Understanding what a proper lead work job looks like from start to finish helps homeowners in Girton ask the right questions and recognise quality when they see it.
Before any lead is lifted or dressed, a proper inspection needs to happen. A roofer should look at the lead itself, the masonry or timber it is fixed to, and the area immediately around it - both from the roof and, where accessible, from inside the loft. The source of a leak is not always directly above where the damp appears inside, because water can travel along a rafter or batten before dripping onto a ceiling.
On chimneys, the inspection covers all four sides: front apron, back gutter, and both runs of step-and-soaker flashings. On dormers, it means checking the cheek flashings, the head flashing where the dormer meets the main roof slope, and the sill flashing at the base. On a flat roof abutment, it means examining the upstand height, the condition of the lead and whether it has started to lift or pull away from the wall.
A thorough inspection takes time. If a roofer gives you a price for lead work without properly examining all the relevant areas, that is worth questioning.
Once the extent of the work is clear, the existing lead has to come off. Old lead is cut back and removed in sections. On chimneys, this means carefully lifting the flashing out of the raglet - the chase cut into the mortar joint where the top edge is tucked. The raglet is then cleaned out, and any loose or crumbling mortar is raked back further to give a clean bed for the new lead.
The masonry or timber beneath is inspected once the lead is removed. It is at this point that additional problems sometimes become apparent: saturated timber battens, spalled brickwork, or mortar that has softened right through. Any of these need to be addressed before new lead goes on. Putting good lead over damaged structure underneath is a false economy.
For valley work, the old lead valley is lifted back from the tile courses on each side, and the underlying boards or sarking felt are checked for rot or damage. Any sections that are soft or crumbling need to be replaced before the new valley is laid.
This is the skilled part of the job, and it is where proper lead work differs from a rushed fix. Lead sheet is supplied in rolls or flat sheets and is cut to length on site using snips or a knife. Each section is then hand-dressed - worked with lead dressing tools - to fit tightly against the surface it is sealing.
Lead should be hand-dressed on site to BS EN 12588 standard. This standard sets the minimum thicknesses for each code of lead, and specifying the right code for each location is part of doing the job properly. Step flashings on a chimney, for example, are typically Code 4. Valley gutters and back gutters need Code 5 because they carry water and are exposed to more thermal movement.
Each section of flashing is kept to no more than around 1.5 metres in length. Lead expands and contracts with temperature, and longer runs will develop cracks along their length as the metal fatigues. Overlapping short sections correctly avoids this. The overlap between sections should be at least 100mm to prevent water tracking back up between them by capillary action.
Where step flashings meet soakers, the soakers go on first - laid under each tile course - and the cover flashings are dressed over them. The cover flashings are not fixed to the soakers; they work independently, which allows both to move slightly without breaking the seal.
The top edge of each flashing section is tucked into the raglet and fixed with lead wedges driven into the joint to hold it firm. Lead clips are also used at intervals along the length to stop the lead from creeping downward under its own weight over time. Without these fixings, warm weather causes the lead to expand and gradually slip, eventually opening a gap at the top edge where water can enter.
Once all sections are in position and wedged, the raglet is pointed up with fresh mortar. This pointing has two purposes: it seals the top edge of the flashing against water entry and it holds the lead wedges in place. The mortar used needs to be the right mix - too strong a mix becomes brittle and cracks away faster than the original, too weak and it washes out quickly. A sand-and-cement mix gauged to the hardness of the surrounding masonry is correct for most jobs.
Once all the lead is dressed and pointed, a final check is made to confirm that water has a clear route off the roof at every point. On a back gutter behind a chimney, for example, there must be a positive fall toward the sides and down through the soakers - standing water in a back gutter accelerates corrosion and will eventually leak. On a flat roof abutment, the upstand needs to be tall enough to prevent wind-driven rain from getting behind it - a minimum of 150mm is the general requirement.
The area below is tidied as work progresses. Lead offcuts, old mortar and any broken tile pieces are collected and removed. If any tiles were lifted to gain access or to fit soakers, these go back correctly seated and checked for any that may have cracked during the process.
A good lead job leaves the roof looking neat and the flashing sitting tightly at every junction. If you can see gaps between the lead and the surface it is meant to seal, or if the mortar pointing looks rough and porous, these are signs the job has not been done to the right standard.
If you have damp near a chimney, dormer or flat roof junction in Girton, or you want a clear picture of what a lead repair or replacement will involve before you commit, call Newmarket Roofers for a roof survey. We will walk you through what we find and what the work entails before any lead is touched.
No obligation · We usually respond within 2 hours
Storm damage, active leak, damaged ridge - we aim to be on-site within 24 hours.
