GS Renovation builds loft conversions in Mitcham, on the interwar semis and period terraces spread between Mitcham Common and Morden. The semis take hip to gable with a rear dormer; the older terraces suit a dormer over the back addition. We build to the engineer's design under Merton Council building control.
Two housing types, two loft answers in CR4
Mitcham's stock splits fairly evenly, and the right conversion follows the roof rather than the fashion. On a 1930s semi the hipped flank is the problem, and building it up into a gable before adding a rear dormer is what turns a triangular void into a room you can actually furnish. On the older terraces, where a rear closet wing survives, an L-shaped dormer wraps both slopes and gets a bedroom and a shower room out of a narrow plan.
Both routes start with the same check. From the top of the ceiling joists to the underside of the ridge you want roughly 2.2m to 2.4m, because the new floor sits above the old ceiling and the insulation eats into whatever is left. Indicative London ranges for 2026 put hip to gable with a rear dormer at roughly £55,000 to £80,000 and a plain rear dormer at roughly £45,000 to £65,000, with an en suite adding roughly £8,000 to £15,000.
Merton Council, party walls and inspections
Permitted development allowances are commonly cited as 40 cubic metres of added volume on a terrace and 50 on a semi or detached house, with conditions attached: materials to match, nothing forward of the existing roof plane, no balconies or verandas, and side windows obscure glazed and non-opening below 1.7m. Merton Council removes those rights inside its conservation areas and wherever an Article 4 direction applies, so we establish the position for your address before anyone commissions drawings.
Then come the regulations, which apply either way. Merton building control checks Part B fire safety, with a protected stair route to a final exit, fire doors and interlinked alarms; Part K on the stair; the engineer's steel and the new floor joists carried on it; and insulation and ventilation. Semis and terraces alike share a wall with a neighbour, so building a gable off it or bearing steel into it is notifiable, and the notice is served by you as building owner.
- Dormer cheeks, flat roof and leadwork detailed to last
- En suite plumbing, drainage and mechanical extraction
- Building control inspections booked at floor, steel and completion
- L-shaped dormers over a rear closet wing
- Protected stair enclosure and fire doors to Part B
The GS Renovation Difference in Mitcham
Mitcham homeowners choose GS Renovation because we start from what the roof actually is, not from a standard package. Hip to gable, dormer or rooflight, we coordinate the engineer, build the structure, fit the stair and en suite, and run Merton Council building control. Founder Abdelaaziz Saaid has 30+ years of hands-on experience, and we quote free of charge.
- Ridge height measured before any design work is commissioned
- Dust screens and floor protection in occupied homes
- Photographs kept at each stage for your records
- Roof type assessed so you get the scheme your house can actually take
- Aftercare and snagging support once the job is finished
- Honest updates if a date or a detail has to move