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Kitchen Extension Permitted Development: Rules and Costs
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.
Quick Answer
Kitchen extensions are permitted development if they meet the Part 1, Class A size limits
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.
PD Rules for Kitchen Extensions
| 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 |
Roof Options
- Flat roof with roof lantern: Very popular — brings natural light into what would otherwise be a dark rear room.
- Mono-pitch (lean-to) roof: Simple and weatherproof with a contemporary feel.
- Pitched roof: Matches house aesthetics, more expensive but more integrated.
- Glass/polycarbonate roof: Creates a bright, conservatory-like space.
Bifold and Sliding Doors
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.
Typical Kitchen Extension Costs
| 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 |
FAQs
Planning a rear extension?
Our Single Storey Rear Extension drawing package is pre-designed to the permitted development limits and supplied exactly as sold — £900 fixed price, emailed to you as a PDF.
See the Single Storey Rear Extension package →
Check my property and start my project · Read the rear extension rules
Planning a project? Browse our permitted development drawing sets — fixed price, supplied exactly as sold and emailed to you as a PDF.
Eight pre-designed projects.
Each one is already drawn. You choose the material, roof and options we actually draw, and that is the package you receive.

A practical entrance area that adds space and improves the look of your home.
£350
A popular way to create a larger kitchen, dining or family area.
£900
Adds valuable space to the side of your home for a kitchen or utility.
£900
Turns unused loft space into a bedroom, office or additional living area.
£1,500
A flexible, detached space for work, leisure or extra living space.
£350
Secure parking or useful storage, single or double.
£350
Significantly more living space across both floors.
£1,400
A bright, glazed room connecting your home to the garden.
£900









