Most kitchen extensions are permitted development if they meet the Part 1, Class A size limits. Here’s what the rules allow, the roof and glazing options, and typical costs.
A kitchen extension at the rear of a house can be permitted development under Part 1, Class A of the GPDO 2015. For detached houses, the standard PD allowance is 4m depth; for semi-detached and terraced houses, 3m. These can be extended to 8m/6m under the Larger Home Extension Scheme. The extension must be single storey, no higher than 4m, and not extend beyond the side elevation of the original house.
| Condition | Detail |
|---|---|
| Maximum depth (detached) | 4m (up to 8m under Larger Home Extension Scheme) |
| Maximum depth (semi/terrace) | 3m (up to 6m under Larger Home Extension Scheme) |
| Maximum height | 4m (3m if within 2m of boundary) |
| Width | Must not extend beyond the side elevation of the original house |
| Storey count | Single storey only |
| Materials | Must match the appearance of the exterior of the existing dwelling |
Bifold and sliding patio doors do not affect permitted development rights. The PD rules relate to the volume and position of the new structure, not the glazing details. You can install bifold doors, corner glass, or Crittall-style steel frames without affecting your PD rights.
| Item | Approximate Cost |
|---|---|
| Small kitchen extension (up to 12m²) | £15,000–25,000 (structure only) |
| Medium kitchen extension (12–25m²) | £25,000–45,000 |
| Large kitchen extension (25–40m²) | £40,000–70,000+ |
| Roof lantern | £2,000–6,000 |
| Bifold doors (3-panel) | £3,000–6,000 |
| New kitchen fit-out | £10,000–30,000+ additional |
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