Plain-English definitions of common roofing terms. Written by Nottingham roofers for Nottingham homeowners.
The progressive corrosion of galvanised steel nails holding roof tiles to battens. Common on concrete interlocking tile roofs built between the 1950s and 1970s across Nottingham estates including Clifton, Bilborough, Bestwood and Arnold. Once nails fail, tiles slip free and the roof becomes unsafe.
Strips of lead sheet used to create watertight junctions where a roof meets a chimney, wall, dormer or other structure. Lead flashings are chased into mortar joints and dressed tight to the surfaces. Code 4 for valleys, code 5 for chimneys.
Glass Reinforced Plastic — a seamless flat roofing system created by layering fibreglass matting with polyester resin over a solid timber deck. GRP has no seams to fail, lasts 30-40 years, and is the standard recommendation for heated extensions in Nottingham.
Ethylene Propylene Diene Monomer — a synthetic rubber membrane used for flat roofing. Applied in large sheets glued to the deck. Lifespan 25-30 years. A good mid-range option for garages and outbuildings where GRP is not justified by budget.
The V-shaped or angular tiles that cap the apex of a pitched roof where two slopes meet. Traditionally bedded in sand-and-cement mortar, now increasingly dry-fixed with stainless steel clips and flexible adhesive for longer life.
A modern roofing underlayer that allows water vapour to pass through while blocking liquid water. Replaces traditional bituminous felt on re-roofs. Dramatically reduces condensation in the roof space and is required on all new roofing work under current Building Regulations.
A traditional mortar made from hydraulic lime, sand and water. Essential for repointing Victorian and Edwardian chimneys in Nottingham because it allows the structure to breathe and flex. Cement mortar traps moisture and causes spalling on softer period bricks.
The horizontal board fixed to the underside of the roof overhang at the eaves. Soffits can be solid or vented — vented soffits provide the primary ventilation route into the roof space and are required on all new roofing work to prevent condensation.
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