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Chimney Leaks and Lead Flashing: Causes and Fixes

By Staff4dshire Group · Staff4dshire Roofing Specialists

Some of the most stubborn roof leaks have nothing to do with the slates or tiles themselves. They come from the junctions: where the roof meets a chimney, a wall, a valley or a dormer. Those junctions are usually sealed with lead, and when the lead or the mortar around it fails, water finds its way in. Here is how to spot the problem and what a proper repair looks like.

Chimney Leaks and Lead Flashing: Causes and Fixes

Signs your chimney or flashing is leaking

Damp patches on the chimney breast or ceiling near the stack, especially after heavy rain or driving wind, are a classic sign. You might also see staining in the loft around the chimney, damp timbers, or water marks where a roof meets a wall.

From the outside, look for lead that has lifted, cracked or slipped, missing or crumbling mortar around the stack, and slipped or broken slates or tiles next to the chimney. Binoculars from the garden are safer than climbing a ladder.

How lead protects a chimney

Around a typical chimney there are several pieces of lead working together. Step flashings run up the sides, tucked into the brick joints and dressed over the roof covering. An apron flashing runs across the front, and a back gutter at the rear collects water running down the roof and directs it round the stack. Each piece overlaps the next so water always runs out and away.

If one piece is too short, has lost its fixings, or has been replaced with a sealant or tape, the whole system can fail. Lead also needs room to expand and contract; very long pieces or pieces fixed too tightly can crack over time.

Valleys, bays and dormers

The same principles apply wherever two roof slopes meet or a roof meets a vertical surface. Lead-lined valleys carry a lot of water, so debris, slipped tiles or worn lead can quickly cause leaks. Bay windows and dormers have their own flashings and lead coverings that need the same care.

When we carry out leadwork we look at the whole junction, not just the obvious split, because the visible damage is often the end of a longer story.

Pointing and the stack itself

A chimney can also let water in through the brickwork and joints. Weathered mortar, a cracked flaunching around the pots or damaged brickwork will all let water soak into the stack. On older properties we often use lime mortar, which lets the masonry breathe; on others a traditional compo (sand and cement) mix is appropriate. Matching the method to the building matters.

What a proper repair involves

A lasting repair usually starts with safe access, normally a chimney scaffold, so the work can be done properly rather than from a ladder. We then strip out failed lead, rake out joints, renew flashings and back gutters with correctly sized, properly fixed lead, repoint where needed and make good the slates or tiles around the stack.

Sealants and tapes can buy time in an emergency but are not a substitute for correctly detailed leadwork.

Fine detailing makes the difference

Our team puts a lot of care into fine detailing around chimneys, abutments, valleys, hips and edges, because that is where most leaks start. Whether your property is a period house in Lichfield or a newer home in Cannock, the same attention to detail applies.

Book a roof inspection

Staff4dshire Roofing Specialists carry out leadwork, chimney repairs, pointing and roof repairs across Staffordshire and the West Midlands, with scaffolding organised through our own scaffolding company. Send us a few photos and your postcode and we will arrange a visit.

Quick checklist

  • Note when the damp appears (wind, heavy rain)
  • Look for lifted or cracked lead
  • Check mortar and flaunching around the pots
  • Check slates and tiles next to the stack
  • Avoid sealant-only fixes
  • Plan a chimney scaffold for safe access

Frequently asked questions

Can a chimney leak be fixed without scaffolding?

Small inspections can sometimes be done from other access, but proper repairs to lead and brickwork are best done from a chimney scaffold.

Should I remove an unused chimney?

That is a bigger decision involving structure, ventilation and sometimes planning. If the stack is sound, repairing the lead and pointing is often simpler.

Lime or cement mortar?

Older, solid-walled buildings often need lime mortar so the masonry can breathe. Newer brickwork can usually take a traditional sand and cement mix. We match the method to the building.

About Staff4dshire Group. Staff4dshire Group is based at Unit 7 & 8 Kimberley Business Park, Rugeley, Staffordshire. Our companies cover building and landscaping (Staff4dshire Properties), roofing (Staff4dshire Roofing Specialists), scaffolding (Staff4dshire Scaffolding), groundworks, drainage and utilities (Staff4dshire Groundworks & Utilities), plant hire (Staff4dshire Plant Hire) and renewables (Margav Energy). We work for homeowners, developers, principal contractors and local authorities across Staffordshire, Birmingham and the West Midlands, and we are a registered supplier with Walsall, Tamworth, Sandwell, Dudley, Birmingham and Telford & Wrekin councils.
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