Picture a small box standing on a roof slope, with a window in its front, a roof over its head and a wall at each side. Those side walls are the cheeks. The roof is the top. Lead is the usual cladding for both, because it can be dressed round awkward corners, joined to the main roof without a visible seam and left to weather for decades. Where the box meets the slope there is also a ring of flashings (strips of metal bridging a joint between two surfaces) and soakers (small folded lead pieces interleaved with slates or tiles).
This guide is about the dormer alone: how the cheeks and top are clad, which faults we meet and what renewal means. The wider story of lead flat roofs on period houses covers bays and larger roofs, so we keep to the small scale here. For the whole service, start at our lead roofing page.
Reading a dormer from the lane: cheek, top, sill and back
Stand below a dormer on a Stroud terrace and you are looking at four areas of waterproofing that meet at corners. Naming them makes the faults easier to follow.
The cheeks
The side walls have a timber frame with boarding over it. The cladding may be lead, render, tile hanging or timber, and lead is the one that demands an understanding of how metal moves. Each cheek is a near-vertical face, so the lead is hung rather than laid.
The top
The roof over the window may be pitched, hipped, curved or flat. A flat top is boarded, covered in a separating layer and clad in lead in bays divided by rolls and drips. A pitched top is more often slate or tile, with lead only at the ridge, the edges and the joint with the main roof.
The sill and the front
Below the window sits a sill, and below that an apron of lead dressed over the front edge of the dormer and lapped onto the main roof covering.
The back
Behind the dormer, a back gutter or abutment flashing collects the water that runs down the slope above. It takes the full flow and sits partly out of sight, which is why we look at it first on any leaking dormer.
How lead cheeks are clad
Cladding a cheek is not the same job as laying a roof. Lead is heavy, and on a vertical face it creeps slowly downward under its own weight. It also expands and contracts with temperature. So the cheek is divided into short pieces, each held at the top and free to move at the sides and bottom.
Panels and seams
Panels are joined with a welt or a lapped seam rather than solder, so each one can shift without tearing. MyJobQuote notes that flashing lead is correctly fitted in lengths of about 1.5 metres, and the same logic of short, free-moving sheets runs through cheek work.
Fixing at the head
Each panel is anchored along its upper edge with a few clips or a fixing strip hidden in a fold. Nails through the face of the sheet are a fault, not a method, because they hold the lead rigid until it tears.
Which code
Royston Lead's cast sheet brochure lists dormers among the uses for Codes 4 to 8, and Leadworx describes Code 4 as the everyday choice for flashings. A large or exposed cheek may call for a heavier code, and we state the choice in the quote rather than treating it as a default. Our lead codes guide explains the table in full.
The lower edge
At the foot of each cheek the lead dresses down over the main roof covering, meeting stepped flashings or soakers that run up the slope. The overlap has to be wide enough to shed water away from the joint, and the lead must lie flat on the slates so wind cannot lift it.
The dormer top: falls, rolls and the apron at the front
A flat or low-pitched dormer top is a small lead roof, and it needs enough fall to drain. BS 6229, as reported by Rockwool, says to design the deck to 1:40 so that, after tolerances, it still finishes at 1:80. On a top only a metre or two across there is little room to correct a dip once the boards are down.
Boards and separating layer
Lead is laid over a separating layer, a thin fleece that stops it rubbing on the boards and absorbs small movements. The boards must be dry, flat and free of proud nail heads. A sagging deck gives ponding, and standing water shortens the life of a lead covering.
Rolls and drips
A top wide enough for more than one sheet is divided into bays by wood rolls, rounded battens that the lead is dressed over. Where the fall runs any distance, a drip, a small step in the deck, breaks the run so the lead never sits in one long sheet. Our guide to lead flat roofs explains why, and the same principles apply here in miniature.
The front edge
At the front, the lead turns over a drip batten or fascia and lets water fall clear. Lead pinched too tight at this edge, or finished without a drip, sends water back along the underside and rots the timber behind.
A failed lead dormer top is often a deck problem as much as a lead problem. If the boards underneath have gone soft, new lead alone will not last.
Faults we find on lead dormers
Dormer leaks are among the first jobs people call about after a wet spell, and the cause is nearly always on a short list. We photograph each fault on your own roof so you can see what we mean.
Slumped or torn cheeks
Where a cheek has crept, the sheet has sagged away from its fixing and the lower part bags out. The metal then thins and tears at a fold. From below the cheek looks wavy, with seams opened up.
Splits at the corners
A corner has to be folded in two directions at once. If it is dressed too tightly, or fixed rigidly to both faces, it cracks at the fold after repeated movement. A split corner is a symptom of the detail, not simply of age.
Open joints at the window
The line where lead meets the window frame or masonry is often sealed with mortar or mastic. Both shrink and crack well before the lead does, and water enters through the gap and shows as a damp patch on the inside reveal.
A blocked back gutter
Leaves and moss build up in the channel behind the dormer, and water backs up under the main covering. The mark shows on the ceiling under the dormer, a long way from the real entry point.
Rotten timber behind
If water has been entering for a while, the cheek frame and boarding can be soft. We probe the timbers at the survey, because renewed lead over a frame that cannot hold fixings is wasted money.
Missing lead
Lead is valuable, and dormer leadwork can be stripped. Our lead theft guide covers what to do next.
Patching a dormer or renewing it
Not every leaking dormer needs stripping. A torn panel, one cracked corner or a perished sealant line can often be repaired locally, with the old lead cleaned back and new lead let in. The test is what lies behind. If the surrounding lead is thin and the fixings are failing along a whole face, a patch buys little time.
What a full renewal involves
Renewal begins with access. MyBuilder gives about £1,125 as a typical scaffold figure for a full re-roof, and one dormer may need only a tower or a short run of scaffold, priced on the survey. Then the old lead is lifted, the timbers are checked, any soft boarding is cut out and new boards go in, then the separating layer is laid. The new cheeks and top are cut and fixed, the flashings are tied back into the main roof, and every edge is checked for fall and for anything loose.
Costs, nationally
For orientation, MyBuilder's 2026 flat roof guide puts lead flat roof covering at £150 to £200 or more per m². Checkatrade's repair cost guide, updated October 2026, gives lead flashing repairs at £50 to £70 per metre and stepped flashing at £80 to £120 per metre in Code 5, excluding VAT. Treat them as national figures from other firms' surveys, not as what we charge. Access, the number of faces and the state of the timber change a dormer job a great deal, so we price each element separately once we have seen the dormer. For more on flashing prices, see our lead flashing cost page.
On lifespan, MyJobQuote reports that lead flashing that is fitted correctly may last more than 80 years, and Less gives 50 to 100 years for lead flat roofs. Both are typical ranges, not promises, and workmanship and upkeep decide where a dormer lands in them.
Listed houses, conservation areas and building a new dormer
Replacing worn lead on an existing dormer with the same metal in the same pattern is repair, and does not usually need planning permission. A listed house is different: Stroud District Council says Grade II and Grade I alike carry full legal protection, so changing the character of the leadwork can need consent. Our guide to leadwork on listed buildings goes through that.
Adding a dormer
Dormers are covered by Class B in the permitted development rules, and Class B falls away on Article 2(3) land. That land includes conservation areas and the Cotswolds National Landscape (formerly the AONB). Stroud District has 41 conservation areas, and just over 50% of the district lies within the National Landscape. A new dormer in those places needs a planning application, so speak to the planning team first.
Building Regulations
A new dormer also needs Building Regulations approval, because it alters the structure. Re-covering an existing dormer sits inside the Planning Portal thresholds: less than 25 per cent of the building envelope and less than 50 per cent of the roof affected, with no covering 15 per cent or more heavier. Should the job be notifiable, we tell building control for you; in Stroud District that body for Stroud District is the Gloucestershire Building Control Partnership.
Bats and birds
A dormer roof void can shelter bats or nesting birds, both protected. If we see signs, you will hear before any lead comes off.
Sending us a dormer to look at
The visit is a survey, and it includes a close look at the dormer from a ladder or scaffold, not only from the ground. We record the cheeks, top, sill and back gutter, probe timber where we can reach it and check the inside for stains. You get photographs of your own dormer with a note against each fault.
If lead work is needed, the quote comes in writing with scaffold, stripping, boards, lead and its code, labour, waste and making good each priced separately. We match like for like on an older property, so lead stays lead and the existing pattern of rolls, drips and seams is followed. On completion nothing is left behind on site, and the work carries a 10-year workmanship guarantee, in writing.
Ring 01453 933613, WhatsApp and the enquiry form both work, with a photograph of the dormer and a line on where water shows inside. If the dormer sits beside a bay or porch, those details are often linked, and our guide to lead bay and porch roofs covers the neighbouring questions.