The short answer
A lead flat roof can usually be repaired. Small splits and open seams are welded shut by lead burning or covered with a lead patch dressed and fixed properly. When the lead is cracked across many bays, worn thin, or the falls hold standing water, patching only moves the leak along, and a re-cover is the sounder answer.
Why lead flat roofs split
Lead is long lived, but it moves. On a sunny day a bay of lead on a flat roof grows slightly longer, and on a cold night it shrinks back. Each cycle works the metal a little. If the bays are laid too large, if the sheet is fixed too rigidly, or if it was never allowed to slide on its underlay, the stress builds in the same places and eventually the lead cracks, usually along a fold, a joint or a corner.
Other causes are more everyday. Someone walks across the roof with hard soles and dents the sheet. A gutter or outlet blocks, and standing water sits on the lead. A nail or screw from a past repair makes a hole. Leaves and moss hold damp against the metal. Our page on lead white staining covers the powdery surface that lead builds up outdoors, which is a surface finish and not in itself a fault.
Lead burning, patches and what each can mend
Lead burning is the trade's name for welding lead. The roofer melts a thin strip of lead into a seam or crack using a gas flame, so the edges fuse into one piece with no sealant involved. Done properly, it makes a joint as strong as the sheet around it. Our page on lead welding goes into the method.
A patch is different. A piece of new lead is cut to size, dressed over the damaged area and fixed so water runs over its edges and not beneath them. Patches suit a localised split or a hole from an old fixing. Neither method helps if the sheet around the damage is brittle or thin, because the next crack opens a few inches away. Before repairing, the roofer checks the lead nearby, the underlay and the boards. Wet or rotten decking under the metal needs to be dealt with first.
Foot traffic and day-to-day care of a lead roof
Lead is soft. A roof used as a terrace, a place to store paving slabs, or a route for a satellite engineer with hard boots can be dented and pinched until it splits. If people need to cross it regularly, duckboards or timber walkways spread the load and keep the lead clean. Heavy objects and sharp ones stay off.
Care is mostly about drainage. Keep outlets clear, take off leaves after autumn, and look for puddles that last. Moss on lead is less common than on tiles, but debris in a corner will hold damp against the sheet. None of this needs anyone on the roof if the access is by a proper hatch or a scaffold, and a quick look from an upstairs window shows plenty. The rest of our lead roofing pages cover the individual details of a lead roof in turn.
Falls, drainage and why water stands
A flat roof is meant to shed water. IKO's guidance, citing BS 6229:2018, sets the finished minimum at 1:80, and adds that a roof should be designed to 1:40 so building tolerances do not eat into it. If water stands on your roof for days after rain, a loss of fall may have developed through sagging boards or a deflected joist, and the lead will keep suffering until that is dealt with.
Look at the outlets as well. A blocked outlet, a sunken gutter or a downpipe that backs up all leave water sitting on the metal. Clearing and refixing outlets is a small job and is often the first step. Where the fall itself is poor, a repair in the lead alone does not cure the cause, and the sensible plan is to correct the structure when the roof is next opened up.
When stripping and starting again makes sense
Re-covering means stripping the lead off the roof and laying new sheet, usually with new underlay and repairs to the decking. It is the right call where cracks run through many bays, where the metal has thinned, or where repeated patches have turned the roof into a patchwork. Lead is a long-lasting covering: Less gives 50 to 100 years for a lead flat roof, so a roof that fails much earlier usually had a problem in the original design.
A re-cover can bring Building Regulations questions. Under Approved Document L, replacing the waterproof layer of a flat roof counts towards renovation of a thermal element, and the council's building control team or a registered building control approver says what applies to your roof. Roofs on older and listed buildings carry extra rules, which our page on leadwork on listed buildings explains. Zinc is sometimes proposed as a lighter alternative, and lead against zinc compares them.
What it costs and what we will ask to see
MyBuilder's flat roof guide, updated in August 2026, gives lead at £150 to £200 or more per square metre for a replacement covering. That is a national typical figure, and the amount of repair on your roof is far smaller than a full re-cover. A repair is priced on how many cracks need mending, how easily the roof can be reached and whether any decking needs attention.
The survey photographs show the lead bay by bay, the seams, the outlets and the edges. A written quote then sets out what we propose, and if a repair is enough, a full re-cover is not what we will propose. Faults in our workmanship are covered for ten years, a promise we put in writing. Ring 01793 626096 or message us on WhatsApp.