One of the most common questions homeowners ask is whether they need planning permission for their extension. The good news is that many extensions fall under permitted development rights, meaning no application is needed.
Permitted Development Rules
For detached and semi-detached houses, you can typically extend:
- Rear extension: up to 4m beyond the rear wall (detached), or 3m (other houses) — single storey
- Rear extension height: maximum 4m
- Side extension: single storey, maximum width half the width of the original house
- No extension forward of the principal elevation
- Materials must be similar in appearance to the existing house
When you DO need planning permission
- Your extension exceeds permitted development size limits
- You live in a flat or maisonette (PD rights are more restricted)
- Your house is a listed building
- You are in a conservation area, Area of Outstanding Natural Beauty, or National Park
- You have already used your permitted development allowance
- The extension faces a highway and is over 1 storey
Prior Approval for Larger Extensions
Under the Neighbour Consultation Scheme, you can extend up to 8m (detached) or 6m (other) with prior approval. This involves notifying your local authority, who will consult neighbours. It is simpler than full planning permission.
Building Regulations
Even if planning permission is not needed, building regulations approval almost always is. This covers structural integrity, fire safety, insulation, damp proofing, and ventilation. Your contractor should handle this.