Garden rooms, sheds and outbuildings

Four things, and none of them is the cladding you see in the photographs. The base comes first. A timber floor sitting on blocks in wet ground will rot, sag and fill with condensation, so we pour a reinforced slab with a damp proof membrane under it, or set piles where digging would wreck the garden. Second, the build up of the wall and roof. A garden office needs insulation between and over the studs, a breather membrane outside and a vapour control layer inside, taped. Get the layers the wrong way round and you get a room that streams with water every cold morning, which is the single most common fault we are called out to fix in other people’s garden rooms. Third, power. A room with an extension lead run out a kitchen window is a fire waiting to happen and will not take a heater, a kettle and a computer at once. The right answer is armoured cable buried at depth from the house board to its own small consumer unit in the room, with sockets, lights and an outdoor point, all certified. Add data while the trench is open, because running a cable later costs the same as the cable plus a second trench. Fourth, heating and glazing. A well insulated room of fifteen square metres needs very little heat, usually one electric panel or a small air to air unit, but it needs shade and ventilation just as much, since a glass fronted room facing south is unusable in July without an opening window or two. On the outside, larch and cedar weather to silver and need nothing but time. Painted composite and metal stay the colour you chose. Both outlast the felt roof on a flat pack shed by decades.

Where exemption usually sits

A domestic outbuilding behind the house, under twenty five square metres, low enough at the eaves and the ridge, and leaving at least twenty five square metres of private open space behind the house, is generally exempted development. It cannot be used as a separate dwelling, it cannot go in front of the building line, and previous sheds and extensions eat into the same allowance. We measure the garden and what is already in it at the survey and tell you where you stand before anything is ordered.