Flashings, ridge, verge & pointing in Macclesfield

Junctions leak. The flat middle of a roof rarely fails — what fails is every place the roof meets something else: a wall, a chimney, another roof plane, or the open edge at the verge. Nearly all routine roofing work is at these junctions, and nearly all of it is mortar or lead.

The single biggest change in this part of the trade came in 2014, when BS 5534 was revised. Mortar bedding on its own is no longer an accepted fixing for ridges, hips or verges — every unit has to be mechanically fixed as well, either with a dry-fix system or with clips and screws under a traditional bed. It is a genuine improvement and not a sales tactic: bedded-only ridges are precisely what comes off in a gale.

Dry ridge and dry verge systems do away with the mortar entirely — a ventilated ridge roll and mechanically fixed units, and a clip-on verge instead of a mortar undercloak. They do not crack, they ventilate the roof properly, and they are what almost every new-build now uses. Where a traditional mortar look is wanted, or required in a conservation area, it can still be done as long as the mechanical fixing is there underneath.

Exposure decides how hard any of this is working. Temperature falls about half a degree per hundred metres, and the Met Office records materially more air frost on the high ground than on the Cheshire plain — Buxton averages 51.5 air-frost days a year against 40.0 at low-lying Woodford. Kerridge Hill is 313 metres and Shutlingsloe 506. Freeze-thaw on a mortar bed at that height is a different proposition to the same bed in Broken Cross.