Roofing in Lytchett Matravers

Failed plastic dry verge on the newer estates. The three in ten houses here that went up between 1983 and 2008 got the first generation of plastic dry verge and ridge units, and that early plastic has gone brittle and chalky in the sun. Clips snap, a unit lifts in a gale, and the run unzips itself down the gable. It is replaced with current dry fix components screwed onto a ventilated roll, the mechanical fixing BS 5534 expects.

Mortar ridge and verge on the older estates. Over four in ten houses in the village date from 1945 to 1982 and none of them got dry fix at all. Ridge tiles bedded in sand and cement crack along the joint, the verge undercloak drops away, and the tiles start to rock. Strip the mortar, screw the ridge and verge down dry, and vent the roof space along the ridge while the fittings are off.

Concrete tile, mostly interlocking, covers most of the village. The cottages and older houses in the middle carry plain tile, clay tile and natural slate on battens with no sarking board behind them, so a slate roof there hangs on its nails alone.

A lot of the eighties and nineties houses had a rooflight or a loft conversion put in later, and the old flashing kit perishes at the apron and the side soakers. Where the nails, battens and underlay have gone together the covering comes off, soft rafter feet are cut out, and a new roof goes back on breathable membrane and treated battens. Garages and rear extensions in felt, GRP fibreglass or EPDM rubber, deck first. Chimney flashings, soakers and abutments in code rated lead, and the mortar fillets common on the older cottages crack every time. With the covering off, insulation and eaves ventilation are cheap to sort, and Approved Document L sets the standard a renovated roof is expected to reach.

No rate per square metre. Getting to it is most of it. Most of the village has a drive and a verge, so a scaffold and a lorry can usually get close, and the older lanes in the middle are the exception. The ground is cohesive and holds water through the winter, so a platform wants sole boards rather than standing on a soaked lawn. This is work at height and the work at height rules are why the platform is a priced line. Comparing quotes, ask whether the scaffold is in and who pays for the skip.

The village sits on cohesive ground with a real shrink and swell rating, which means it takes up water in winter and gives it back in summer, and the buildings on it move a little with the seasons. That is normal and it is not usually a defect. What it does change is which parts of a roof age fastest.

Rigid, bedded details are the ones that feel it: the mortar joint along the ridge, the flaunching around a chimney pot, the cement fillet where a lean-to meets a wall. They crack sooner here than on free draining ground, which is a straightforward argument for screwing the ridge and verge down dry instead of bedding them back in the same mortar for the third time.

It also changes where roof water is allowed to go. Repeatedly soaking cohesive ground beside a foundation is worth avoiding, so a downpipe wants to discharge into a proper gully and a drain, and not onto a border against the wall. If there are mature trees close to the house, get the rainwater run right before you worry about the roof covering. Approved Document H covers where the water is allowed to end up.