Question answered
What are lead soakers?
The short answer
A lead soaker is a hand-bent piece of lead that slips beneath the tiles or slates along the side of a chimney or a gable wall. One leg lies flat beneath the covering and the other turns up the wall, where the flashing overlaps it. There is one soaker for each course of tiles, and together they carry water out over the roof. They are cut from code 3 lead.
A soaker is one of the least visible parts of a roof and one of the most important at a wall. Here is where it sits, the job it does and how it ends up giving trouble.
Where a soaker sits on the roof
Wherever a sloping roof stops against a vertical wall, such as a gable, a chimney or the side of a dormer, there is a gap along the junction. The covering cannot simply butt up to the brickwork. That junction is called an abutment, and soakers are the traditional way of making it watertight on tiled and slated roofs.
Each soaker is a rectangle of lead folded down its length. One half is slid under the tile or slate at the roof edge, and the other half stands up against the wall. Because every course has its own soaker, water that reaches the wall is turned back out onto the course below, and then onto the next, until it reaches the gutter.
The step flashing, or the cover flashing in a continuous strip, is dressed over the top of the upright leg and tucked into the wall joint. Soaker and flashing work as a pair, and you rarely see the soakers at all.
Why there is one for every course
Tiles and slates overlap each other in rows. A strip of lead running the full length of the wall would sit on top of the tiles and leave their lower edges unsealed. A separate soaker for each course follows the overlap, so the lead sheds water in step with the covering.
That is why the job suits plain tiles and slates, which are small units laid in overlapping rows. Larger profiled tiles often meet the wall with a continuous lead apron or a different arrangement, because a soaker for each course would not follow the shape of the tile.
The look from the ground is a series of small steps in lead up the wall, or a single sloping strip with stepped cuts in it. What is underneath it is the part that fails quietly, and we check it from inside the loft as well as the outside.
The lead code that suits a soaker
Royston describes code 3 lead as recommended for soakers only. It is 1.32 mm thick and weighs 14.97 kg/m². The weight is enough for a piece that is hidden, held down by the covering and bent just once. It is not recommended for the exposed flashing above, which is normally code 4. Our answer on which lead code is used for flashing sets out the weights side by side.
Soakers are cut to size for the tile or slate. Their length decides how far they sit under the covering, so the cutting must match the lap of the tile, and a soaker that is too short leaves a path for water. A fitter who sets them out with the tiles gets the overlap right the first time.
The grey of aged soakers is the same lead patina you see on any old flashing, and it belongs there. Where a roof has been re-covered in a different tile, old soakers sometimes no longer suit the new lap and are left in place, which is worth checking.
How soakers go wrong
Because soakers are hidden, problems show up as stains on a chimney breast or a damp patch beside a gable wall rather than as a visible fault on the roof. The usual causes are physical. A soaker can slip down if the tile above it was lifted and re-laid, or if the holding nail has gone. A soaker can be missed altogether when a roof was patched in a hurry and the tile was bedded in mortar against the wall.
Often the soakers are fine and the problem is above them. If the flashing has come away from the wall joint, rain gets behind it and runs onto the soakers faster than they can shed it. Our page on lead flashing pulling out of the wall covers that fault.
A white powder on the lead is just a surface patina and not a failed soaker.
Renewing soakers, and what it involves
To renew a soaker, the tiles or slates along the wall have to be lifted so the new lead can be slid in under each course. The edge strip is then re-laid, and the flashing is dressed over the top. Where the covering is brittle, some pieces can break on lifting, so the survey allows for spare tiles or slates.
Often a flashing repair alone will not reach the real fault, because a failed soaker is under the covering. So we trace the leak from inside first and photograph both what we find and what we propose. Lead flashing repairs has more on the different repairs.
When the survey has been done, our written price covers the entire job in a single sum. A leak that is letting water in gets made safe before anything else. The wider range of lead work is on our lead roofing page.
Soakers: two more questions
Can a soaker be renewed without stripping the whole roof slope?
Usually the covering along the wall is lifted, not the whole slope, because soakers sit at the edge. How far in depends on the tile and its condition. Old slates and tiles can crack when moved, which is allowed for when the work is planned.
Why would a damp wall be blamed on soakers if the flashing looks sound?
A flashing can look neat from the ground while the soaker beneath has slipped or been left out. Water follows the gap, not the visible lead. Checking from inside the loft against the wall shows where it has actually been running.
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