Loft conversion in a 1930s semi

The brief

The house was a three bedroom semi built around 1934. The third bedroom was 2.1m wide, which is enough for a single bed and a chest of drawers and nothing else, so the two teenagers in the family were sharing the second bedroom and had been for two years. The parents had priced a rear extension, got a number back that was close to the loft figure, and decided they would rather keep the garden.

What they asked for was specific and short. A bedroom big enough for a double bed and a desk that a person could actually sit at. A shower room, because one bathroom for four people was the real daily problem. Somewhere to put suitcases and Christmas decorations, since the loft they were about to lose was where all of that lived.

What made it difficult

The roof measured 2.15m from the joists to the underside of the ridge. Building regulations do not set a minimum ceiling height for a loft room, which surprises people, but they do require 2.0m of headroom over the stair, and the pitch of a 1930s roof means that clearance runs out fast as you move away from the centre. Purlins sat at 1.4m above joist level on both slopes and took a large bite out of the usable width.

The landing below was the other problem, and the harder one. It measured 1.9m end to end. A conventional straight flight up to the loft would have consumed most of it and left the doors to two bedrooms opening into the bottom of a staircase, which is both unpleasant and, with a fire door requirement in play, awkward to detail.

Beyond that: a party wall to agree with the neighbours, a permitted development volume allowance of 50 cubic metres for a semi detached house that the dormer had to stay inside, an escape window on the new floor, and mains water pressure that was never going to run a shower two storeys up without help.

What we did

A box dormer across the rear slope, set 200mm down from the ridge and 200mm in from each party wall, which is what the volume allowance and the neighbours could both live with. That gave a flat ceiling across the back half of the room at 2.35m and a sloping ceiling at the front, which is a perfectly good place to put a bed.

The staircase rose over the existing flight with a three tread winder at the bottom. To make the winder work we borrowed 300mm from the built in cupboard in the second bedroom, which the family agreed to because the alternative was losing the landing. The top of the flight lands under the dormer where there is full height, so the first thing you meet at the top of the stairs is a room, not a slope.

The shower room went into the front slope where the head height was worst. The shower tray sits under the one section of full height we could give it and the basin and WC sit under the slope, where you are either sitting down or leaning forward anyway. A 1400mm run of eaves storage with plain painted doors took the suitcases.

Lighting was wall mounted rather than recessed. Downlights set into a sloping ceiling throw an oval of light onto the opposite wall and leave the room feeling like a corridor, which is a mistake we have seen in a lot of converted lofts. Two wall lights on the flat section and a reading light either side of the bed head do the job better and cost less. There is more on this in lighting a room in layers.

What it cost

Build cost landed at £44,800, inside a range we had given at the start of £41,000 to £48,000. The spread in that range was mostly about the shower room finish and whether the existing boiler could be kept, which it could.

On top of the build: our fee of £6,784, being a £3,200 design package plus project management at 8 per cent of the build cost, a structural engineer at £950 for the steels and the dormer, building control at £680, and a party wall surveyor at £1,100 because the neighbours appointed their own and the fees ended up with our clients, which is normal.

Three months of the programme were paper, not building. That is worth saying plainly, because people are often surprised at how much of a loft conversion happens before anyone arrives with a van.

What we would do differently

The staircase. We saved the landing, and the room at the top is genuinely good, but the three winder treads at the bottom are the one thing the family still mentions when we see them. Given the same house again we would test a straight flight taken 400mm further into the second bedroom before defending the winder, and we would put both options in front of the client as drawings rather than as a recommendation.