Basement Finishing near you

Paragraph 2.16 of Approved Document B volume 1, the 2019 edition, is short and it governs the whole design. Basement storeys containing habitable rooms should have either an emergency escape window or external door providing escape from the basement, or a protected stairway leading from the basement to a final exit. Those are the two routes, and which one you can achieve depends entirely on the building rather than on the budget.

The window route is the cheaper one and it is often impossible below ground, because paragraph 2.10 describes what an emergency escape window has to be. The unobstructed openable area must be a minimum of 0.33 square metres, with a minimum height of 450mm and a minimum width of 450mm, and the bottom of the openable area a maximum of 1100mm above the floor. The person escaping must be able to reach a place free from danger from fire, so a window into a sealed lightwell with no way out of it does not qualify. The window has to stay open without being held, and locks and opening stays with child-resistant release catches are permitted.

The protected stairway route means the stair from the basement is separated by fire resisting construction at all storeys and runs to a final exit, which in most terraces means enclosing the existing cellar steps and the hallway above them with fire doorsets. That is structural and joinery work in the rest of the house rather than in the basement, and it is the item most often missing from a finishing quotation. Approved Document B is guidance for England; Wales, Scotland and Northern Ireland publish their own.

In a cellar the finished ceiling height is the output of every other decision rather than an input to them. A drained cavity floor membrane, the screed or boarding over it, insulation beneath that, and any pipework or drainage falls in between all stack up from the existing slab. At the other end, a fire resisting ceiling, service runs, downlight boxes and the depth of any new steelwork come down from the underside of the existing joists. Two contractors quoting on the same cellar can differ by a surprising amount in the height they leave you with, and the only way to compare them is to make each state the finished floor-to-ceiling dimension in writing.

The stair is where the height you have left becomes a legal question rather than a comfortable one. Stair geometry - rise, going, pitch and headroom over the flight - is set out in Approved Document K and is covered in our joinery and interior trim guides rather than here. The point specific to a basement is that a stair cannot simply be made steeper to claw back height: whatever comes off the ceiling of the room also comes off the headroom over the flight that reaches it.

The waterproofing decision sits behind all of it and is not a finishing decision. Below-ground waterproofing in Britain is a designed system under BS 8102, described in our water ingress guide, and finishing work should be specified around a waterproofing design that already exists. Fixing battens, dabbing plasterboard or drilling for sockets through a membrane somebody else guaranteed is the most reliable way there is to turn a dry basement into a wet one.

The commonest failure is not water coming through a wall. It is warm, humid air from upstairs meeting the coldest surfaces in the house and condensing on them, which arrives as a musty smell and black spotting in the corners rather than as a puddle. A cellar that was fine while it was full of moving air can become a problem the week it is sealed, insulated and given a door at the top of the stairs. Continuous background ventilation matters more here than anywhere else in the building.

The second is the pumped waste. A shower room below drain level depends on a pump, and a pump is a machine in a cupboard that eventually fails. Service access, an audible alarm somewhere a person will actually hear it, and a sensible decision about what is connected to it are all far cheaper to arrange at first fix than to retrofit through a finished ceiling.

The third is paperwork. A room finished without building control involvement is the item that stalls a sale, because there is no completion certificate to hand over and the buyer's surveyor can see a room the drawings do not show. Where the work was done years ago by somebody else, a regularisation application to the local authority is the route, and it is much easier to discuss before you start finishing over what they did.

The variables that move a fit-out price are the escape arrangement and whether it forces work into the rest of the house, the headroom you start with and how much of it the floor and ceiling build-ups take, whether the waterproofing design already exists or has to be commissioned, how far the waste has to be pumped and to where, the number of separate rooms being formed below ground, access for materials through a narrow hallway or a coal chute, and the standard of finish in a space where nothing is square. A cellar with a protected stairway already in place and a metre of spare height is a different job from an identical cellar with neither.

LokalMatch is the introduction and nothing more. Set out the basement once - what is down there now, what you want it to become, and your postcode - and contractors working in your area respond to you directly. Using LokalMatch costs homeowners nothing; the pros pay for the enquiries they receive. LokalMatch does not carry out the work, does not set prices and does not vet, rank or recommend anyone, so the checks on experience, insurance and waterproofing credentials remain yours to make.