Rear extension + attic room

Brief

A 1950s semi-detached bungalow in Cheam (SM3) presented a classic suburban challenge: the owners needed both a larger kitchen-diner and an extra bedroom. The bungalow had a good ridge height (6.9m) making a vaulted attic room viable, and a 5m rear garden setback available for a rear extension. Combined brief: open-plan kitchen-diner extension at ground level and a vaulted attic room conversion at first floor.

Challenge

The 1950s bungalow had a narrow 3.2m-wide rear extension footprint available before hitting the 3m PD boundary (no planning required as semi-detached under the larger home extension scheme up to 6m). Phasing the works efficiently — structural roof work above whilst ground-floor extension was being built — required careful sequencing to keep the family in the property throughout with a weathertight kitchen at all stages. The attic room required cutting into the existing rafters and installing a steel ridge beam.

Solution

The rear extension was delivered under the Larger Home Extension prior approval route (6m depth, semi-detached) — no full planning application needed. A 6m × 4.2m rear extension on new strip foundations, cavity wall construction with grey brick to match the existing property, zinc standing seam roof with a 2.4m × 1.2m roof lantern. The attic room was formed by installing a 7.2m steel ridge beam, collar ties and two Velux FK06 rooflights. Both elements were built simultaneously with separate structural work stages — the family remained in the property throughout using a temporary kitchen in the dining room.

Outcome

The rear extension added 25.2m² of ground floor kitchen-diner space; the attic room added 18m² of first floor bedroom/office. The property effectively transformed from a 2-bed bungalow to a 3-bed house. Total floor area increase: 43m². Sutton Council prior approval received in 35 days. Post-completion estate agent estimate: £145,000 value uplift on £96,000 spend.