Flat roofing in Cranborne

Garages, garden rooms and the roof over an old bay. Village work in Cranborne is mostly small flat roofs attached to something older: a garage put up in the seventies, a garden room across the back, a porch, a boot room, and the little lead or felt roof capping a bay window.

The coverings in Cranborne are torch on felt, built up felt in three layers under a mineral cap sheet, tired GRP fibreglass, and now and then a genuine lead flat that has split along a bay. We strip a section and look at the deck first. Dry plywood or OSB can be re-covered as it stands. Chipboard decking that has drawn water is done for and new boards go down on the joists before anything else. Then it is EPDM rubber, fibreglass or a new torch on system, and single ply on anything with a long clear run.

Standing water and where it should be going. Ponding is the fault to look for first. Water that stays on a roof works into every lap and seam, and one hard frost opens them up. Usually the fall was never laid, the firrings have been cut too shallow, or the rainwater outlet has silted up under leaves from the trees around Cranborne. We reset the falls with firrings or tapered insulation so the roof drains at an outlet rather than in the middle, which is what BS 6229:2025 on flat roofs asks for, and we check the gutter, hopper and downpipe take it away cleanly.

The details that fail. The middle of a covering rarely gives trouble. The edge trim, the drip, the apron against a wall, the kerb around a rooflight and the laps are where water gets in. Felt goes as a blister, a bubble or a split. Single ply lifts at a failed seam. Fibreglass cracks at a hard internal angle. Failed material comes out first. The upstand is carried up behind the covering rather than stopped at deck level, and each lap is welded or bonded, so nothing is left relying on a repair over a repair.

Openings, abutments and the build up. Every rooflight, lantern, Velux, hatch and soil and vent pipe needs a kerb and a collar, not sealant. Where the roof meets brick or flint we chase in a cover flashing in lead, cut so it can move without splitting. On a parapet we look at the coping and whether a cavity tray sits behind it. Most of the older flat roofs in Cranborne are cold roofs, insulation between the joists with a still void above, and that void is where condensation and interstitial damp rot the deck out of sight. A warm roof turns that around. The insulation is laid over the boards on a vapour control layer, the void goes altogether, and the joists spend the winter dry.

Measure two flat roofs of equal size in Cranborne and their prices can still be far apart. The covering is quick. The rest is not.

The deck. Old garage roofs were often decked in chipboard. Once water gets in, it swells, sags and crumbles. Ply that springs under your boot is no better. Thomas lifts a corner before quoting, because a new deck changes the figure more than anything else.

The fall. A flat roof needs a slope you can barely see. Many older ones were laid level, or drain towards a corner where a later wall now stops the water. Firrings put the fall back. That takes time, and it stops the new membrane sitting in a puddle. Each upstand, edge trim and each of the outlets is costed individually.

Getting up there. A garage by a gravel drive needs only a tower. A roof under a bedroom window needs a scaffold that stays up for as long as the deck is open. The work at height rules say which, and the skip is listed apart.

Insulation. A full re-cover means insulating to current standard, so a warm deck is part of the price from the start.

Hold any other quote up to ours: which system and how many layers, a new deck or an overlay, and firrings to correct the falls or not.

Cranborne has its own conservation area, and there are a good many listed entries in and around the village, Cranborne Manor House among them. For flat roofing that has two practical consequences. The first is appearance. Putting like back for like is maintenance and needs nothing.

Changing what a roof looks like where it can be seen from the street or the green, adding a lantern or a run of rooflights, or fitting a bright trim in place of a dark one is a planning conversation, and it is far cheaper to have it before the order goes in.

The second is consent. If the building is listed, or your flat roof is on something attached to a listed building, changing the material or the look of the roof needs listed building consent, which is separate from planning permission. It is worth asking the council even about repairs, because the test is whether the work affects the building's character. Where an old lead flat is being replaced on a listed building, expect to be asked to put lead back rather than a modern membrane. For an ordinary house in Cranborne none of this bites, and the only real decision is which covering suits the roof.

Cranborne lies 13.9 miles from our Boscombe base. Our flat roof work covers the village, Boveridge, Alderholt and the BH21 lanes between them, and any building notice for a re-cover goes to Dorset Council.

The company is Bournemouth Roofing & Building Ltd, registered in England and Wales, company number 15471719, and Companies House will show you its record. Thomas Hannen owns it. He comes to walk the roof and he writes the price. On Checkatrade, one customer whose job was verified scored us 10 out of 10. The visit is free of charge, as is the itemised written quote. Before you book a visit in Cranborne, you can read our customers' Google reviews, word for word, on our reviews page.

Most repairs in Cranborne need no application at all. What decides whether a change to the outside of your house does is who the council is, whether a conservation area or a listing applies, and whether the place sits in a protected landscape.