Plain-English explanations of the roofing terms Northampton homeowners encounter — from nail sickness to lead flashing. Call 0160 428 1189 for a free survey.
This glossary explains common roofing terms for Northampton homeowners in plain English. Whether you've been told your roof has nail sickness, failed lead flashing or perished pointing, these definitions help you understand what your roofer means and what work your property needs.
The corrosion of steel nails that fix roof tiles to battens, causing tiles to slip and fall. It is widespread on Northampton's 1960s–80s concrete tile estates such as Blackthorn and Rectory Farm, where the original fixings have reached the end of their 40–60 year corrosion life. The remedy is re-fixing with stainless steel nails.
A modern roofing underlay fitted beneath tiles that allows water vapour to escape from the roof space while keeping rain out. It replaced traditional bitumen felt, which has a 60–80 year lifespan and has failed on many older Northampton roofs. Breathable membrane improves loft ventilation and reduces condensation.
Dressed sheet lead that waterproofs the junctions between a roof and chimneys, walls or valleys. Correctly installed to the right lead code, it lasts 50–100 years. On Northampton's Victorian and 1930s properties, failed lead flashing is the most common cause of persistent damp. Sealant is not a durable substitute.
Lifting and relaying ridge or hip tiles in fresh mortar when the original bed has failed. Different from re-pointing, which only replaces the surface joint. On period Northampton properties, re-bedding uses lime mortar; on post-war concrete tile roofs, a gauged sand-and-cement mix. Rocking or displaced ridge tiles require re-bedding.
The edge of a roof at the gable end, where tiles meet the outside wall. Verges are traditionally mortar-bedded but can be finished with dry verge systems on modern roofs. Failed verge mortar allows wind and water under the tiles and is a common repair on Northampton's exposed estate properties.
The horizontal underside of the roof overhang, spanning from the fascia board to the external wall. Soffits are ventilated to allow air into the roof space and prevent condensation. On older Northampton homes, timber soffits rot and are replaced with maintenance-free vented uPVC lasting 25–40 years.
Glass Reinforced Plastic, a seamless flat roofing system applied as a liquid that cures to a hard waterproof surface. It lasts 35–50 years — far longer than traditional felt's 10–15 — and handles the East Midlands freeze-thaw cycle well. GRP is the most common flat roof choice on Northampton extensions and garages.
The mortar finish applied to the joints of ridge tiles, hips and chimney brickwork. Over 25–40 years it erodes through weathering, allowing water in. Re-pointing on Northampton's Victorian and 1930s properties requires lime mortar — hard cement causes the brick or tile face to spall through differential movement.
Not sure which of these applies to your roof? Book a free no-obligation survey and we'll tell you plainly.
0160 428 1189Last updated: August 2026