointing with no wedges behind it is a flashing waiting to drop. Raking out too deep, or into a joint that is itself crumbling, weakens the hold, so the condition of the brickwork matters as well.

From the ground, a flashing with no wedges may look fine until the pointing starts to crumble. After that the lead sags forward at the top, a dark gap shows along the joint, and rain can run in behind it. Look for lead whose back edge you can see, lead that moves when pressed, or a trail of old sealant along the top.

Inside the house, the clue is damp near the wall or chimney breast, often after driving rain. When a flashing is held only by filler, one cold winter or a few hard gusts can be enough to loosen it. The fix is to rake out, refix the lead with wedges and point it again. We trace the water before suggesting any repair, so you are not paying to fix a joint that was never the source of the leak. Photographs of the gap, taken from the loft or a ladder, tell the story better than a description, and they go in the survey.

You can ask a simple question: are the lead flashings wedged into the joint before they are pointed? A roofer who does the job properly will answer at once. If the reply is that sealant is used instead of wedges, ask why, and ask what holds the lead in place before the sealant cures.

Wedging adds little to the price of a job, while leaving it out can mean taking the whole flashing down again. It is part of a proper job, and the quote, in writing with one total price, covers the whole method. If you want to see the work, ask for photographs of the chase before it is filled. The lead roofing and leadwork page lists the lead jobs we take on. It is also fair to ask who will be on the roof, how the chase will be cut, and what is done about weather while the joint is open, since an open chase in rain lets water into the wall. A tidy answer to all three shows care.