Flat roofing in Norton

The old flats. A Victorian back addition or a bay top was originally lead or zinc, laid over boards with rolls and drips. Lead splits where it was fixed too tightly to move, and it fatigues along a drip. Zinc goes at the pinholes. Where the original metal is still there and the building suits it, relaying in lead is the honest answer. Where somebody has already covered it in felt, we take the lot off and start from the deck.

The modern ones. Felt again: a three layer built up system with a mineral cap sheet, or a single torch on layer laid over the last covering. It splits at the creases, blisters where damp was sealed in, and lifts at a seam against an upstand. We put back EPDM rubber on a plain rectangle, bonded in one sheet with no lap in the open field, GRP fibreglass where there are kerbs and corners to laminate round, or single ply hot air welded on a longer run.

Deck, joists and falls. Modern decking is plywood, OSB or chipboard, and wet chipboard gives underfoot and comes off. On an older building the joists are rarely level to start with, so the fall has to be built rather than assumed, and that is what the firrings do. A roof holding standing water in the same corner has ponding, not weather, and it is what finishes a covering early. BS 6229 sets out falls and drainage, and where re-firring will not work we form the fall in tapered insulation.

Insulation on an old building. Over a heated room, Part L brings the insulation up when the covering is renewed. We take it above the deck: a vapour control layer first, PIR over that, then the membrane, so the timber never sits in cold damp air. The old cold roof arrangement, with insulation packed between the joists, leaves the boards under the dew point, and interstitial condensation forms inside the construction where nobody ever looks. On a solid walled house the junction with the wall wants particular care, which is what BS 5250 is about. Building control are notified and inspect it open.

Junctions and openings. An abutment on a modern wall takes a chase, a lead cover flashing dressed into it and a cavity tray above. Old soft brick and stone are better served by a stepped flashing worked into the existing joints. Parapets get a coping with an apron under it. Openings all stand on a kerb so the covering can turn up an upstand, which means a rooflight, a lantern, a Velux style flat roof window, a hatch and a soil and vent pipe. The open edges finish over a drip trim, and the rainwater outlet feeds a hopper, a downpipe or the gutter. A garage is a day, a back addition 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 lead flat over a back addition, a bungalow garage and a modern extension off a kitchen 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.

Norton has a lot of pre-1900 fabric, more than anywhere else we work. Those houses have solid walls that have to be able to dry out, lime rather than cement in the joints, and a back addition with a flat roof that was never designed around a plastic membrane. None of that stops you having a modern covering. It changes two details, and they are the two that get skipped.

The first is the abutment. Hacking a deep chase into soft old brick to take a cover flashing does more harm than good, so on the right wall we step the flashing into the existing joints instead and point it in lime. Cement over an old wall cracks within a few winters and then it leaks worse than before. The second is moisture. A warm roof laid tight against a solid wall can trap damp at the junction if the vapour control layer is taken to the wrong place, so we detail that properly and say on the quote how it is being done. Ask any other quote the same question.

We cover Norton, Yarmouth, Freshwater, Totland and the rest of PO41. 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.