If a leak is tracking down from a chimney, valley or dormer in North Walsham, failing lead work is the most likely cause.
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Lead flashing is the formed metalwork that seals the joints where a roof meets a vertical surface: chimneys, parapet walls, dormers, roof lights and valley gutters. When it is cut and dressed correctly, it flexes with the building through frost and heat without cracking. When it is rushed, poorly fitted, or simply old, water gets underneath and begins tracking into the roof structure, sometimes for months before a stain appears on a ceiling.
Every piece of lead we cut is formed on site to the exact profile of the masonry and roof covering. That means cutting proper stepped flashings into mortar joints, not just bedding a strip in mastic and hoping it holds. Mastic-only repairs can fail: the sealant shrinks, cracks, and lets water in again.
We carry out lead work on chimneys, valley gutters, dormer cheeks and heads, flat roof upstands, roof lights, and abutments where a lean-to or extension meets a main roof. Each of these locations has its own demands, and the material choice, thickness, and dressing method differ accordingly.
This page's main angle is the choice of material, because it is where homeowners are most often confused or misled. There are four realistic options for lead flashing work in the UK: traditional milled lead, code-specified cast lead, code-specified milled lead, and modern alternatives such as lead-free flashings made from materials like zinc-aluminium alloy or reinforced butyl. Each has a legitimate place, and none is right for every situation.
Milled lead is rolled to a consistent thickness, graded by code number. Code 3 (1.32 mm) is the lightest grade used in roofing and is appropriate for small soakers and cover flashings on shallow pitches in sheltered positions. Code 4 (1.80 mm) is the standard workhorse for chimney flashings, step and cover flashings, and most domestic applications. Code 5 (2.24 mm) and Code 6 (2.65 mm) are used for valley gutters, parapet gutters, and flat roof details where the lead sheet covers a larger area and needs extra stiffness and longevity.
The key practical rule is to never use under-specified lead where the code calls for something heavier. A Code 3 valley gutter, for example, will fatigue far sooner than a Code 5, because lead expands and contracts considerably with temperature. Each bay of a valley should be no longer than 1.5 metres to allow for that movement without cracking - a rule the Lead Sheet Association publishes, and one that is routinely ignored on rushed jobs.
Pros of milled lead: proven hundred-year lifespan when correctly specified and installed; excellent conformability to complex profiles; can be dressed cleanly around tight junctions; universally accepted by building control and insurers.
Cons of milled lead: heavier than alternatives; higher material cost than lead-free products; slow to work with on complex profiles if the roofer lacks experience; theft risk on unattended sites, which matters on larger jobs left partially complete.
Cast lead is made by pouring molten lead onto a sand bed, which produces a slightly uneven surface texture and a denser grain structure than milled lead. It was the standard before rolling mills became widespread. Some conservation officers and listed building authorities specify cast lead for historic buildings because its appearance and working characteristics more closely match original materials.
Pros of cast lead: denser grain can improve longevity marginally; appropriate for conservation and listed building work where specified; excellent patina once weathered.
Cons of cast lead: harder to source than milled lead; more expensive; not required on the vast majority of domestic jobs; heavier per sheet, which matters on fragile historic roof structures.
For most homes in North Walsham, milled lead to the correct code is the right answer. Cast lead is a specialist choice, not an upgrade that every homeowner needs to pay for.
Several manufacturers now produce flashings made from zinc-aluminium alloy strip or from reinforced butyl rubber. These are sold under various brand names and are stocked by most roofing merchants. They are significantly cheaper than lead per linear metre, lighter, and not subject to theft risk. On straightforward applications - a simple step flashing to a chimney, or a straight abutment flashing - they can perform well.
Pros of lead-free alternatives: lower material cost (sometimes 40-60% less per metre than lead); lighter, which reduces load on ageing structures; no theft risk; easier for a less experienced roofer to fit quickly.
Cons of lead-free alternatives: shorter expected lifespan, typically 20-40 years depending on product and exposure, against 60-100 years for properly installed lead; less conformable on complex profiles - they can leave small gaps on irregular masonry; some products are less tolerant of UV exposure over time; not always accepted on listed or conservation buildings; the quality range is wide, and cheaper products perform poorly.
A butyl or lead-free flashing fitted to a sound, uncomplicated detail on a modern house is not a bad choice. It is honest to say so. But on a chimney with complex geometry, on a listed property, or on any junction where longevity matters most, milled lead to the correct code remains the better investment.
Architectural zinc is worth mentioning separately because it is genuinely durable - 60 to 80 years when correctly installed - and is specified on some higher-end new builds and refurbishments. It is harder to work than lead, requires welded or folded joints rather than dressed laps, and needs a roofer experienced with the material. It costs roughly as much as lead or more. For standard domestic flashing repairs in North Walsham, zinc is rarely the practical first choice, but it is a legitimate option if a homeowner wants to match existing zinc on a property.
Chimney flashings are the most common lead work repair on domestic roofs. A properly dressed chimney has four distinct components: the apron (or front) flashing at the downhill face, side step flashings that follow the course of the tiles, a back gutter (the trough behind the chimney stack), and soakers tucked under each tile course at the sides.
Soakers are cut individually and interlace with the tiles, so that water is directed outward even if the cover flashing above is slightly displaced. They are often omitted on rushed jobs, where a continuous piece of lead is turned under the tiles instead. That shortcut lasts only until the mortar pointing holding the cover flashing cracks - at which point there is no secondary defence.
The cover flashings are wedged and pointed into a raked mortar joint, not simply stuck on with mastic. The mortar used to repoint the chase should be a lime-sand mix on older masonry, not a hard cement mix that will crack the brickwork as the chimney moves. Lead-to-masonry joints are a common failure point not because the lead fails, but because the pointing around it shrinks or blows out in frost.
A valley is the internal angle where two roof slopes meet. It carries a heavy volume of water from a large catchment area, and it must be sized and installed to handle that load. Lead valleys should be laid in Code 5 or Code 6 sheet in bays no longer than 1.5 metres, with each bay lapped over the one below by at least 150 mm. The edges must be dressed up under the tiles or slates on each side to prevent wind-driven rain from blowing beneath the covering.
A common failure in older valleys is that the lead has been laid in one long piece. Over time, thermal movement causes the lead to ripple, crack, or pull away at the edges. When we inspect a leaking valley, we often find that the original lead sheet has split along a fatigue line mid-bay - a sign that the bay lengths were too long when it was installed, or that an underspecified code was used.
Dormers introduce multiple vulnerable junctions: where the side cheeks meet the main roof, where the head of the dormer window meets the cheek cladding, and where any flat or pitched dormer roof meets the wall above. Each junction needs a properly formed flashing, and on a timber-framed dormer the whole assembly moves differently from the masonry around it, so allowance for differential movement must be built in.
Felt and batten behind the cheek cladding is not a substitute for a properly formed lead upstand at the base of each cheek. Water that gets behind cladding without a lead upstand to redirect it outward will work its way into the wall plate and cause rot that is expensive to repair.
Where a flat roof meets a parapet wall or a vertical face, a lead upstand sealed into the masonry is the standard weatherproofing detail. The upstand must be tall enough - at least 150 mm above the finished roof surface - to prevent standing water from finding a path behind it. The lead should be secured with lead clips rather than relying on the mortar alone, as mortar shrinks over time.
EPDM rubber flat roofs can be terminated with lead-capped upstands or with proprietary EPDM termination trims. Either approach works if it is done correctly; the failure usually occurs where the two materials are expected to bond to each other without a proper mechanical fixing at the top edge.
Lead work is priced by the job rather than a flat per-metre rate, because the access, complexity, and material code all affect the cost significantly. That said, homeowners should have a realistic sense of the ranges involved when comparing quotes.
These are typical UK figures for 2020s pricing and will vary with scaffolding or access platform costs, which on a tall or awkward chimney can add £300-£600 or more to a job. Any quote that does not address access separately is worth questioning.
Lead itself is traded as a commodity and its price fluctuates. A significant rise in lead prices - which has happened more than once in recent years - will push these figures upward. A roofer who quotes a fixed price without a material price caveat on a large job is either absorbing that risk themselves or has built a large margin into the figure.
Before agreeing to lead work, there are questions worth putting to any contractor, not just us.
A roofer who can answer these questions without hesitation understands the work. One who deflects or dismisses them probably does not.
If longevity is the priority - particularly on a chimney or valley you do not want to revisit for decades - milled lead to the correct code is the sound choice. If budget is the primary concern and the detail is uncomplicated and on a modern building, a quality lead-free alternative is a legitimate option. Cutting lead costs by using an underspecified code or skipping soakers saves money once and costs more later. That is the honest summary.
Aylsham Roofers carries out lead work across North Walsham, Aylsham, and the surrounding villages. If you have a suspected flashing leak or can see cracked or lifting lead from the ground, call us to arrange a roof survey so we can assess what is needed before water causes further damage to the roof timbers or ceiling below.
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Call any time. Calls are answered day and night and passed straight to our roofers.
