Chimneys, leadwork & roofline

Why do my gutters overflow only in heavy rain?

Short answer: Blockages, inadequate falls, leaking joints, undersized outlets, poor alignment or roof areas exceeding capacity can all cause overflow.

What this means in practice

Chimneys, valleys, abutments, ridges, verges and eaves are where different materials and movements meet. Repairs must address the supporting masonry or timber as well as the visible lead, mortar, plastic or metal finish.

What to check next

  • Clean and water-test first
  • Check outlet and downpipe restrictions
  • Consider capacity before simply replacing a joint

When should you ask a roofer to inspect it?

Arrange close inspection for loose masonry, repeated staining around a chimney, split lead, detached verge units or gutters that still overflow after cleaning. Scaffold-dependent repairs should be grouped where sensible so access is not paid for twice.

Safety first: do not climb onto a roof without suitable access, training and protection. Keep clear of loose coverings, unstable ceilings and water near electrical fittings.

Technical content reviewJ & L Welch Roofing & Paving Services Ltd · Over 20 years of combined roofing experienceReviewed 28 August 2026 · How our answers are produced

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