Flat roofing in Broadstone

Small roofs, quick jobs. A garage, a porch or the flat top over a bay window is normally a single day. Most are felt, either a three layer built up system finished with a mineral cap sheet or a single torch on layer stuck over the last one. When the surface has gone brittle you get splits at the creases, blisters where damp was trapped, and a lifted seam at the back upstand. We strip to the deck and lay EPDM rubber in one piece, which leaves no lap and no seam anywhere in the open field of the roof.

Bigger roofs and awkward shapes. GRP fibreglass earns its place where a roof has kerbs, upstands and corners to work round, because it is laminated in place and every detail is part of the same skin. Single ply is hot air welded rather than bonded and suits a long run over an extension.

Deck, joists and falls. Under the covering is plywood, OSB or chipboard decking. Wet chipboard swells and gives underfoot and has to come off. The joists usually survive, and the firrings on them are what create the fall towards the outlet. Where the falls cannot be rebuilt in timber we form them in tapered insulation. Ponding, that flat sheet of standing water sitting a week after the rain, is the symptom of getting this wrong. BS 6229 covers how the falls and the drainage should be set out.

The insulation question. A sun lounge, a kitchen extension or a room in the roof all count as heated, so Part L expects the insulation to come up when the covering is renewed. Above the deck, sitting on a vapour control layer with PIR taking the thickness, keeps the timber warm. Between the joists leaves the deck on the cold side of the dew point, invites interstitial condensation into the build up, and rots it from within while the membrane above still looks perfect. We build the first kind. Building control are notified and inspect before it closes.

Junctions and openings. An abutment gets a chase cut into the wall and a lead cover flashing dressed into it, with a cavity tray over the top where the wall is cavity built. A parapet gets a coping and an apron beneath. Openings are formed on kerbs so the covering can turn up an upstand instead of stopping against a frame, and that goes for a rooflight, a lantern, a Velux style flat roof window, a loft hatch and a soil and vent pipe alike. The free edges finish on a drip trim, and the water leaves by a rainwater outlet into a hopper, a downpipe or the gutter. Extensions run to two or three working days, and we say how long before we start.

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 bungalow garage at the end of a drive, a flat roofed dormer on a chalet and a rear extension behind a semi are three different jobs before anything comes off. 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.

Broadstone drains slowly in heavy rain. The surface water risk across the area is on the high band, which you can check for your own postcode on the government flood risk service, and it changes one thing about a flat roof: the outlet is not a detail, it is the point.

A flat roof holds every drop that lands on it until the outlet takes it away. If that outlet is undersized, half blocked with moss, or discharging into a gully that is already backing up, the water sits on the deck and finds the first weak lap. So when we re-cover, we size the outlet for the area it serves, fit a leaf guard, and put in an overflow through the upstand so a blockage shows itself down the wall instead of soaking through your ceiling. We check where the downpipe actually goes too, because plenty round here discharge onto a path and straight back against the wall. Clearing the outlet twice a year afterwards costs nothing and prevents most of it.

We cover Broadstone, Corfe Mullen, Merley, Canford Heath and the rest of BH18. 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.