Permitted Development for Glass Extensions
2026 Updated Guide: What you can build without planning permission—and when you need to apply.
The Quick Answer (2026)
Most conservatories and glass extensions don’t need planning permission if they meet 2026 permitted development limits.
Detached houses: Up to 4m rear projection (8m with prior approval)
Semi-detached/Terraced: Up to 3m rear projection (6m with prior approval)
Maximum height: 4 metres overall
Maximum coverage: 50% of curtilage (including all extensions)
2026 Key changes: Planning application fee £572, Prior approval fee £260, LDC fee £290. Materials matching requirement relaxed for glass extensions.
Key exceptions: Listed buildings, conservation areas, flats, and properties with Article 4 directions may have restricted or removed rights.
Permitted Development Limits at a Glance (2026)
This comprehensive comparison table shows the 2026 permitted development limits for different property types. Use this as your quick reference guide when planning your glass extension.
| Requirement | Detached House | Semi/Terraced |
|---|---|---|
| Max rear projection (standard) | 4 metres | 3 metres |
| Max rear projection (prior approval) | 8 metres | 6 metres |
| Maximum overall height | 4 metres | 4 metres |
| Max eaves (within 2m of boundary) | 3 metres | 3 metres |
| Maximum curtilage coverage | 50% | 50% |
| Side extension width limit | 50% of original width | 50% of original width |
| Planning fee (2026) | £572 | £572 |
| Prior approval fee (2026) | £260 | £260 |
Detached Houses
Semi/Terraced Houses
2026 Key Regulatory Updates
Materials Matching Requirement Relaxed: The 2026 technical guidance specifically states that “the requirement for similar visual appearance does not apply to predominantly glazed structures.” This means your glass extension can use aluminium frames, uPVC, or timber without matching the brick or render of your house.
Fee Increases (Effective April 2026): Householder planning application: £572 (up from £528), Prior approval: £260 (up from £240), LDC: £290 (up from £264). These represent an average 8.3% increase to reflect inflation and administration costs.
Energy Efficiency Standards: Building Regulations Part L (Conservation of Fuel and Power) has been updated. While conservatories remain exempt if thermally separated, orangeries and open-plan glass extensions must meet enhanced U-values for glazing and insulation.
Frequently Asked Questions (2026)
Do I need planning permission for a conservatory in 2026?
Usually not, if your conservatory meets 2026 permitted development limits: maximum 4 metres projection for detached houses (3 metres for attached), maximum 4 metres height, positioned at the rear, and covering no more than 50% of the curtilage.
What is the maximum size conservatory without planning permission in 2026?
There is no absolute size limit in 2026. The limits are on projection (4 metres for detached, 3 metres for attached houses under standard PD), height (4 metres maximum), and curtilage coverage (50% maximum).
Do orangeries need planning permission in 2026?
Orangeries follow the same permitted development rules as conservatories in 2026. If they meet the size, height, and position limits, planning permission is not required.
Can I build a conservatory in a conservation area in 2026?
Yes, but with restrictions. Rear extensions not visible from a highway may still qualify under permitted development, though limits may be reduced.
What happens if I build without planning permission in 2026?
If your extension exceeds permitted development limits and you didn’t obtain planning permission, the council can take enforcement action.
How much does a Lawful Development Certificate cost in 2026?
An LDC for a proposed householder development costs £290 in England (from April 2026). This is half the cost of a full planning application (£572).
Ready to Discuss Your 2026 Extension Project?
Our 2026 planning specialists navigate permitted development rules every day. We work across London, Surrey, Sussex, Hampshire and the South East.
