If you have a lead flashing, valley, or flat roof section that is leaking or ageing, Mildenhall Roofers carries out hand-dressed lead work in Waterbeach to the correct Code and specification.
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Lead is one of the oldest roofing materials in use and still one of the most reliable when it is installed correctly. It is used in several distinct situations on a roof: as flashing where a roof slope meets a wall, chimney, or dormer; as a valley lining where two slopes meet; as soakers tucked beneath tile courses at abutments; and occasionally as a flat roof covering on smaller sections such as bay roofs or canopy tops. Each situation requires different lead thicknesses, different fixing methods, and different detailing at the edges.
All lead used in quality roofing is graded by Code, which refers to its thickness and weight per square metre. The Code determines how long the lead will last and how well it will resist the expansion and contraction that happens every time the temperature changes. Getting the Code wrong is one of the most common reasons lead work fails prematurely.
Lead failure is rarely sudden. It tends to develop gradually, which is why many homeowners do not notice it until water has been tracking in for some time. A common problem is lead that was dressed too tightly around a chimney or parapet, leaving no room for thermal movement. Over years of heating and cooling, the lead cracks along the fold lines or pulls away from the mortar joint it was tucked into.
Another frequent cause of failure is lead that was fixed with too many nails or clips placed too close together. Lead needs to be able to move slightly as it expands. Pin it down in too many places and it will tear at the fixings rather than move freely. The result looks like small splits or perforations along the fixing line.
Flashings that have been repointed without being re-bedded properly are also a source of leaks. The mortar can look sound on the outside while the lead itself has lifted away from the wall behind it. Water gets in behind the flashing rather than being directed over it.
On valley leadwork, a common problem is lead that was cut too narrow. Building regulations and the Lead Sheet Association both give minimum girth dimensions for valleys, and undersized lead cannot contain the volume of water running down from both slopes in heavy rain. This leads to water overflowing the valley and entering the roof structure below the tiles.
Visible signs that lead work needs attention include staining on internal ceilings near chimneys or gable walls, white chalky deposits (efflorescence) on chimney brickwork just below the flashing line, visible gaps or cracks in the lead itself, mortar that has dropped out of the chase where the flashing is tucked in, and daylight visible between the lead and the surface it is meant to seal against.
This is the section most homeowners find confusing, so it is worth explaining clearly. Lead sheet is sold by Code number, which runs from Code 3 up to Code 8 in standard roofing use. The Code refers to the weight in pounds per square foot of the original imperial system, but the number itself is what matters in practice.
A flashing installed in Code 3 where Code 5 was required will not last. It will stretch, crack, and fail within a few years even if it was dressed correctly. Always ask a roofer which Code they are specifying for each part of the job, and why. A knowledgeable roofer will give you a direct answer.
Lead is not the only material used for flashings and valleys. Alternatives include aluminium, zinc, and various proprietary self-adhesive products. Each has genuine strengths and weaknesses. The table below sets out the honest picture so you can have an informed conversation with any roofer you speak to.
Pre-formed aluminium flashings are sold in rolls and are easier to install than lead, which is partly why some roofers prefer them. They are lighter, cheaper, and do not require hand dressing to the same degree. On straightforward flat-profile abutments they can perform adequately. However, aluminium does not dress as cleanly around complex shapes, it can oxidise and become brittle in exposed positions over time, and pre-formed sections are only available in standard profiles - anything non-standard requires lead or zinc. For chimney work on older properties with uneven brickwork, aluminium rarely achieves a clean seal.
Products such as self-adhesive bituminous tape are sometimes used as a quick fix on flashings. They can seal a leak temporarily and have their place as an emergency measure. They are not a permanent replacement for properly dressed lead. Adhesion degrades in UV exposure, they lift at edges over time, and they cannot be pointed into a masonry chase the way lead can. Any roofer proposing self-adhesive tape as a permanent flashing solution on a chimney or valley should be questioned carefully.
Zinc is a genuine alternative to lead on some applications and is used more commonly in continental Europe. It requires different detailing - longer individual pieces with different expansion allowances - and is not as forgiving of poor technique as lead. It is less familiar to most UK roofers and should only be specified by someone with experience working with it. On like-for-like replacements of existing lead work, lead is almost always the correct choice.
Lead work pricing varies depending on the Code specified, the complexity of the detail, and the access required. As a guide, chimney flashing replacement in Code 5 lead on a standard two-chimney semi-detached property typically costs in the range of £400-£900 depending on chimney size, the number of faces involved, and whether a back gutter is required. Lead valley replacements on a typical hipped or gabled roof range from roughly £600-£1,500 depending on valley length and the tile type on either side. Smaller individual flashing repairs - a single step flashing or a small apron - may be as little as £150-£300 if access is straightforward. These are typical current UK ranges and your specific job should always be quoted individually after inspection.
The cost of lead itself moves with commodity prices, so any quote older than a few months should be confirmed before you proceed. Code 5 lead sheet currently costs considerably more per square metre than Code 3, which is why some less scrupulous contractors underspecify the Code to win on price. Ask specifically what Code is being used and get it in writing.
Good lead work has a clean, even appearance. Each piece of lead is dressed tightly to the surface it is sealing against, with no gaps, lifted edges, or visible nail heads on the face. At chimneys, the top edge of the flashing should be tucked into a raked-out mortar joint (the chase) and pointed back in with an appropriate mortar or leadmate compound - not just stuck against the face of the brickwork with sealant. The lead should sit flat against the tile or slate surface below, not bridging over an air gap.
At valleys, the lead should extend far enough under the tiles on both sides to prevent overflow in heavy rain, and the visible centre of the valley should run in a clean, straight line. The lead is secured with lead clips or tacks at intervals that allow thermal movement - not nailed flat at every edge.
Joints between lead sections (soakers at each tile course, for example) should overlap correctly and not be bridged with sealant. Sealant on lead work is sometimes used as a finishing detail in specific situations, but if a roofer is relying on mastic to make the flashing watertight rather than the lead itself doing the job, that is a warning sign.
Lead work is one area of roofing where the quality difference between contractors is particularly significant. These are the questions worth asking any roofer before they start:
A roofer who is comfortable answering these questions directly - without vague reassurances - is more likely to do the work correctly than one who brushes them off. If you are unsure about any of the answers, a second opinion from a different roofer before committing is always reasonable.
Mildenhall Roofers carries out lead flashing, valley, and flat roof lead work across Waterbeach and the surrounding area. Lead should be dressed by hand to the correct Code for each application. The Code should go on the quote so you know exactly what you are getting.
If you have a suspected lead failure - whether that is a leaking chimney, a wet patch near a valley, or visible cracking in an existing flashing - call us to arrange a roof survey and we will give you a straight assessment of what is wrong and what it will take to fix it properly.
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Call any time. Calls are answered day and night and passed straight to our roofers.
