Lead Work in Withersfield

Expert Lead Work
in Withersfield

What lead work actually does on your roof

Lead seals the vulnerable junctions on a roof - the points where two surfaces meet and where water would otherwise pour straight through. Chimney flashings, step flashings up a party wall, valley gutters between two roof pitches, aprons at the front of a chimney stack, and soakers tucked under slates or tiles at a dormer all rely on correctly fitted lead to stay watertight. When any of those joints open up, you get a leak.

Lead has been used in roofing for centuries because it lasts, it moulds easily to complex shapes, and it expands and contracts with temperature changes without cracking. No sealant or self-adhesive tape is a long-term replacement for it on a traditional pitched roof. A good lead installation on a chimney, properly fixed and dressed into the brickwork, can last several decades before it needs attention.

Warning signs that your lead work is failing

Some signs are obvious. Others are easy to miss until water damage inside the house forces your hand. Knowing what to look for - from ground level or from a safe vantage point - can save you from a much bigger repair bill.

• Damp patches or tide marks on a chimney breast. Water tracking down from a failed flashing often shows up on the internal face of a chimney breast, sometimes several courses below the actual leak. The stain can look like rising damp when it is not.
• Damp or discolouration in a loft space. Flashings that have lifted or cracked let water in slowly. It can pool on the loft floor or soak into the timbers before you notice it at ceiling level.
• Daylight visible around a chimney or dormer. If you can see light around the base of a chimney stack when you look up from inside the loft, the flashing has either lifted or was never properly bedded.
• Cracked or missing mortar along the flashing chase. Lead flashings are fixed into a groove (the chase or raglet) cut into the mortar joint and then wedged tight. Over time the mortar pointing that locks them in can crack and fall away, allowing the lead to lift in wind or rain.
• Lead that has slipped, buckled or pulled away. You can sometimes see from ground level that a flashing has dropped or is standing proud of the brickwork. Any gap between lead and masonry is a water entry point.
• Sealant smeared over the lead or brickwork. This is a tell-tale sign of a previous bodged repair. Mastic and silicone are not permanent fixes for failed lead. They harden, crack and let water in - sometimes in a worse position than before.
• Dark staining on external brickwork below a chimney or parapet. Algae and moss thrive where water persistently runs. Persistent staining often traces back to a flashing that is no longer doing its job.
• Blistering paint or plaster on a ceiling or wall near a junction. Water working its way down a rafter or wall plate from a flashing leak can eventually reach plasterwork. By the time paint blisters, water has been getting in for some time.

What causes lead flashings to fail

Age is the most straightforward cause. Lead does not last forever, and flashings on houses built in the mid-twentieth century or earlier are often original. Even where the lead itself is intact, the mortar pointing that holds it in the chase deteriorates faster than the lead does. Repointing the chase and re-wedging the existing lead is sometimes all that is needed on an older installation that has not been touched before.

Thermal movement is another cause that is often underestimated. Lead expands and contracts significantly with temperature. If the original installation did not allow for this - for example, if a single piece of lead runs for more than a metre and a half without a proper expansion joint - it will eventually buckle, crack or pull away from the fixings. Each lead section should be no longer than around 1.5 metres for this reason. Longer runs are a common source of premature failure.

Poor original installation is a cause that is harder to spot until you are up on the roof. Lead that was dressed flat rather than turned up into the brickwork, or lead that was simply bedded in mastic rather than properly chased in, will fail within a few years. A repair that uses lead code that is too light for the application - a thin code 3 on a chimney back gutter where code 5 is needed - will also fail early.

Physical damage from foot traffic during other roof work is another culprit. Lead is soft and tears and punctures relatively easily. A carelessly placed ladder or a tradesperson walking across a valley gutter can split or crack the lead in a way that is not always immediately obvious.

Finally, galvanic corrosion can occur where lead is in contact with certain metals - copper, for example. This is less common in domestic roofing but worth checking on older properties where materials from different eras have been mixed.

What a proper repair or replacement involves

A proper job starts with finding exactly where water is getting in, which is not always where the leak appears inside. Once the source is confirmed, old failed lead is carefully removed and the chase cleared of old mortar and debris. New lead is cut, dressed and shaped to the profile of the masonry or roof surface, then wedged into the chase and the joints repointed with a suitable mortar. On chimneys, a stepped flashing follows the mortar courses up the side of the stack, with each step overlapping the one below by at least 65 millimetres. A separate apron covers the front face.

Valley gutters and back gutters behind a chimney require heavier lead (code 5 or code 6) because they carry larger volumes of water. Soakers under slates or concrete tiles at a dormer cheek are individual pieces of lead, one per slate course, which work with the tile and mortar to shed water without a continuous flashing. Each application has its own correct method and the right code of lead for the volume of water it will carry.

Do not ignore the small signs

A slow flashing leak causes gradual but serious damage. Wet timber rots, and replacing a rotten rafter or wall plate costs far more than sorting the flashing that let the water in. If you have spotted any of the warning signs above at your property in Withersfield or nearby, get a roofer up to take a proper look. Call Haverhill Roofers to arrange a roof survey and get an honest assessment of what needs doing.