Flat roofing in Spetisbury

What is up there now. Felt, nearly always. Either a three layer built up system finished with a mineral cap sheet, or a single torch on layer laid straight over the covering before it. It gives up in three ways: splits along the creases where the sheet has been folded, blisters where damp was sealed in underneath, and a lifted or failed seam where the covering turns up an upstand. The last one is the worst, because water then travels under the whole roof.

What we put back. EPDM rubber on a plain rectangle, bonded down in one sheet so there is no lap or seam anywhere in the open part of the roof. GRP fibreglass where a roof has kerbs, corners and upstands to laminate round, or where somebody will walk on it. Single ply, hot air welded, on a longer run.

The deck and the fall. Under the covering is plywood, OSB or chipboard decking on joists, with firrings on top making the fall towards the outlet. Chipboard that has been wet swells, gives underfoot and has to come off, and it is the single biggest swing in the price. A roof laid dead flat holds standing water, and ponding in the same corner every winter will finish a new covering as surely as it finished the old one. BS 6229 sets out the falls, and where re-firring will not work we form them in tapered insulation.

Heated rooms need the insulation moving. Renewing a covering over a kitchen or a bedroom brings the insulation into scope under Part L. On a flat roof the right place for it is above the deck, on a vapour control layer, in PIR, with the membrane over the top. That is a warm roof, and everything structural stays dry. The old cold roof, insulated between the joists, puts the boards below the dew point, so interstitial condensation forms inside the build up and rots them from above while the covering still looks sound. Building control are notified and inspect it open.

Edges, junctions and openings. These take the time, and they are the parts a cheap quote leaves out. A chase raked into the wall at the abutment, lead dressed into it as a cover flashing, a cavity tray above it. A coping on the parapet with an apron below. A kerb under every rooflight, lantern, Velux style flat roof window, hatch and soil or vent pipe, so the covering turns up an upstand. A drip trim on 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, and we say how long first.

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 detached garage at the end of a drive, a porch roof over a front door and a rear extension behind a semi are three different jobs before anything is unloaded. 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.

Plenty of Dorset villages come with a conservation area over the housing and a long list of controls on what a roof can be. Spetisbury does not. For most addresses in the village there is nothing to apply for and nobody to satisfy on appearance, which means the covering on your garage or your extension is genuinely your decision.

That freedom is worth spending in the right place, and it is almost never on the covering itself. A premium membrane laid over a soft deck and a fall that goes nowhere will fail on the same timetable as a cheap one. So if there is money to put anywhere, put it into replacing tired decking, into firrings that give the roof a real fall, and into a properly sized outlet with somewhere for the water to go. Then pick the covering that suits the shape of the roof. We quote it that way round, with the deck and the falls as their own lines, so you can see exactly what you are buying and what you are choosing to leave.

We cover Spetisbury, Charlton Marshall, Sturminster Marshall, 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.