Plain-English definitions of the roofing terms Warwickshire homeowners come across most often. Any questions about your own roof? Call Stratford Roofing Experts on 01789 509542.
Nail sickness is the corrosion and failure of the nails that hold roof tiles in place, causing tiles to slip out of position. It is widespread on Warwickshire's post-war estates — including Stratford's Bridgetown and Clopton areas — where 1960s and 1970s concrete tiles are now decades old. Once failure is widespread, re-roofing with new fixings is more economical than repeated repairs.
Lead flashing is the weatherproofing detail, formed from sheet lead, that seals the junction where a roof meets a vertical surface such as a chimney, wall or dormer. Correctly installed code 4 or 5 lead lasts 80 years or more. On Stratford's Victorian properties, flashing failure — usually at the pointing rather than the lead itself — is the single most common cause of water ingress.
Hydraulic lime mortar is a traditional mortar used on pre-1919 buildings in place of modern Portland cement. It is softer and more breathable than cement, allowing moisture to escape through the mortar joint rather than through the brick or stone. On Stratford's conservation-area and listed properties, lime mortar is required — cement traps moisture and damages historic masonry over time.
The ridge is the horizontal apex line where two roof slopes meet; the verge is the edge of the roof at a gable end. Both are traditionally bedded in mortar and are the most wind-exposed parts of a roof. In Warwickshire's exposed Feldon locations, mortar bedding fails through freeze-thaw within 20 to 35 years. BS 5534 now requires mechanical fixing of ridge tiles on re-roofed work.
GRP (glass-reinforced plastic) is a liquid-applied fibreglass flat-roof system that cures into a single seamless waterproof membrane. It has a design life of 25 to 30 years and is fully impermeable, which makes it well suited to the higher humidity of the Avon Valley around Stratford. GRP requires a surface temperature above about 5°C to cure, limiting winter installation.
EPDM is a synthetic rubber flat-roof membrane supplied in large sheets and bonded to the deck with contact adhesive. It has a design life of 20 to 25 years, installs in colder conditions than GRP, and is highly flexible. Its main weakness is the adhesive seams between sheets, which makes installation quality the key factor in how long an EPDM roof lasts.
Breathable underlay is the membrane fitted beneath roof tiles that keeps rain out while allowing water vapour from the loft to escape, preventing condensation. It replaced older bitumen felt, which trapped moisture and caused the timber decay common in older Stratford roofs. Modern Warwickshire re-roofs use breathable underlay as standard, often combined with eaves and ridge ventilation.
Flaunching is the sloping bed of mortar at the top of a chimney stack that holds the chimney pots in place and sheds rainwater away from the flue opening. When flaunching cracks — common on Stratford's Victorian chimneys after decades of weathering — water enters the top of the stack and pots can loosen or tilt. Re-flaunching is a routine part of chimney repair.
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