How far can you extend without planning permission?

As you consider adding extra living space, a home office, or perhaps extending your kitchen, one of the most common questions is: how far can you extend without planning permission? Understanding the rules around permitted development (PD) rights in the UK is essential to avoid unexpected costs, enforcement notices, or even the need to demolish unauthorised work. This guide dives into the limits, conditions, and best practices for extending your home without applying for planning permission.

What Are Permitted Development Rights?

Permitted development rights allow homeowners to make certain types of improvements without submitting a full planning application to their local authority. These rights are automatically granted under planning legislation, but they come with strict conditions and limits. Exceeding those triggers the need to apply for planning permission.

Key benefits of permitted development rights:

• Faster approval process
• No planning application fees
• Reduced risk of delays

However, some properties (listed buildings, conservation areas, and designated sites) may have restricted or removed PD rights. Always check with your local planning authority before proceeding.

Rear Extensions: Maximum Depth Limits

One of the most popular types of home extension is a rear extension, especially for kitchens and family rooms. Current PD rules for rear extensions typically allow:

• Detached houses: Up to 8 metres in single-storey depth
• Semi-detached and terraced houses: Up to 6 metres in single-storey depth

If your plans exceed these depths, you must apply for planning permission. Note that two-storey extensions and loft conversions have separate rules.

Side Extensions: Permitted Dimensions

Extending to the side of your house can maximise your plot width. Under permitted development, side extensions must adhere to:

• Single-storey side extensions: Maximum height of 4 metres, width no more than half the original house width
• Must not include verandas, balconies, or raised platforms
• Materials should match the existing house

Single-Storey vs Two-Storey Extensions

While single-storey extensions enjoy more generous PD rights, two-storey extensions face tighter restrictions:

Single-Storey

• Maximum height: 4 metres
• Depth limit: 6 metres (terraced/semi) or 8 metres (detached)
• Roof pitch must match existing house

Two-Storey

• Maximum eaves height: equal to existing eaves
• Maximum ridge height: no higher than existing roof
• Rear extensions: maximum depth of 3 metres (both detached and semi/terrace)

Exceeding any of these limits requires planning permission.

Conditions for All Permitted Development Extensions

Regardless of extension type, certain conditions apply to all PD rights:

1. Location
   • Not allowed forward of the principal elevation (i.e., cannot extend in front of the house)
2. Materials
   • Must be similar in appearance to the existing property
3. Site Coverage
   • Extensions cannot cover more than 50% of the total area around the original house
4. Designated Land
   • In conservation areas, national parks, or Areas of Outstanding Natural Beauty (AONB), PD rights are more limited

Prior Approval Process

If your project exceeds PD limits but still falls within certain tolerances, you may seek a “prior approval” rather than full planning:

• Submit details to local planning authority
• Address specific issues (e.g., flooding, highways impact, noise)
• Authority has 56 days to decide

Prior approval is quicker and less costly than full planning permission, but you must still meet the criteria set out in the Town and Country Planning (General Permitted Development) Order.

When to Apply for Planning Permission

You must apply for planning permission if your proposed extension:

• Exceeds PD size limits (depth, height, or volume)
• Extends forward of the principal elevation
• Covers more than half the garden/grounds
• Involves cladding with non-matching materials
• Is on designated land without specific PD allowances

Planning applications typically take 8–13 weeks to decide and involve fees, neighbour consultations, and sometimes design amendments.

Tips to Maximise Permitted Development Potential

1. Measure Carefully – Double-check your property’s footprint and boundaries.
2. Check Official Guidance – Refer to your local council’s planning portal and the government’s PD technical guidance.
3. Use a Professional – Architects and planning consultants can produce PD-compliant drawings and handle the prior approval process.
4. Inform Neighbours – Even if PD rights apply, keeping neighbours in the loop reduces objections and complaints.
5. Maintain Design Consistency – Matching roof pitch, brickwork, and window styles can help your PD application sail through.

Common Pitfalls to Avoid

• Assuming all homes have the same PD rights—some estates remove these rights by Article 4 Direction.
• Overlooking the 50% garden coverage rule—combining sheds, extensions, and decking can push you over the limit.
• Ignoring the finer details—small balconies or raised platforms require planning permission even if the extension itself is within PD limits.
• Forgetting Party Wall considerations—extensions close to shared boundaries need separate party wall agreements.

Conclusion

Knowing how far you can extend without planning permission empowers you to make the most of your property while avoiding regulatory headaches. Whether you’re adding a kitchen extension, home office, or a sunroom, staying within permitted development limits for depth, height, and site coverage ensures a smoother building process. If your project edges beyond these limits, consider the prior approval route or apply for planning permission well in advance. Always consult your local planning authority or a professional to confirm PD rights on your specific property before breaking ground.