GS Renovation converts lofts across Morden, where 1930s suburban houses around Morden Hall Park make up most of the stock. In SM4 the roofs are usually high enough and the plots wide enough for a proper hip to gable and rear dormer. We coordinate the engineer, build the structure and see Merton Council building control through.
Getting the width back on an SM4 semi
The 1930s Morden roof is a hipped one, sloping in from the side as well as the back. That geometry wastes the part of the loft where the headroom is best, so the standard fix is to build the hip up into a vertical gable and then run a dormer across the rear. Between the two you get a full width double bedroom with an en suite, a landing and usable eaves storage rather than a cramped room with sloping walls on three sides.
This is proper structural work. The engineer specifies steel beams spanning from the party wall to the new gable, sized to carry both the new floor and the dormer above and bearing onto padstones. New floor joists sit clear of the existing ceiling joists, which were never designed to carry a floor. On indicative London ranges for 2026 a hip to gable with rear dormer sits at roughly £55,000 to £80,000, with an en suite adding £8,000 to £15,000.
Permitted development, tanks and Merton Council
Semi-detached and detached houses commonly have 50 cubic metres of added roof volume available under permitted development, and many Morden conversions sit inside it. The conditions still have to be met in full: materials matching the existing house, nothing forward of the roof plane on the elevation facing the highway, no balcony, and side facing windows obscure glazed and non-opening below 1.7m. Conservation area or Article 4 status removes the rights, so we check with Merton Council first.
One enabling step catches people out in 1930s houses. The old cold water tank usually sits exactly where the new bedroom goes, so it comes out and the system switches to a combi boiler or an unvented cylinder as part of the job. We plan that with the rest of the services, alongside the Part B fire protection to the stair, the Part K stair geometry and the insulation and ventilation that Merton building control will inspect.
- L-shaped dormers over a rear closet wing
- Velux and conservation rooflights fitted and flashed
- Hip to gable conversions on semi-detached and end terrace roofs
- Building control inspections booked at floor, steel and completion
- Trussed roofs redesigned before any web is cut
Why Choose GS Renovation in Morden
Morden homeowners choose GS Renovation because we handle the structure, the services and the finish as one job rather than three. Engineer coordination, steels, gable, dormer, tank removal, stair, insulation and decoration, with Merton Council building control carried to a completion certificate. Fully insured and building control compliant, with a dedicated project manager on site.
- Honest answer at survey if your roof will not take a conversion
- Photographs kept at each stage for your records
- Staircase set out to Part K within the space you have
- Ridge height measured before any design work is commissioned
- A dedicated project manager from first survey to handover
- Waste cleared as we go, not left piled in the garden