Question answered
Can a lead flat roof be repaired?
The short answer
A lead flat roof can usually be repaired if the lead is still sound around the fault. A split or hole can be patched or welded, and a lifted seam can be reworked. Where cracking runs through many sheets, or the deck beneath is wet or sagging, relaying the roof is the sounder repair and usually the better value.
Yes, in many cases. Lead is a repairable material, and a roof with a few splits is a very different problem from one where the sheets have failed along their length.
Why lead roofs crack in the first place
Lead is soft, heavy and never still as it warms and cools. When a sheet is laid too large, or fixed so firmly that it cannot slide, the movement has nowhere to go and the metal eventually splits. This is fatigue, and it often begins at a fold, a fixing or a corner.
Other causes include damage from foot traffic on thin lead, a sagging deck that lets water pond and wear at the surface, and nails or clips used in the wrong place. Theft is its own subject, covered on our lead theft page.
Finding the cause matters, because patching a split without dealing with why it happened simply moves the failure a few inches along. The choice of repair rests on three points: how big the sheets are, how they are fixed and what the deck under them is doing.
Patches and welded repairs
A small hole or split in otherwise sound lead can take a lead patch, dressed over the fault and held in a way that leaves the sheet free to shift. Where a stretch has failed, it can be cut away and a fresh piece welded or soldered in, which joins the metal itself and not just a seam on top of it.
A welded repair is neat and durable if the surrounding lead is in good condition. It suits small areas, in dry weather, with the surface cleaned back to bright metal first. The repair is only as sound as the sheet it joins, so a weld into thin or cracked lead tends to fail beside the weld.
Sealant or bitumen smeared over a split is a different thing. It may quieten a drip for a time, yet it conceals the fault; does lead flashing sealant work covers why.
Rolls, drips and seams that have lifted
Many lead roof leaks sit at the joints and not in the middle of a sheet, which is good news for the cost. A roll is a raised joint running with the fall, and a drip is a step across it; both are there to let the lead move. If a roll has been crushed, or a drip is too low, water can be forced under it.
Those details can often be reworked: the roll opened, the lead reshaped and closed again, or the drip rebuilt with a taller step, with the neighbouring bays left alone. Reworking is a fraction of the cost of new lead when the sheets themselves are sound. The reasons for these joints are laid out in rolls and drips on a lead roof.
Flat-roof guidance from IKO, citing the 2018 edition of BS 6229 (since revised), gives 1:80 as the finished minimum fall, with a design fall of 1:40. If water ponds against a seam because the fall is poor, a patch cannot correct it.
When to relay instead
Relaying means stripping the lead, checking and repairing the deck, correcting the falls, and laying new lead in correctly sized bays. It is the right answer when cracks are widespread, when the lead is badly worn thin, or when the deck is rotten or wet underneath.
It costs more up front, but it resets the roof. Less gives a lead flat roof a typical life of 50 to 100 years, and MyBuilder puts lead at £150 to £200 or more per m² for a flat roof. Both are typical national figures from guides, so treat them as context rather than a price for your roof.
Renewing a flat roof can also bring Building Regulations into play. Approved Document L lists replacing the waterproof membrane among the ways a thermal element is renovated, and once the thresholds are passed, extra insulation could be required as well. We explain what applies and notify building control where the work requires it. For how long a lead roof is expected to last, see lead roof lifespan.
How we assess it and what you get
We walk the roof and study the lead, the joints, the upstands and the deck. Where the roof can be reached from inside, we inspect the underside for damp and staining. Photographs show you the same view, and the written quote that arrives afterwards is a single total.
Repair is the choice wherever it will hold, and the survey tells you plainly when it will not. A weld over rotten timber is not a repair, and relaying a roof that needs only a patch is poor value, so the deck gets probed as well as the lead.
Access can add to the total, particularly if a scaffold is needed for a roof above a pavement or a high parapet. Ask whether each figure covers scaffolding and VAT. For leadwork at a chimney, what chimney leadwork costs gives typical UK ranges, and the rest of the topic sits under lead roofing.
Lead flat roof repairs: two more questions
Is it cheaper to patch lead or to cover it with another membrane?
A patch is cheaper for a small fault. Covering lead with another membrane hides the problem and can trap moisture on a deck that is already wet. If the lead has failed widely, relaying it in lead, or stripping and replacing it with another system, is the better route.
Can a leak through a lead roof come from somewhere other than the lead?
Yes. Water can enter at an upstand, a parapet coping, a rooflight kerb or a failed outlet and show up elsewhere. Following the marks from inside and then checking outdoors places the entry point before any repair is priced.
Tell us about your roof
Describe what is happening and we will call you back to arrange a visit.
- Photographs of what we find
- A written quote with one total price
- Or call 01903 299063
10-year workmanship guarantee, in writing.