Lead Work in Histon - Repair or Replace?

Expert Lead Work
in Histon

Why the Repair-or-Replace Question Matters

Lead is one of the most durable roofing materials available. Correctly installed lead flashings on a chimney or dormer can perform for 50 years or more without attention. When they fail early, it is almost always because of a specific fault in the original installation rather than the lead itself simply wearing out. Understanding that fault determines whether a repair is the right answer or whether you are putting good money after bad.

A one-off repair on otherwise sound lead makes complete sense. Repeatedly patching lead that was poorly installed from the start does not. The sections below explain what to look for and which way the decision usually goes.

What Lead Work Covers - the Basics

Lead flashings seal every junction where your roof covering meets a vertical surface. Chimneys breaking through a pitched roof need step flashings running up each side, soakers between every slate or tile course, and either a back gutter or a saddle at the top of the stack. Dormers need cheek flashings and an apron at the front. Flat roofs that meet a wall need an upstand dressed up the face of the brickwork and turned into a mortar joint at the top.

In every case the lead must be the correct thickness (expressed as a Code number) for the width of the application. It must be fixed with lead clips rather than nailed through, and it must be laid in lengths short enough to allow thermal movement without splitting. When any of those conditions is not met, the lead fails sooner than it should.

When a Repair Makes Sense

There are situations where repairing existing lead is straightforwardly the right answer.

• The mortar joint has failed but the lead is sound. Step flashings are tucked into raked brick joints and pointed up. Frost and age cause that pointing to crack or fall out. The lead itself may still be perfectly good. Re-pointing the joint and re-dressing the lead back into place is a proper repair that should last many more years.
• A single section has lifted or been displaced by wind. If the lead has been blown up at the edge of an apron or a cover flashing, the metal underneath is often fine. Dressing it back and re-fixing it with the correct clips is a straightforward job.
• A small split at a stress point. Lead that has been running in too long a section can split at the point where it is fixed, because the expansion and contraction has nowhere to go. If the split is isolated and the surrounding lead is in good condition, a lead-burned patch or a correctly lapped extension can be an appropriate fix.
• The flashing is otherwise recent and well installed. If flashings are only a few years old and the problem is clearly localised - a corner that was not fully dressed down, for example - repairing just that section is sensible.

When Replacement Is the Right Call

Replacement is the better option in a number of situations that a competent roofer should explain to you honestly rather than just quoting for a patch.

• The lead is the wrong Code for the job. Undersized lead - particularly Code 3 on a wide chimney back gutter or a flat roof upstand - will keep failing regardless of how many times it is patched. The only fix is to remove it and install the correct Code.
• Multiple splits along the same length of lead. When lead has been laid in a run that is too long, thermal stress causes splits at several points. Patching each one individually is a losing battle.
• The lead was secured by nailing through the face. Nails through the face of lead prevent it from moving and cause it to split around the nail hole over time. Once that pattern appears, the whole piece needs replacing.
• Sealant or bitumen mastic has been used to patch the lead previously. This is a sign the lead has been failing for a while and has been temporarily covered up. It is rarely worth trying to work around it.
• The lead is genuinely old and fatigued. Lead that has been in place for many decades can become brittle and crystalline. At that stage it will not dress cleanly and will split on contact with a tool. Replacement is the only sensible option.

The Problem with Sealant Patches

Mastic sealant and bitumen-based products are sometimes applied over failing lead to stop a leak quickly. There are circumstances where a temporary seal is justified - for example, to protect the interior while you arrange proper work. But a sealant patch is not a permanent repair and should not be presented as one. Sealant shrinks, cracks and loses adhesion as the lead beneath it continues to move with temperature changes. Within a season or two, the crack reopens. The original lead still needs proper attention, but now a roofer has to clean off all the old sealant before they can assess or dress the metal.

If you have had mastic applied to a flashing previously and it is leaking again, budget for replacement rather than another patch.

Typical Costs for Repair vs Replacement

Pointing up a sound step flashing on a standard chimney stack might cost £150 to £300 depending on access and the extent of the work. Re-fixing a lifted apron or cover flashing is often in a similar range. Full chimney re-flashing with new lead - new soakers, step flashings, back gutter and cover flashing - typically runs from £400 to £900 on a standard stack, more if the chimney is large or access is difficult. Flat roof upstand and abutment replacement is priced by the linear metre; expect roughly £60 to £120 per metre for correctly installed Code 4 or Code 5 lead depending on the complexity of the junction.

The cost difference between a repair and a replacement is often smaller than homeowners expect. A repair that fails and has to be redone costs more in total than doing the replacement once.

What to Ask Before You Agree to Any Work

Whichever way the decision goes, ask the roofer to explain why. They should be able to tell you the condition of the existing lead, what Code it is, how it was originally fixed, and what will be different about the new installation or the repair. A roofer who cannot explain the cause of the failure is unlikely to fix it correctly.

It is also worth asking whether the surrounding tiles or slates will be disturbed and, if so, whether any that are damaged will be replaced at the same time. Lifting and relaying slates to fit new soakers is part of the job on a pitched roof and should be included in the scope of work.

Cambridge Roofers Covering Histon

We carry out lead work repairs and full replacements in Histon and across Cambridge, including nearby places such as Milton, Girton, Chesterton, Waterbeach and Cambridge itself. We will tell you honestly which option makes sense for your roof and why. Call us to arrange a survey so we can see the lead in place, assess its condition, and give you a clear recommendation before you spend anything.