Lead Work in Cambridge

Expert Lead Work
in Cambridge

Why Lead Work Fails and What to Look For

Lead is the most durable flashing material available for chimneys, dormers, bay windows, valley gutters and parapet walls. When it is correctly dressed and fixed, it will outlast almost everything else on the roof. When it is not, water finds its way in at the very joints and abutments it is supposed to protect. Understanding why lead fails helps you catch problems before damp takes hold in the structure beneath.

Warning Signs You Can See From the Ground

Many lead problems are visible without getting onto the roof. The following are worth looking for from the ground with a pair of binoculars, particularly after a period of frost or heavy rain.

• Lifting or curled flashing. Lead that has not been properly secured will lift away from the wall or chimney stack over time, leaving a visible gap between the lead and the masonry. Wind gets beneath it and accelerates the problem.
• Cracks or splits in the lead face. These appear as dark lines running across the surface. They are most common where lead has been laid in a single, uninterrupted sheet that is too long, causing it to move with thermal expansion and eventually tear itself.
• White or grey staining on masonry. A white powdery deposit around a chimney stack or parapet is often lead carbonate, produced when water runs across bare lead. It shows water is travelling somewhere it should not.
• Mortar missing from lead soakers or step flashing. Where lead step flashing is pointed into a mortar chase, the mortar can crack and drop out over years of freeze-thaw movement. Once the mortar goes, the flashing is no longer held against the wall.
• Moss or vegetation growing at a roof junction. A damp, sheltered joint that is letting water in will often encourage moss or even small plants to establish themselves, particularly at the base of chimneys or along valley lines.

Warning Signs You Can See Inside

Internal symptoms are often the first thing a homeowner notices, but by the time water is showing inside the house the leak has usually been running for some time.

• Damp patches or tide marks on ceilings or upper walls. A stain directly below a chimney breast or a dormer window is a strong indicator that the lead flashing above it has failed.
• Damp smell in a loft or roof void. If you can access the loft safely, a persistent musty smell and dark staining on the timbers around a chimney penetration points to a lead failure above.
• Peeling wallpaper or paint on a chimney breast. Moisture working through a chimney stack from a failed back gutter or soakers will often present as damp on the breast itself, which is easy to mistake for rising damp or condensation.

What Actually Causes Lead to Fail

Lead does not simply wear out in the way that felt or tiles do. Most failures come down to how it was originally installed, or to the cumulative effect of ordinary physical forces on sub-standard work.

Thermal movement. Lead expands and contracts significantly with temperature changes. The correct way to manage this is to lay lead in shorter sections, known as bays, with code-appropriate overlaps between them. A common problem is flashings laid as a single long sheet: the metal has nowhere to go as it moves, so it cracks, pulls fixings out or separates from adjacent materials.

Fixings failing. Lead step flashing is typically secured by clips or by pointing into a raked mortar joint. Lime mortar in older properties can soften and crumble; hard cement repointing over it can crack because it does not flex with the lead. Either way, the flashing works loose.

Inadequate laps and upstands. A flashing needs a sufficient upstand height against the wall or chimney to prevent wind-driven rain from getting behind it. The minimum is generally 75mm, but a good lead worker will assess the exposure and dress the lead higher where the situation demands it. Insufficient upstands are a frequent cause of leaks that look baffling from outside.

Incompatible materials. Lead can react with certain materials, particularly some timbers and cement compounds, causing premature corrosion if not correctly isolated. A roofer who is not experienced in lead work may not recognise this before it is too late.

Poor-quality lead. Domestic lead work in the UK should conform to BS EN 12588. The relevant property is the lead's thickness, expressed as a code number. Code 3 (1.32mm) is a minimum for some soaker applications; code 4 (1.80mm) is widely used for step and cover flashings; code 5 (2.24mm) and code 6 (2.65mm) are specified for valley gutters, back gutters, parapet gutters and flat roof details. Using under-weight lead to save cost is a false economy: thinner lead moves more, cracks sooner and offers less resistance to mechanical damage.

What a Proper Lead Work Repair or Replacement Involves

A thorough lead work repair or replacement means cutting and shaping the lead to fit the specific profile of your chimney, dormer, valley or abutment, rather than using pre-formed sections that may not sit cleanly against the masonry. On a chimney repair this typically involves removing the old flashing, raking out the mortar joint, fitting new soakers beneath the tiles or slates, dressing the step and cover flashing to the correct profile, and pointing the lead back into the chase with a flexible sealant or lime-based mortar as appropriate.

For a valley or parapet replacement the lead is laid in bays with correctly lapped joints, and any boarding beneath is inspected and replaced where necessary before the lead goes down. A back gutter behind a chimney stack requires particular care: it sits in a position where debris can accumulate and where a failure will almost always result in water tracking into the roof structure unseen.

Should You Repair or Replace?

A single lifted flashing that is otherwise in good condition can sometimes be re-fixed and re-pointed without replacement. However, if the lead itself is cracked, has been patched with silicone or bitumen compound, or is moving in multiple places, a full replacement is more cost-effective. Sealants applied over failing lead are a temporary measure only: they do not flex with the lead's thermal movement, and they fail within a few years.

If you have noticed any of the signs described above, call us to arrange a roof survey for your Cambridge home. We can assess whether a repair is viable or whether a full replacement is needed, and give you an honest recommendation.