Lead Work in Gressenhall

Expert Lead Work
in Gressenhall

Why Leadwork Fails - and What It Looks Like From Inside

Lead flashings are the thin strips of dressed metal that seal every junction where a roof meets a vertical surface: around chimneys, along the edges of dormers, at the sides of bay windows, and in the valleys where two roof slopes meet. When they fail, water gets in. The frustrating part is that the failure point is rarely obvious from ground level, and the leak can appear well away from where the water is actually entering.

A common pattern is a damp patch on a bedroom ceiling that appears after heavy rain, yet the ceiling is nowhere near the chimney. Water travels along rafters and roof timbers before it drips, so the stain you see can be a metre or more from the source. This is why leadwork faults so often go undiagnosed for a season or two, causing rot to timbers and damp to plasterwork long before anyone realises what is happening.

The Warning Signs to Look For

You do not need to get on the roof to spot most of the early indicators. The following signs all point toward a leadwork problem rather than a tile or slate issue:

• Damp patches or tide marks on ceilings directly below, or slightly downslope from, a chimney or dormer
• Peeling paint or bubbling plaster on an interior wall that backs onto a chimney breast
• A musty smell in a bedroom or loft that gets worse in wet weather
• Visible daylight or staining around the base of a chimney stack when viewed from inside the loft
• White chalky deposits (efflorescence) on the outside of a chimney breast - a sign moisture is working through the masonry
• Flashing that looks lifted, buckled or separated from the brickwork when seen from a bedroom window or with binoculars
• Old mortar pointing along the top of a flashing that has cracked or fallen away entirely

Any one of these is worth acting on. Two or more together make a leadwork survey a clear priority.

What Actually Causes Leadwork to Fail

Lead is one of the longest-lasting roofing materials available - correctly installed code 4 or code 5 flashings can perform well for many decades. When lead fails early, the cause is nearly always one of the following.

Incorrect fixing method. Lead expands and contracts with temperature changes. If it is fixed too rigidly - nailed at too many points or bonded with adhesive along its full length - it cannot move. The metal then splits or pulls away from the brickwork. Traditional lead dressing uses copper clips or tacks spaced to allow movement, and the lead is dressed into a mortar chase rather than simply stuck to the surface.

Wrong thickness (code) of lead. The code number refers to the weight per square foot in pounds, and therefore the thickness. Code 3 lead (1.32mm) is sometimes used by less careful contractors to save money, but it is not suitable for flashings exposed to the weather. The correct specification for most flashings is code 4 (1.80mm) or code 5 (2.24mm) depending on the application. Undersized lead works loose and splits faster.

Mortar joints that have failed. Flashings are tucked into a raked-out mortar joint in the brickwork and then re-pointed. If that pointing crumbles - which it will eventually do on older properties - water gets behind the flashing and the seal is broken. This is not always a sign the lead itself has failed; sometimes re-pointing and re-dressing the existing lead is enough if the lead is in otherwise good condition.

Previous poor repairs. A strip of flashing tape or a bead of sealant is not a repair - it is a temporary measure at best. Mastic and adhesive tape degrade in UV light and become brittle within a few years. They also hold water at the edges of the tape, which speeds up the underlying problem. On older homes, it is common to find two or three layers of failed tape repairs sitting on top of leadwork that was already deteriorating.

Age and fatigue. Even properly installed lead has a lifespan. Lead that was laid forty or fifty years ago may simply have reached the end of its useful life. It becomes thinner as it oxidises, and repeated thermal movement eventually causes hairline cracks that are invisible from the ground but let water through with every downpour.

The Junctions Most Likely to Cause Problems

Not all leadwork is equally at risk. The locations that account for the majority of leak calls are:

• Chimney flashings - There are typically several pieces of lead at a chimney: a back gutter, two side step flashings, and an apron at the front. Each is a separate point of potential failure, and they all need to work together. Chimneys are also exposed to the most thermal movement because they project above the roof line.
• Valley gutters - Where two slopes meet, a lead-lined valley carries a high volume of water. Debris builds up in valleys, and if the lead has lifted at any point, water backs up behind it.
• Dormer cheeks and heads - The junction between a dormer wall and the main roof slope is often awkward to dress neatly, and poorly executed work here lets water run down inside the wall.
• Bay window roofs - Flat or shallow-pitched bay roofs rely on correct upstand flashings where they meet the main wall. These are often under-specified on older properties.

When to Repair and When to Replace

If the lead itself is structurally sound - no splits, no severe thinning, no cracking - and the problem is limited to failed mortar pointing, a re-point and re-dress may be all that is needed. If the lead has split, buckled, or been previously patched with tape, full replacement with new correctly specified lead is the right answer. Patching cracked lead rarely holds for long.

If you are unsure, the honest approach is to have someone get up on the roof and look properly before committing to anything. That survey should tell you exactly what you have and what it will take to fix it.

Leadwork for Gressenhall Homes - What to Ask

When speaking to any roofer about leadwork, ask them to confirm the code of lead they intend to use. For chimney flashings and valleys, code 4 is the minimum, and code 5 is appropriate for wider applications. Ask how they intend to fix the lead - it should be dressed into a mortar chase and clipped, not glued or over-pointed. And ask whether the chimney pointing and brickwork will also be checked, because lead repairs on a chimney with failing mortar joints will not last.

Dereham Roofers serve Gressenhall and the surrounding villages. If you have spotted any of the warning signs above, call us to arrange a roof survey and we will tell you plainly what the problem is and what needs doing.