Flat roofing in Winterborne Stickland

Start at the deck. Everything else follows from it. Lift a covering and you find plywood, OSB or chipboard decking laid over joists, with firrings on top forming the fall towards the outlet. Chipboard that has been wet for a season swells, gives underfoot and has to come off, and that is the biggest single swing in the price of the job. On an older building the joists are rarely level, so the fall gets built rather than assumed. Where re-firring will not work we form the fall in tapered insulation instead, and BS 6229 is where those falls come from.

Why they leak. Ponding first. A roof holding standing water in the same corner all winter is a roof with no fall, and it will finish a new covering as surely as it finished the old one. Then the covering itself: felt splits along the creases once it goes brittle, blisters where damp was sealed in underneath, and lifts at a seam where it turns up an upstand. A failed seam is the one that fools people, because water travels under the whole roof and comes through somewhere else entirely.

What we lay. EPDM rubber on a plain rectangle, bonded down in a single sheet with no lap in the open field. GRP fibreglass where there are kerbs, corners and upstands to laminate round, or where the roof gets walked on. Single ply, hot air welded, on a long run. Torch on felt, in a three layer built up system with a mineral cap sheet, still suits some buildings better than any of them.

Insulation, if the room below is heated. Renewing the covering brings it into scope under Part L. The insulation belongs above the deck, over a vapour control layer, in PIR, with the membrane on top. That is a warm roof and the whole structure stays on the dry side of the dew point. A cold roof, with the insulation between the joists, leaves the boards below it, and interstitial condensation forms inside the construction and rots them from above long before anything shows outside. Building control get notified and see it before it is closed up.

The junctions and the openings. This is the slow part of the job and the part that decides whether it leaks. A chase raked into the wall at the abutment, lead dressed in as a cover flashing, and a cavity tray above it, or a stepped flashing worked into the joints where the wall is old and soft. A coping on the parapet and an apron below it. A kerb under every rooflight, lantern, Velux style flat roof window, hatch and soil or vent pipe. A drip trim along the free edges. And a rainwater outlet running to a hopper, a downpipe or the gutter. A garage is a day, an extension two or three working days.

No rate per square metre, because the square metres are the easy part and what is under the covering is what decides the job.

Getting to it. A cottage with a small flat over a back addition, a detached garage on a modern plot and a kitchen extension across the back of a house are three different jobs before anyone unloads. A garage or a single storey extension will often come off a tower, anything above a two storey wall wants a scaffold, and the platform has to stand while the deck is open rather than for an afternoon. The work at height rules are why it is a priced line rather than something folded into a rate.

The deck under the covering. A sound deck can be re-covered. Chipboard that has been wet for years, or ply that gives underfoot, has to come off and be replaced, and you cannot tell which you have from the ground or from a photograph. We lift a corner before quoting, because the deck is the single biggest swing in the price.

The falls, and where the water is meant to go. Most flat roofs that fail were never laid to a fall, or the fall runs at an outlet that has since been blocked or built over. Correcting it with firrings is more work than laying a membrane and it is the difference between a roof that lasts and one that ponds. Upstands, edge trims and each outlet are priced one at a time, because that is where the hours and the leaks both are.

Comparing quotes? Ask which system is being quoted and how many layers, whether the deck is being renewed or covered over, whether the falls are being corrected with firrings, how the upstands, outlets and edge trims are detailed, and whether the scaffold and the skip are in the price. Two quotes for the same job are usually two different jobs.

Winterborne Stickland has a conservation area of its own, and there are a couple of dozen listed entries in and around the village. What people assume is that this covers everything. It usually does not. A village conservation area is normally drawn round the historic core, and plenty of houses on the edges sit outside it entirely.

That is worth ten minutes of your time before you order a roof, because the two situations are genuinely different. Outside the boundary, the covering on your garage or extension is your own decision and there is nothing to apply for. Inside it, appearance is controlled, so changing felt for a light coloured membrane, or putting in a rooflight or a lantern that can be seen, is something to agree first. Dorset Council hold the boundary maps and will tell you. Give us the address at the first visit and we will look at it with you, then put the position in writing next to the price so nothing depends on somebody's memory.

We cover Winterborne Stickland, Winterborne Whitechurch, Winterborne Houghton, Blandford Forum and the rest of DT11. You are dealing with Bournemouth Roofing & Building, the trading name of Bournemouth Roofing & Building Ltd, registered in England and Wales, company number 15471719, which you can look up in a minute. Thomas Hannen's business, and he is the one who comes out to price the job, not a salesman. A verified customer's 10 out of 10 on Checkatrade. The visit and the written quote are both free.