Plain-English definitions of the roofing terms Canterbury homeowners come across — with local context for East Kent properties.
This glossary explains the roofing terms Canterbury homeowners most often encounter — from nail sickness and lead flashing to GRP and repointing. Each definition includes local context for Canterbury and East Kent. For advice on any of these, call Canterbury Roofing Experts on 0122 763 4920.
The corrosion and failure of the galvanised nails that fix roof tiles to the battens. Common on Canterbury's post-war and 1960s–70s concrete tile estates, it causes tiles to slip even though the tiles themselves remain sound. Once around 25–30% of fixings have failed, a full re-roof is usually more economical than repeated re-fixing.
The strips of lead sheet that seal the junctions between a roof and a chimney, wall or valley. Lead flashing is the most common leak point on Canterbury's Victorian terraces. Code 4 lead is standard inland; Code 5 is used in coastal areas like Whitstable and Herne Bay where salt air accelerates corrosion. Correctly fitted, it lasts 25–40 years.
A flat rectangular clay roofing tile, roughly 265mm by 165mm, laid in a double-lap pattern. It is the traditional roof covering across Canterbury and East Kent and is required by conservation area rules on most period properties. It costs more than concrete tile but lasts 60–100 years and matches the historic roofscape.
The renewal of the mortar joints on a chimney stack, ridge or verge. On Canterbury properties built before 1919, lime mortar must be used rather than cement, which is too hard for the soft period brick and causes spalling. Repointing a chimney stack typically costs £150–£500 depending on size and access.
Glass-reinforced plastic, a seamless liquid roofing system applied over a flat roof and cured into a solid waterproof layer. GRP is the standard flat roof replacement for Canterbury extensions and garages, carrying a 25-year guarantee. It significantly outlasts felt and is ideal for complex shapes with upstands and trims.
A synthetic rubber membrane laid as a single sheet over a flat roof. EPDM is durable, flexible in cold weather, and carries a 25–35 year design life. It suits simple rectangular flat roofs and is a lower-cost alternative to GRP for Canterbury garages and outbuildings, performing far better than short-life felt.
The tiles that cap the apex of a pitched roof where the two slopes meet. On older Canterbury properties these are bedded in mortar, which cracks and fails over decades — especially on exposed downland properties around Bridge and Wye. Modern practice uses a dry ridge system, which is mechanically fixed and needs no mortar maintenance.
A roof valley is the internal angle where two roof slopes meet, channelling rainwater to the gutter. Valleys are the most blockage-prone part of a roof, particularly on Canterbury properties under heavy tree canopy near the Stour. Blocked or failed valleys are a leading cause of leaks and require lead or GRP lining to stay watertight.
Need any of these explained for your property?
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