Lead is still the most reliable material for sealing the joints and penetrations on a roof. We carry out leadwork repairs and replacements on chimney flashings, valleys, parapet walls and flat roof upstands across Ely and the surrounding area.
Lead flashing is the primary weatherproofing at every junction where a roof surface meets a wall, chimney, dormer or adjacent slope. It sounds straightforward, but doing it properly requires accurate preparation, the right materials in the right thicknesses, and careful dressing by hand. The steps below describe how a lead work job should be carried out from start to finish, so you know what to expect when you book a roofer.
Before any lead is ordered or cut, the roofer needs a proper inspection of the existing work. This means getting on the roof (or onto a scaffold section where access requires it) and examining the flashing at close range. Photographs taken from the ground rarely show the full picture - lifted sections, cracked lead and open chase joints need to be assessed by touch as well as sight.
On a chimney, a thorough inspection covers the front apron, the two sets of step flashings running up the sides, the back gutter behind the stack, and the cover flashing that caps the top of the step flashings. Each element can fail independently, and it is common to find that only one section has failed while the rest remains sound. A good roofer tells you exactly which parts need replacing and which can be left.
At a valley, the inspection looks at whether lead soakers are present under the tiles, whether the valley liner itself is correctly lapped and wide enough for the roof pitch, and whether any previous repairs have been carried out with sealant rather than properly dressed lead.
Where flashings need replacing, the old lead must be fully stripped back. Leaving old lead in place and overlaying it with new material does not work - the underlying deterioration continues and the new material cannot be dressed flat or fixed correctly over the top.
Stripping a chimney flashing means removing the old lead, raking out the mortar from the chase joints in the brickwork, and clearing away any debris from the roof surface and gutter below. On a valley, it means lifting enough tiles or slates to get access to the soakers and liner beneath - the number of courses that need to come up depends on the design of the roof and how the tiles overlap.
Any tile or slate lifted during stripping should be checked before it goes back. Cracked or damaged ones are worth replacing at this stage while access is already open, rather than needing a separate job later.
The top edge of a chimney or abutment flashing is secured by tucking it into a horizontal joint in the brickwork - this cut is called the chase. For new work, the roofer cuts this joint to the correct depth (typically 25mm) using a plugging chisel or angle grinder, clearing it of all old mortar and debris. The depth and cleanliness of the chase determines how securely the lead will be held and how well the pointing will seal over it.
On older properties the brickwork mortar may be soft lime, which requires a different approach to hard modern cement. Raking out too aggressively can damage the brick faces. An experienced roofer reads the brickwork before they cut.
Code 4 lead (1.8mm thick) is used for most step flashings and chimney aprons on domestic roofs. Code 5 (2.24mm) is the correct choice for back gutters, valley liners and any position where water will stand or flow across the lead surface. Using the wrong code is one of the most common ways lead work is underspecified on a price-cutting job.
Each section of flashing is cut to length on site. The maximum length of any single piece should not exceed 1.5 metres - longer sections buckle and crack as the lead expands and contracts with temperature changes. Where the flashing needs to cover a longer run, properly lapped joints are used between sections.
Dressing means shaping the lead sheet by hand (using a dresser tool and a bossing mallet for corners) so it follows the exact profile of the surface it is sealing. On a chimney apron this means the lead laps down over the tiles or slates below and turns up the face of the stack above. Step flashings are dressed to sit tight against each brick course as the flashing steps up the slope. A well-dressed flashing fits closely with no gaps or lifted edges.
Lead clips or wedges are used to lock the top edge of the flashing into the chase. These prevent thermal movement from working the flashing loose over time. Without them, even well-pointed work can eventually shift as the metal expands and contracts through thousands of seasonal cycles.
Once the lead is dressed and clipped, the open chase above it is pointed with mortar to seal water out and lock the lead in place. The mortar mix needs to be compatible with the existing brickwork - a hard cement mortar used on soft old brick can cause the brick face to spall as moisture is driven outward. On older properties a lime-based pointing mortar is often the right choice.
The pointing is finished flush or slightly recessed, never proud of the brick face in a way that channels water toward the lead. Correct pointing is the final weatherproofing layer above the flashing; if it cracks or erodes, water finds the back of the lead and the leak returns.
Any tiles or slates lifted to access valley soakers or abutment flashings are re-laid in the correct bond, with clips or nails as required by the roof design. Before going back on, each tile is checked - cracked nibs, missing pegs or damaged faces are noted and the homeowner is told what was found. Re-laying a tile over a cracked neighbour is a shortcut that simply moves the next problem a few months forward.
Where soakers have been replaced in a valley, the number of tile courses that need re-laying depends on the lap depth, which varies between slate roofs, plain clay tile roofs and concrete interlocking tiles. A correctly relaid valley should leave no exposed fixings, no lifted tile edges and a clean straight line of tiles on both sides of the junction.
All stripped lead, old mortar debris and removed tiles go off site at the end of the job. Lead offcuts are recyclable and should not be left on site or in gutters. The roof surface and any area below the access point should be left clear of debris. If a ladder or working platform has disturbed any plant or paving, that is put right before we leave.
Ely Roofers carries out lead work for homeowners in Willingham and nearby areas, travelling from our base in Ely. If you have a suspected flashing problem, call us to arrange an inspection so we can give you a clear scope of what the job involves.
No obligation · We usually respond within 2 hours
Storm damage, active leak, damaged ridge - we aim to be on-site within 24 hours.
