Diss Roofers carries out lead flashings, valleys, flat roof lead detailing and chimney lead work for homeowners in Attleborough and the surrounding area.
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Lead work is one of the most skilled trades within roofing, and one of the most misunderstood. Homeowners often assume a flashing replacement is a quick patch job. In practice, a properly executed lead job involves several distinct stages, each of which matters to how long the work holds. This page walks through the full process so you know exactly what a roofer should be doing on your roof - and what questions to ask if something does not look right.
Lead is used at every point on a roof where two surfaces meet and where that junction must remain watertight despite movement in the structure. The main locations are: chimney flashings (front apron, step flashings, back gutter and soakers), abutment flashings where a lean-to or extension roof meets a wall, valley linings between two roof slopes, flat roof upstands and drips, and around dormer windows and skylights.
Each of these details requires slightly different lead-working techniques. A chimney back gutter, for example, involves bossing the lead into a corner to form a watertight internal angle without cutting or welding. A valley is a simpler shape but requires correct lap dimensions and the right code of lead to handle the water volume passing through it.
Before any lead is cut, a roofer should carry out a thorough inspection of the existing detail. For a chimney job, that means checking the lead on all four sides, testing whether it is fixed or has pulled free from the chase, looking for cracks or creep in the body of the lead, and checking the condition of the brickwork and pointing on the stack itself. It also means lifting a few tiles adjacent to the flashing to check whether soakers are present and in good condition.
This initial assessment determines what the job actually involves. A flashing that has simply dropped out of a failed mortar chase may only need re-raking and re-pointing. Lead that has cracked, been over-patched or reached the end of its service life needs full replacement. Getting this call right at the start saves money - replacing lead that could have been re-fixed wastes money, but patching lead that genuinely needs replacing just delays the inevitable.
If replacement is needed, the existing lead comes off first. For chimney flashings, this means removing the step flashings and front apron, extracting the lead wedges from the chase, and then removing the soakers from beneath the tiles. Adjacent tiles are carefully lifted and set aside - any that are cracked or damaged at this stage should be noted so they can be replaced rather than relaid.
The chase in the brickwork is then raked back to remove old mortar. A common fault in old work is a chase that was cut too shallowly - less than 25mm deep - which means the lead never had a proper mechanical fixing and will work loose again in a few years regardless of how good the pointing is. A raker or plugging chisel is used to cut the chase to the correct depth before the new lead goes in.
Lead is supplied in rolls and cut to length on site. The code (thickness) is chosen to suit the application - Code 4 for most flashings, Code 5 for back gutters and valleys, Code 6 for wider flat roof sections. Bay lengths are kept to a maximum of around 1.5 metres for flashings, and shorter for back gutters on steep pitches. This is not a detail to skip - lead in longer bays cannot accommodate thermal movement and will crack at the weakest point within a few seasons.
The lead is then dressed into shape. On straight abutments, this means bending the lead along its length to match the pitch of the roof and dressing it flat against the wall face. On a chimney with angles and corners, the lead is bossed - worked with a bossing mallet in a series of small blows - to form the internal angles without thinning the metal or cutting it. Where bossing is not practical, a welded joint may be used, but this requires proper lead-burning equipment and skill, not a heat gun and improvised technique.
Soakers are cut from a separate piece of Code 3 or Code 4 lead, each sized to cover the depth of the tile plus a 75mm upturn against the wall. They are slipped under each course of tile before the step flashings are dressed over the top.
Each bay of lead is fixed using lead clips or tacks, not nails through the face of the flashing. Nails through the face create a puncture point directly in the water-shedding surface - a quick fix that creates a new leak. Lead clips grip the bottom edge of the flashing and are dressed against the tile surface, holding the lead in position without penetrating it.
The top of each flashing bay is tucked into the raked chase. Lead wedges (sometimes called lead plugs) are driven in at intervals of around 450mm to lock the flashing in position. The chase is then pointed up with a mortar mix - typically a 1:3 ratio of cement and sharp sand, or a proprietary pointing mortar for older brickwork. The pointing is finished flush and tooled to shed water rather than hold it.
Any tiles lifted during the job are relaid in the correct bond, checking that nibs or clips are properly located. Cracked or damaged tiles found during the strip-out are replaced. Valleys need particular care when relaying the cut tiles at the edges - the clearance between tile and valley lead must be sufficient to allow water flow without the tiles bridging the valley.
Once the lead is in and the tiles are back, the area around the base of the chimney or along the flashing run is swept clean. Offcuts of lead, old mortar and broken tile fragments should come off the roof and not be left in gutters or behind chimney pots where they can block drainage later.
A roofer who can answer all of these without hesitation is working to the correct standard. One who cannot explain the bay length reasoning should be pressed further.
We cover Attleborough and the surrounding area, including Wymondham, Long Stratton, Banham, Norton, New Buckenham, Hopton and over to Diss, Scole, Roydon and Pulham St Mary. If you need lead work assessed or replaced, call Diss Roofers to arrange a roof survey and we will talk you through what we find before any work begins.
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Call any time. Calls are answered day and night and passed straight to our roofers.
