Why is my roof leaking? The most common causes
The usual reasons roofs leak, how to narrow it down, and why the stain inside is rarely directly under the problem.
Slates and tiles
Slipped, cracked or missing slates and tiles are the most visible cause. On older slate roofs, corroded nails let slates slide out one by one.
Flashings and junctions
Where a roof meets a chimney, wall, dormer or roof window, lead flashing keeps water out. When it lifts or cracks, water runs straight in.
Gutters, valleys and parapets
Blocked gutters and valleys overflow behind fascias and into walls. City buildings with hidden parapet gutters are particularly prone to this.
Flat roofs
Ageing felt splits and blisters, and poorly detailed upstands let water in at the edges.
It might not be a leak
Damp that appears in cold, dry weather can be condensation. An inspection separates the two so you don't pay for the wrong fix.