From the first inspection to clearing up at the end of the job, Haverhill Roofers carries out lead flashing repairs and replacements for homes in Sturmer - and here is exactly what that process looks like.
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Lead work failures are not always where they appear to be. Water that shows up as a damp patch on a ceiling or a stain on a chimney breast can travel along a rafter or a wall plate for some distance before it becomes visible inside. The starting point on any lead work job is getting up to the junction itself and confirming the source before any lead is touched.
On a chimney stack, that means checking the flashing on all four sides - the apron at the front, the stepped flashings on each side, and the back gutter behind the stack. Any one of these can be the leak point, and sometimes more than one is failing at the same time. On a dormer, it means inspecting the junction at the cheeks, the sill and the head. On a valley, it means looking at the full length of the lead from ridge to eaves.
If there is any doubt about where the water is entering, it is better to spend a few more minutes investigating at the start than to replace one section of lead only to find the leak persists because the real source was elsewhere.
Once the leak source is confirmed, the old lead comes out. On most chimneys and abutments, lead is held in place by being wedged into a horizontal groove cut into the mortar joint of the brickwork - this groove is called the chase or raglet. The lead is folded into the chase and then wedged tight with small lead wedges, and the whole thing is pointed over with mortar to seal it.
Stripping the existing lead means removing the mortar pointing, pulling the lead wedges and lifting the flashing away from the masonry. If any of the pointing has hardened significantly into the chase, it may need to be carefully raked out. The chase itself is then brushed clean of old mortar, dust and debris. Any previous sealant or mastic repairs are removed at this stage - and there are often one or two layers of old tape or mastic on a flashing that has been touched by a previous contractor. These have to come off completely before new lead can be fitted properly.
On a valley, the slates or tiles bordering the valley are carefully lifted and set aside so the old lead valley liner can be removed. The timber valley board beneath is inspected for rot or damage at this point. If the board has deteriorated, it is replaced before new lead goes in - fitting new lead over a rotten board is a job half done.
Lead sheet comes in rolls and is cut to size on site. The code of lead used depends on the application: code 3 for soakers, code 4 for most step and cover flashings, code 5 for valley gutters and back gutters. Each piece is cut to the correct width and length - no section should run longer than around 1.5 metres without an expansion joint, because lead expands and contracts with temperature change and longer sections will eventually buckle or pull away from their fixings.
Dressing the lead means working it by hand and with a bossing mallet or dresser to fit the profile of the masonry or roof surface. On a chimney, the stepped flashing follows the mortar courses up the side of the stack, with each step overlapping the one below by at least 65 millimetres. The bottom edge is dressed down over the tiles or slates, and the top edge is folded into the chase. The lead needs to sit flat and tight against the brickwork with no gaps or proud edges that could catch wind or let water behind.
Back gutters behind a chimney stack require a wider section of lead, formed to create a small channel that directs water out and away from the stack. The lead is dressed up the back of the chimney, across the gutter, and then turned under the first course of tiles above. On a low-pitch roof, the back gutter needs to be wide enough to carry any volume of water that accumulates without overflowing. Getting this geometry right is one of the more skilled parts of chimney lead work.
Once each section of lead is shaped and in position, it is secured into the chase with lead wedges driven in at intervals. On longer runs, lead tacks or clips may be used to hold the lower edge of the flashing down against the tiles. The wedges hold everything firm while the repointing is carried out, and they prevent the lead from being lifted by wind.
On valley gutters, the lead is fixed to the valley board with copper clout nails - copper rather than galvanised steel because steel nails will corrode in contact with lead over time. The overlap between adjacent lead sections in a valley is typically 150 millimetres, set to ensure that water cannot track back up between sheets.
With the lead wedged in place, the chase is repointed using an appropriate mortar mix. The mortar should be slightly softer than the surrounding brickwork - a mix that is too hard will crack rather than flex slightly as the building moves. Once pointed, the mortar is finished flush with the face of the brickwork and left to cure. Rushing this step or using a mortar that does not bond properly is another source of premature failure.
On older brickwork, it is worth checking the surrounding mortar joints at the same time. If the pointing around the chase is open or crumbling, water can still get behind the flashing even if the lead itself is perfectly fitted. Re-pointing the immediate area around a new flashing is good practice on any masonry that is showing its age.
Where slates or tiles have been lifted to gain access, they are relaid in the correct order with fresh mortar or clips as appropriate. On a valley, the tiles bordering the lead are bedded back with care - any that are cracked or broken during removal are replaced rather than put back. The whole junction is then checked from above and, where possible, from inside the loft to confirm the repair is sound before coming down.
Old lead, stripped mortar, tile debris and any waste from the job are cleared from the roof and from around the base of the property. Lead offcuts are recyclable scrap and are taken away. Gutters and downpipes adjacent to the work are checked to make sure no debris has been pushed in during the job. Leaving a site tidy is part of the work, not an optional extra.
The time needed for a straightforward chimney flashing replacement on a standard house depends on the condition of the existing lead and the roof around it. A full re-lead of a valley gutter takes longer still if the valley board also needs replacing. More complex jobs - a full chimney re-lead including back gutter and soakers on both sides, or multiple valleys on a larger roof - will take longer. Getting a clear scope of work from the roofer before the job starts means you know what to expect and can plan accordingly. To arrange a survey of your property in Sturmer or nearby, call Haverhill Roofers and we will take a look at what needs doing.
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