Quick summary: house extension planning permission
House extension planning permission is not required for every extension in England. Many rear and side extensions can fall within permitted development, but only where the proposal meets the relevant size, height, position and property restrictions.
- Some extensions can be built under permitted development without a full householder planning application.
- Rear, side and two-storey extensions have different limits, so there is no single maximum size that applies to every property.
- Front extensions are much more likely to need planning permission, particularly where they project forward of the principal elevation facing a highway.
- Conservation areas, Article 4 Directions and previous planning conditions can restrict or remove permitted development rights.
- Planning permission and Building Regulations are separate. An extension that does not need a planning application can still require Building Regulations approval.
Before building, check the planning history of the property, confirm what counts as the “original house”, and establish whether permitted development rights still apply. If there is any doubt, a Lawful Development Certificate can provide formal confirmation from your local planning authority.
Planning an extension but unsure which permission you need?
We can check the proposed size, position and planning history before you commit to drawings or building work.
When is house extension planning permission required?
Whether you need house extension planning permission depends on the property, the position of the extension and what has already been added to the original house. It is therefore better to check the proposal as a whole rather than relying on one measurement such as depth or floor area.
In England, permitted development rights give many householders the ability to extend without making a full planning application. However, those rights only apply where every relevant limitation and condition is satisfied.
Full planning permission is more likely to be required where an extension exceeds permitted development limits, projects from the front of the property, affects a restricted property or is in a location where permitted development rights have been removed.
If you want a broader overview before deciding what route applies, see our detailed extension permission checklist.
House extensions without planning permission: how permitted development works
“Without planning permission” does not mean “without rules”. Permitted development is itself a form of planning permission granted nationally, provided the development stays within the legislation.
Some of the main considerations include:
- how far the extension projects beyond the original house,
- its overall and eaves height,
- distance from boundaries,
- whether it is a rear, side or front extension,
- how much of the land around the original house is already covered,
- whether previous extensions must be counted, and
- whether the property has restricted permitted development rights.
What size house extension can you build without a full planning application?
Under the normal Class A permitted development limits, a single-storey rear extension can generally project up to 4 metres from the original rear wall of a detached house or 3 metres for other houses, subject to the other conditions.
A larger-home-extension process can potentially allow rear extensions of up to 8 metres for a detached house and 6 metres for other houses. However, this uses the prior approval process, so it should not be treated as an automatic right to start building.
A single-storey extension must also stay within the relevant height restrictions. For example, the overall height is generally limited to 4 metres, while eaves close to a boundary have a lower limit.
For a wider explanation of the national rules, see our homeowner breakdown of permitted development.
Rear, side and front house extension planning rules compared
Rear house extensions
Rear extensions are the most common candidates for permitted development. Nevertheless, depth, height, boundaries, previous additions and designated-land restrictions all need checking.
Side house extensions
A side extension under Class A permitted development must normally be single storey, no more than 4 metres high and no wider than half the width of the original house. Additional restrictions apply on certain designated land.
If you are comparing layouts, our rear-versus-side design guide explains some of the practical differences as well.
Front-of-house extensions
Front extensions are more restrictive. An enlargement extending beyond the principal elevation, or in certain circumstances a side elevation facing a highway, will not normally qualify under the standard Class A permitted development right.
Consequently, front porches and front extensions need to be assessed carefully rather than applying the rear-extension rules to them.
Terraced and semi-detached house extension rules
Terraced and semi-detached houses can benefit from permitted development rights, but their allowable rear-extension depth differs from the standard limit for detached houses. Boundary proximity and effects on neighbouring homes also tend to be more important because properties sit closer together.
For example, a terraced house extension may satisfy the permitted development depth limit but still need careful design around eaves, shared boundaries, drainage and the Party Wall etc. Act.
Not sure if your extension fits Permitted Development?
We’ll check your project against the relevant rules and explain whether you need permitted development confirmation, prior approval or a full planning application.
How to check house extension planning permission step by step
A sensible planning check should happen before detailed construction work is commissioned. That way, you avoid designing around assumptions that later prove incorrect.
House extension permission checklist
- Check the type of property. Confirm that the building is a house rather than a flat or maisonette.
- Establish the original house. Check historic plans and previous extensions rather than measuring only the present building.
- Review the planning history. Look for conditions that may restrict permitted development rights.
- Check the proposed position and dimensions. Measure depth, width, height, eaves and relationship to boundaries.
- Check local restrictions. Conservation areas, Article 4 Directions and other designations can change what is possible.
- Choose the correct planning route. This may be permitted development, prior approval or a householder planning application.
- Prepare accurate drawings. Existing and proposed plans and elevations make the proposal clear and measurable.
- Keep formal evidence. Where appropriate, consider a Lawful Development Certificate rather than relying only on an informal opinion.
If drawings are your next step, our guide to what should be included in an extension drawing package explains what homeowners should normally expect.
How much does planning permission for a house extension cost?
Quick costs snapshot
- Householder planning application in England: £548 from 1 April 2026 for enlargement, improvement or alteration of one dwellinghouse, excluding flats.
- Larger-home-extension prior approval: £249 from 1 April 2026.
- Professional drawings and planning support: separate from the council application fee.
- Specialist reports: may add cost where trees, heritage, ecology, drainage or other site constraints need assessment.
Planning fees are periodically updated, so check the applicable fee immediately before submission.
Straightforward householder planning applications are normally targeted for determination within eight weeks, although an authority and applicant can agree a longer period. In practice, validation issues, amended drawings or additional information can affect the overall timeline.
Our separate guides explain what happens during the council decision period and the other costs to allow for when budgeting.
Local council rules, neighbours and planning restrictions
National permitted development legislation applies across England, but that does not mean every house has identical rights. A planning condition attached to an earlier permission may remove particular rights, while an Article 4 Direction can restrict development that would otherwise be permitted.
Conservation areas and other designated land also have additional limitations. Meanwhile, where a full planning application is required, the council will assess the proposal against its development plan and relevant national policy, including matters such as design and neighbour amenity.
Neighbours can comment when they are consulted, but an objection does not automatically mean refusal. Equally, having no objections does not guarantee approval. The planning authority must make the decision against the relevant planning considerations.
For more detail on this point, read what neighbour objections can and cannot do.
Planning permission is not the same as Building Regulations
This distinction catches many homeowners out. Planning controls whether the development is acceptable from a land-use and design perspective. Building Regulations deal with how the extension is constructed safely and compliantly.
Therefore, an extension that falls entirely within permitted development can still require Building Regulations approval. Structural safety, insulation and energy efficiency, fire safety, ventilation, drainage and electrical work may all come into the Building Regulations process.
Before construction, see what Building Control is likely to check during an extension project.
Before you start your house extension
The safest approach is to establish the planning route before finalising the design. Start with the original-house dimensions and planning history, then check the national permitted development rules and any local restrictions that apply to your property.
Where the proposal clearly falls outside permitted development, prepare a well-considered householder application. Where it appears to comply, formal confirmation through a Lawful Development Certificate can give useful evidence for your records and for a future sale.
FAQs: house extension planning permission
What size extension can I build without planning permission?
There is no single size that applies to every extension. For a typical single-storey rear extension in England, the standard Class A depth limit is normally 4 metres for a detached house and 3 metres for other houses. Larger rear extensions may be possible through the prior approval route. Height, boundaries, previous extensions and other restrictions must also be checked.
What extension needs planning permission?
A full application is generally needed where the proposal does not comply with the relevant permitted development limits or where those rights do not apply. Front extensions, larger designs, certain extensions on designated land and properties with restricted permitted development rights commonly require closer assessment.
Do house extensions need planning permission?
Not always. Many house extensions can qualify as permitted development in England. However, permitted development comes with detailed limitations and conditions, so the proposal must be checked rather than assumed to be exempt.
Can I build a rear house extension without planning permission?
Potentially, yes. Rear extensions are commonly carried out under permitted development where the depth, height and other requirements are satisfied. Larger rear extensions can involve prior approval and neighbour consultation before work starts.
Can a terraced house be extended without planning permission?
Yes, a terraced house can benefit from permitted development rights where all the relevant conditions are met. However, the standard rear-extension depth limit for a terraced house differs from that for a detached property, and boundary issues usually need particularly careful consideration.
Do I need planning permission to extend the front of my house?
Front extensions are much less likely to qualify under the normal householder permitted development rules because development forward of the principal elevation is restricted. The exact proposal and relationship with the highway should be checked with the planning rules and your local authority.
Can neighbours stop my house extension?
Neighbours can make comments or objections where consultation takes place, but they do not normally have an automatic veto. The council considers relevant planning matters such as overlooking, privacy, daylight, outlook and design before reaching its decision.
Does a house extension need a building permit as well as planning permission?
In England the usual term is Building Regulations approval rather than a “building permit”. Most house extensions require Building Regulations approval even where a full planning application is not required.
Still not sure which route applies to your property?
A quick check now can prevent drawings, applications or building work being based on the wrong assumptions.
Next steps & useful guides
If you are moving from the planning stage towards drawings, costs or construction, these PME guides are useful next steps:
- Start with the complete homeowner guide to extending your house
- Use our detailed checklist before deciding which application route applies
- Understand the national permitted development framework
- See what should normally appear on your proposed plans
- Budget for application fees and associated professional work
- Understand the usual council decision process
- Prepare for the Building Regulations stage
- Understand how neighbour comments are considered
- Full planning always required? No. Some extensions qualify under permitted development rights.
- Standard rear depth Normally up to 4m for a detached house and 3m for other houses, subject to all other Class A requirements.
- Larger rear extension Potentially up to 8m detached or 6m for other houses using the relevant prior approval procedure.
- 2026 householder application fee £548 in England from 1 April 2026 for enlargement, improvement or alteration of a single dwellinghouse, excluding flats.
- Typical council target Straightforward householder applications are normally targeted for determination within eight weeks or an agreed extended period.
- Building Regulations Separate from planning and usually still relevant to an extension.
- Best evidence for PD Consider applying for a Lawful Development Certificate where formal confirmation would be useful.
Unsure which rules apply? Ask our team to review the proposed extension before you proceed.
Official guidance and further reading
Planning rules can change and individual properties can have additional restrictions. These authoritative sources are useful for checking the latest position:
- GOV.UK guidance on when planning permission may be required
- Government technical guidance explaining householder permitted development rights
- Ministry of Housing, Communities and Local Government planning application statistics
- Planning Portal practical guidance for domestic extensions
Ready to move your extension forward?
Plans Made Easy can prepare compliant plans, manage submissions, and guide you from your first idea through planning and Building Regulations.
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