If you've spotted a damp patch near your chimney or dormer, failing lead work is the most likely cause - here's how to read the warning signs before the damage spreads.
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Lead is one of the most durable materials used on a roof, but it still fails. When it does, the damage it causes can spread quickly and silently into timbers, ceilings and walls before you ever see a stain indoors. Understanding what to look for - and why those signs appear - puts you in a much stronger position when speaking to a roofer.
Newmarket Roofers carry out all types of lead work for homeowners in Chippenham and the surrounding area, from chimney step flashing repairs to full valley replacements.
Most lead failures give visible clues before the leak becomes obvious indoors. The trouble is that those clues are easy to dismiss or misread.
Poor original installation is the single biggest cause of lead failure. Lead must be dressed in short bays with proper allowance for thermal movement. A common problem is lead that was laid in one continuous strip rather than in correctly sized sections with upstands, drips and lap joints. As the metal heats up and cools down with the seasons, it moves - and a strip that is too long will eventually crack or pull away from the chase.
Incorrect fixing is another frequent cause. Lead should never be rigidly fixed at both ends of a section. It needs to be able to slide a little as it expands. Using too many fixings, or using the wrong type, prevents that movement and causes the lead to fatigue and split.
Mortar-only joints are also a recurring problem on older properties. Lead that was simply bedded in mortar without any mechanical fixing or proper chase cut into the masonry will loosen as the mortar erodes. Once the edge lifts, water runs straight in behind it.
Theft is worth mentioning too, particularly on properties with easy access to flat roofs or low-level valley gutters. Lead is a valuable metal and sections do get removed. If you notice a sudden, unexplained leak after a period of settled weather, it is worth checking whether lead is missing rather than just cracked.
Chimneys are exposed on all sides. They move slightly as the house settles and as temperature changes cause the stack to expand and contract independently of the roof structure around it. That movement, over time, opens up the joint between the masonry and the flashing.
A properly detailed chimney uses step flashing (small individual pieces of lead woven between courses of brick as the slates or tiles are laid) and cover flashing (a separate layer that overlaps the step flashing and is wedged and pointed into a cut chase). When both layers are correctly installed, the chimney can move without the joint opening. When only a single layer of lead is used, or when the chase is just pointed with mortar rather than properly cut, movement breaks the seal.
Signs specific to chimney lead failure include damp in the loft directly behind the chimney breast, staining on the chimney breast wallpaper inside the room, and visible cracking where the lead meets the brickwork.
Dormers are another high-risk area. The junction between a dormer cheek and the main roof slope is a notoriously difficult detail to get right. Step flashing is used here too, and it must sit under each tile or slate course. If the original lead was simply tucked under the bottom edge of the cheek cladding without proper integration with the roof covering, it will fail over time.
Bay window roofs - often shallow-pitched or flat - rely on lead at the abutment with the wall above. These small roofs shed a disproportionate amount of water given their size, and any failure in the upstand or the lead drip at the front edge sends water into the bay window frame or the ceiling below.
Parapet walls are another common problem area. The lead flashing that sits on top of a parapet, or that dresses the junction between the parapet and the roof, is under constant exposure. It needs to be in multiple bays with proper lap joints and, where the parapet is capped, the capping and the flashing need to work together.
Not every lead problem needs a full replacement. A small section of lifting flashing can often be re-fixed, re-pointed and dressed back into position if the lead itself is still in sound condition. If the lead is cracked, corroded, very thin from age, or has been patched multiple times already, replacement is the more sensible option.
As a rough guide, lead that is lifting but intact may be repairable. Lead that is split, brittle or missing entirely needs replacing. Any repair to lead that is at the end of its serviceable life will be a short-term fix at best.
If you can see the problem from the ground, call us for a closer look before it costs you more than it needs to. Getting a roofer up to inspect the lead properly, before a small failure becomes a significant leak, is almost always the most cost-effective step.
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