Flat roofing in Ashley Heath

Garage and outbuilding roofs. Most are felt, either a three layer built up system with a mineral cap sheet or a single torch on layer laid over whatever was there before. Once the surface goes brittle you get splits along the joints and blisters where damp has been trapped underneath. On a small square roof we take it back to the deck and lay EPDM rubber in one piece, so there is no lap and no seam in the open part of the roof at all. GRP fibreglass suits roofs with more shape to them, because upstands and kerbs are laminated in place rather than bonded on afterwards. Single ply is hot air welded, which beats a torch beside a timber wall.

Under the covering. Lift it and you find plywood, OSB or, on the older ones, chipboard. Chipboard that has been wet swells, gives underfoot and has to come off. The joists are usually sound and the firrings on top of them are what create the fall. Plenty of these roofs were laid dead flat, which is where ponding starts, and standing water in the same corner all winter finishes a covering off years early. Where the joists cannot be re-firred we build the fall in tapered insulation instead. BS 6229 sets out how a flat roof sheds water.

Rooms you live in. A roof over a kitchen or a bedroom is a different animal to a garage. Renewing the covering brings the insulation into scope under Part L, so the build up becomes a warm roof: a vapour control layer on the deck, PIR boards over it, membrane on top. A cold roof, with the insulation pushed down between the joists, is the one that causes grief, because moist air reaches the dew point inside the construction and interstitial condensation rots the deck from above. Building control want that done properly and we notify them.

Edges, junctions and openings. At the abutment we cut a chase and dress in a lead cover flashing, and on a cavity wall a cavity tray sits above it or water tracks down inside. A parapet needs its coping and an apron. Rooflights, a kitchen lantern and a Velux style flat roof window all sit on a raised kerb rather than flat on the deck, and so does a hatch or a soil and vent pipe. Free edges take a drip trim, and the rainwater outlet runs into a hopper and downpipe or a fall into the gutter. Dormer cheeks and bay tops on the bungalows here leak out of all proportion to their size.

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 on a bungalow, a rear extension on a chalet and a dormer cheek on a two storey house are three different propositions before anyone opens a roll of anything. 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.

Ashley Heath sits open, and the elevation that takes the worst of it faces south west. On a pitched roof that shows up as moss and slipped tiles. On a flat roof it does something more specific. Wind gets under the perimeter, lifts the covering at the edge trim and works its way in from there. Nearly every flat roof we have seen fail early failed at a corner or along a windward edge, not out in the middle.

So the perimeter is where the care goes. Fixings at closer centres along the exposed edges, the trim screwed down properly rather than nailed through the covering, and upstands taken high enough that driven rain cannot get behind them. It adds very little while the roof is open, and it decides whether the covering sits there quietly or starts flapping in the first proper south westerly. If you are collecting quotes, ask what the edge detail is.

We cover Ashley Heath, Ashley, St Leonards, St Ives and Ringwood, and the rest of BH24. 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.