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Capital Craft Construction
Brockley, SE4

Rear dormer loft conversion

A third bedroom and en suite built into an unused roof void, with the dormer designed to sit correctly on a tall villa in a conservation area.

Property
Mid-Victorian semi-detached villa
On site
11 weeks
A timber roof frame with hip rafters, new floor joists and a framed dormer box under a clear blue sky
The brief

A growing family in a two bedroom villa with a large and completely unused roof space. The constraint was the street: Brockley Conservation Area, tall houses, and a roof line visible from a long way down the road. A standard full-width box dormer would have been refused, and would have deserved to be.

What we did

A rear dormer set 500mm in from each party wall and 300mm below the ridge, with the cheeks clad in standing seam zinc rather than tile hanging. It reads as a considered addition rather than a bolted-on box, and it kept the application straightforward.

Structure

New floor joists spanning onto twin steels bearing on the party walls, so the new floor loads the walls rather than the ceiling below. The original lath and plaster ceiling downstairs survived the job intact, which does not always happen.

The staircase

The hardest decision in the project. Running the new flight over the existing stairwell would have cost the landing and made the second bedroom door unusable. We turned it through ninety degrees against the party wall instead, and found the head height with a small ceiling drop over the bottom three treads.

Fire and comfort

Fire doors to every room off the stairwell, mains-linked interlinked alarms and thirty minute floor construction. Insulated between and over the rafters with a ventilated void above, so the room is usable in July.

Behind the build

Process of work

The room was built inside an existing roof void, so nearly everything that decides how it feels was settled by the structure: where the dormer sits on the rear slope, how much of the original roof line stays visible in the room, and how low the window cill could be dropped off the new floor.

9 stages

  1. A new hipped roof covered in grey membrane and blue battens behind scaffolding, with a dormer on the rear slope and blockwork walls below

    01Roof felted and battened

    The new roof from the garden, wrapped in breathable membrane and battened ready for its covering, with the dormer sitting on the rear slope and the new blockwork walls rising below the scaffold.

  2. New timber roof rafters and hips standing on blockwork walls behind scaffolding, seen from the street against a blue sky

    02New roof timbers

    The roof timbers cut and fixed on top of the new walls, with the hip taking shape at the end and the frame for the dormer standing up behind it.

  3. A carpenter working on a new loft floor beside a timber-framed dormer, with the hipped roof covered in membrane and battens

    03Dormer framed, hip battened

    Up on the roof: the hip membraned and battened, the dormer framed in timber stud, and the new loft floor joists laid out across the top of the walls ready for boarding.

  4. New timber floor joists carried on red steel beams and columns inside a house under construction, with boarded walls and timber stacked on the slab

    04Steels and new joists

    Inside, the new floor joists are carried on steel beams and columns, so the weight of the new loft goes down to the foundations instead of onto the rooms below.

  5. A timber roof frame with hip rafters, new floor joists and a framed dormer box under a clear blue sky

    05Hips and dormer frame

    The full roof frame in daylight: hips and rafters cut in, the dormer box framed with its flat roof joists on top, and the loft floor joists running out across the walls.

  6. New rafters running up against an existing roof and brick chimney, with a timber stud wall for a dormer standing on the loft floor

    06Tying into the old roof

    New rafters tying the new roof into the existing one beside the chimney, with the dormer stud wall standing on the part-boarded loft floor.

  7. Inside a new roof structure with timber rafters, stud walls and membrane, above a boarded loft floor

    07Inside the roof

    Inside the new roof before insulation: rafters, stud partitions and the membrane behind them, showing the height the dormer gives across the new floor.

  8. Timber dormer walls framed on a new loft floor above red steel beams, beside two brick chimneys and a stripped-back roof

    08Dormer walls going up

    The dormer walls framed off the new floor, which sits on steels across the back of the house. The original chimneys stay, with the old roof stripped back beside them.

  9. Builders lifting a red steel beam into place on material hoists at the opened-up rear of a house, with the first floor propped above

    09Opening up the back

    Early in the job: the rear of the house opened up to first floor, the floor above propped, and a new steel beam lifted into place on hoists to carry the structure.

Outcome

A nineteen square metre double bedroom with an en suite shower room, and a roof line the conservation officer signed off first time.

More work

Other houses we have worked on

Next step

Tell us what you are trying to do with the house.

We will come out, measure up and tell you honestly whether it works. The site visit and the written quotation are free, and there is no obligation attached to either.

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