Plain-English definitions of the roofing terms you'll encounter when getting quotes or reading survey reports in Chippenham and Wiltshire.
The corrosion of the original mild steel nails used to fix concrete interlocking roof tiles in properties built between the 1950s and 1970s. After 50–65 years the nails corrode through, leaving tiles resting on the batten but no longer fixed. Widespread across Chippenham's Hardenhuish, Stanley and Cocklebury estates. The only reliable resolution is a full or phased re-roof.
The mortar fillet that secures chimney pots to the top of a chimney stack and sheds water away from the pot base. Flaunching cracks and deteriorates over time through thermal cycling and frost, requiring replacement to prevent water ingress and pot instability.
A weight of milled lead sheet defined by BS EN 12588, 1.80mm thick. The standard specification for general roof valleys, step flashings and apron flashings on domestic properties. Correctly installed code 4 lead lasts 50–80 years.
A heavier weight of milled lead sheet, 2.24mm thick under BS EN 12588. Specified for flat lead roofs, parapet gutters, wide valleys and exposed high-moisture positions such as riverside properties in Hartham and Monkton Park.
Glass Reinforced Polyester, also called fibreglass roofing. A liquid-applied flat roofing system that cures to a seamless, rigid waterproof membrane with no joints. Carries a 25-year material guarantee and is the standard replacement for failed felt flat roofs on Chippenham extensions.
Ethylene Propylene Diene Monomer, a synthetic rubber membrane used for flat roofing. Supplied as a single sheet with taped seams, flexible and durable, with a typical 20-year guarantee. Suited to larger or complex flat roofs.
Natural Hydraulic Lime mortar, a breathable lime-based mortar that is softer than Victorian brick and stone. Mandatory for repointing historic masonry — using hard OPC cement on soft Victorian brick causes the brick face to spall and fail irreversibly.
A slope-by-slope assessment where representative tiles are tested on each roof slope to determine whether the fixing nails have failed. Produces a written verdict identifying which slopes need re-roofing and which are sound, enabling a phased approach where appropriate.
The replacement of failed mortar bedding along the ridge line of a roof, using flexible ridge mortar rather than rigid cement. Loose ridge tiles are re-bedded at the same time. Required every 20–40 years on most pitched roofs.
A protective oil applied to newly installed lead on completion to slow natural weathering and prevent white lead carbonate run-off staining the masonry or render below. Applied as standard on all new lead work.
The internal angle where two roof slopes meet, lined with lead or a preformed valley to channel water. Valley failures — particularly on Victorian clay tile properties in Chippenham — are a common cause of water ingress.
The fascia is the board running along the lower edge of the roof to which guttering is fixed; the soffit is the underside board closing the eaves. On 1960s–70s Chippenham properties the original timber is now rotten and typically replaced in UPVC.
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