A 1930s semi reimagined — 62m² of new floor area downstairs and up, an open-plan kitchen-diner with full-width bi-folds, and a master suite with en-suite above.
When the Patel family bought their 1930s semi-detached in Didsbury, they had two children, a third on the way, and an unsalvageable galley kitchen squeezed into a 9m² rear lean-to. They needed space — and they needed it without leaving the catchment area.
Building Group was brought in after the family had already been quoted by two other contractors, both of whom had priced for a basic single-storey rear extension. We walked the site, measured up, and proposed something more ambitious: a rear-and-side double-storey extension that would solve the kitchen problem on the ground floor and add a master suite above — using the same scaffold, the same crew, and the same period of disruption.
The result is a home that has roughly doubled its functional family living space, retained its 1930s street-facing character, and added an estimated £185,000 to its market valuation.
The Patels had a clear list of needs and a much shorter list of wants. Their priorities, in their own order:
Budget ceiling was set at £150,000 including VAT, fixtures, and fittings. They were prepared to flex on internal finishes if it meant locking in the structural envelope at the right number.
Three things made this project more complex than the average rear extension:
The shared driveway gave us 1.1m of working width down the side of the property. Every load — steel, blocks, bricks, plasterboard — had to be planned for that pinch point. We staged deliveries in three phases instead of bulk-stocking on site.
A 12m sycamore in the neighbour's garden sat 6m from the proposed footprint. Tree Protection Order in force. We worked with a TPO-experienced arboriculturist on a Root Protection Area assessment and revised the foundation design to engineered-pile-and-beam to avoid root damage.
The street-facing 1930s bay was load-bearing and tied into the side wall we needed to break through internally. The structural engineer specified a goalpost steel frame to redistribute the load before we could form the rear opening. Sequencing mattered — one wrong order and the bay loses support.
The Patels lived on site throughout the build with two young children. We built a temporary kitchenette in the dining room, sealed the works area with dust-proof membrane each evening, and ran a strict 7:30am–5:00pm noise window with no Saturday work past 1pm.
We split the design into three integrated decisions that each unlocked the next.
Decision one — go up, not just out. Both alternative quotes had treated the master bedroom problem and the kitchen problem as separate future projects. Doing them in one mobilisation cut the combined cost by an estimated 22% versus phasing, and removed a second period of disruption from the family's life.
Decision two — piles, not strips. Conventional strip foundations would have meant excavating within the sycamore's Root Protection Area, which the council would not have approved. Engineered mini-piles tied to a reinforced ground beam let us transfer the load below the root zone with minimal disturbance. More expensive than strips by around £6,500, but the only viable route through planning.
Decision three — one steel ridge, not three lintels. The original concept had three separate lintels carrying the rear elevation. Our structural engineer redesigned it as a single continuous ridge beam, opening up an uninterrupted 5.4m glazed rear wall and removing the visual bulk of three lintel pockets. The bi-fold opening went from a planned 3-leaf to a 5-leaf as a result.
Eighteen weeks from first dig to handover. Here's how it ran:
Hoarding installed, scaffold erected, existing rear lean-to demolished and cleared. Welfare unit and tool store positioned at the rear of the side return. TPO sycamore root zone marked off with timber hoarding.
Twenty-two mini-piles driven to refusal at depths of 4.2–5.1m. Reinforced concrete ground beam poured and cured. Building Control attended for foundation inspection and signed off the substructure.
Cavity wall construction in concrete block inner / facing brick outer, matched to the original 1930s stretcher bond. Steel goalpost frame craned in and bolted to padstones. Internal blockwork to first floor level.
Engineered timber I-joists for the first floor, traditional cut-roof for the rear pitch with feature steel ridge. Slate tiles to match the original front elevation. Building reaches weathertight stage on day 62.
Full first fix: electrical, plumbing, underfloor heating manifolds and pipework, MVHR ducting to en-suite. Bi-fold door subframe installed. Thermal insulation to walls and roof to current Part L standards.
Two-coat plaster throughout, finished to matt-paint level. Heat pump hot water cylinder relocated to upstairs cupboard. Underfloor heating commissioned and pressure-tested.
Bespoke handle-less kitchen installed, quartz worktops templated and fitted on day 108. En-suite fully tiled and second-fix sanitaryware installed. Bi-fold doors hung and adjusted.
Final decorating coats, snagging walk-through with the family, Building Control completion certificate issued, FENSA certificates lodged. Keys handed back, project file delivered including 10-year structural warranty paperwork.
The technical detail behind the finished build.
22 no. mini-piles driven to refusal (4.2–5.1m), reinforced ground beam, designed for tree Root Protection Area compliance.
Cavity construction: 100mm Celotex PIR, 100mm concrete block inner, 102mm facing brick outer matched to original 1930s stretcher bond.
Traditional cut roof with structural steel ridge beam (203 x 133 UB), Spanish slate to match existing, lead flashings, GRP-lined valleys.
5-leaf aluminium bi-fold doors (5.4m total opening), thermally-broken frames, U-value 1.4 W/m²K, anthracite grey RAL 7016.
Wet underfloor heating downstairs (8 zones), traditional radiators upstairs, replacement Vaillant ecoTEC 35kW combi boiler with smart thermostat.
Full new circuit added, RCBO consumer unit upgrade, 14 no. downlights, integrated cooker hood extraction, Cat-6 data point to home office area.
Walk-in 1200mm shower, wall-hung WC, vanity unit with quartz top, full-height porcelain wall tile, MVHR extraction.
SAP-assessed energy rating uplift from D62 to B86, full Part L compliance, MVHR system extracting from kitchen and en-suite.
The Patels moved from a 4-bedroom semi with a cramped galley kitchen into a 5-bedroom family home with a 38m² open-plan kitchen-diner, a master suite with private en-suite, and a fully-glazed rear elevation overlooking the garden — all without changing schools, postcode, or street.
The completion certificate was issued on day 124, six days inside the contracted 18-week window. The final invoice landed at £147,840 against a fixed-price contract of £148,000.
We'd been quoted by two other firms before we found Building Group. The other quotes were for half the project and still cost most of what we ended up paying for the full job. The team turned up when they said they would, the price didn't move, and they were genuinely careful around the kids and the dog. We've got the house we'll grow old in.
If you're thinking about a single or double-storey extension on a 1930s, Edwardian or Victorian property, we'll come out for a free site visit and quote — fixed price, no surprises.
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