If you have never had lead work done before, knowing what a proper job looks like from start to finish helps you judge whether the work being carried out on your Potton home is up to standard.
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A proper lead work job starts before any tools come out. The first step is a visual inspection - from the ground with binoculars where that is sufficient, and from the roof where access is needed to assess the condition of the existing flashings, the pointing, and the masonry or substrate around them.
On a chimney stack, this means looking at the front apron, both sides of the stack, the back gutter, and the cover flashings. On a dormer, it means checking the cheek flashings and the junction where the dormer sits into the main roof slope. On a flat roof abutment, it means looking at how high the existing flashing runs up the wall and whether the upstand behind it is sound.
The inspection should give a clear picture of what needs to come off and what, if anything, can be left in place. Not every piece of lead on a chimney fails at the same time. If the back gutter is still sound and the problem is only with the step flashings on one side, a good roofer will tell you that rather than quoting for a full strip-out unnecessarily.
Lead work is almost always carried out at height, so setting up access safely is not optional. On a standard two-storey house, this typically means an extension ladder secured at the top and footed properly, with roof ladders (cat ladders) hooked over the ridge to allow work across the roof slope without damaging tiles or slates.
On taller properties, or where the chimney is set well back from the eaves, scaffolding may be needed. A scaffold is more time and cost but it also means the roofer can work properly around all four sides of a chimney rather than reaching from a ladder, which produces better results.
If a roofer proposes to do a chimney flashing replacement from a ladder alone on a tall or steep-roofed property, that is worth querying - it can mean cutting corners on the work that is hardest to reach.
The existing flashings are removed first. On a chimney, this means cutting or raking out the pointing in the mortar chase that holds the lead edge, then peeling the lead away from the masonry and roof covering below. The lead itself is set aside - it has scrap value and should be included in the price either as a credit or as material removed at no extra charge.
Once the old lead is off, the condition of what is underneath becomes visible. Common findings at this stage include:
If anything unexpected is found at this stage, a good roofer will show you before proceeding - either in person or with photographs - and discuss how it affects the scope of work.
Before new lead goes on, the surface it is being dressed to needs to be clean and sound. On a chimney, this means raking out the mortar chase to an adequate depth - typically 25mm or more - so the lead edge can be properly tucked in and secured. Loose or crumbling mortar should be removed further back to reach sound masonry.
Any tiles or slates disturbed during strip-out are re-bedded or replaced at this stage. If any supporting timbers were found to be damaged, these need to be addressed before the lead goes on - there is no point dressing new lead over a soft or rotten deck.
On a flat roof abutment, the upstand also needs checking. The lead needs a minimum of 150mm of upstand above the flat roof surface to avoid water backing behind it when the flat roof is wet. If the existing upstand is too low, it needs to be built up.
This is the skilled part of the job. Lead sheet is cut to size on site using snips or a knife, then dressed - shaped by hand with a dresser tool - to follow the profile of the tiles, slates or brickwork it is being applied to. Good lead work involves tight, neat bends that bed fully against the surface they are sealing.
Each piece of lead must be kept to a maximum length of approximately 1.5 metres to allow for thermal expansion. Where a run of flashing needs to be longer, separate pieces are used with proper lapped joints between them. Laps need to be in the correct direction so water sheds away from the joint, not into it.
On a chimney stack, the individual pieces are:
Each piece is cut, fitted and checked before the next one goes on. Rushing this stage, or trying to cover too large an area with a single sheet, is where lead work failures start.
Lead flashings on a pitched roof need mechanical fixing to prevent wind uplift. Lead clips - small strips of lead formed into a clip shape - are fixed to the roof deck and folded over the lower edge of each flashing at regular intervals, typically every 500mm. Without clips, the bottom edge of the lead can be lifted by wind and water driven behind it.
Cover flashings are fixed at the top by the mortar in the chase. The lead edge is tucked in, and the chase is re-pointed with an appropriate mortar mix. The pointing should be raked slightly inward at the top to shed water out, not flat or proud of the surface where it will catch the rain.
Once all the lead is dressed and clipped, the mortar chases are pointed. The mortar used needs to be compatible with the masonry - a mix that is too hard can cause the brickwork to crack over time as the lead expands and contracts. A lime-based or moderately soft sand-and-cement mix is often appropriate on older properties.
After pointing, the whole installation is checked visually: every lap, every clip, every piece of pointing. Any tile or slate that was moved during the job is checked to confirm it is properly seated and not bridging the flashing below it.
At the end of the job, all off-cuts, old lead, broken tile fragments and other material should be removed from the roof and from around the property. Gutters directly below the chimney or dormer should be checked and cleared of any debris that has dropped in during the work.
You should be able to walk away knowing exactly what was done, what materials were used, and whether anything else was spotted on the roof that might need attention in future. A brief verbal summary, or a note of any additional findings, is what you should expect from a professional.
We carry out lead work repairs and replacements in Potton and the surrounding area, covering chimney stacks, dormers and flat roof abutments on tiled and slated roofs. If you have a roof leak you suspect is coming from a failing flashing, or you want a proper survey before the problem gets worse, call us to arrange a visit.
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Call any time. Calls are answered day and night and passed straight to our roofers.
