Permitted Development Rules for Extensions: What You Can Build Without Planning
The exact PD limits for single-storey rear extensions in England. Depth, height, curtilage, materials, and how to confirm your extension qualifies with a £274 Lawful Development Certificate.
Do this first:
Build a 3-metre rear extension on a semi-detached house in England and you don't need planning permission. Build it 3.1 metres and you might. Build it without checking, get it wrong by 10cm, and you could face an enforcement notice requiring demolition at your own expense. Or you only find out when you try to sell, and your buyer's solicitor refuses to proceed without proof that the extension was lawful.
Permitted development is not a free pass. It is a set of specific conditions, defined in legislation, that your extension must satisfy simultaneously. Every single one. Miss any condition and you are outside PD, which means you needed a planning application before you started and you didn't get one.
This guide assumes you've already worked through Do You Need Planning Permission? and established that your extension may fall within PD. If you haven't, start there.
This guide covers England only. Scotland, Wales, and Northern Ireland have different PD rules, different limits, and different fee structures. If your property is outside England, check with your local planning authority before relying on anything here.
The Seven Conditions at a Glance
PD rights for single-storey rear extensions fall under Schedule 2, Part 1, Class A of the Town and Country Planning (General Permitted Development) (England) Order 2015. There are seven conditions. All must be satisfied at the same time. If your extension passes six but fails one, you are outside PD.
| Condition | Requirement | Key Trap |
|---|---|---|
| 1. Property type | Must be a house (not a flat or maisonette) | Maisonettes look like houses but have no PD rights |
| 2. Depth | Max 3m (semi/terraced) or 4m (detached) from original rear wall | Measured from the original house, not the house as you bought it |
| 3. Overall height | Max 4 metres to the highest point | Measured from highest adjacent ground on sloping sites |
| 4. Eaves height | Max 3m within 2m of a boundary; cannot exceed existing eaves | Most semi/terraced extensions are within 2m of a boundary |
| 5. Curtilage coverage | Extensions must not cover more than 50% of the land around the original house | Cumulative: previous extensions and outbuildings count |
| 6. Materials | Must be of similar appearance to the existing house | Subjectively interpreted by each council |
| 7. No exclusions apply | Not a listed building, flat, or in an Article 4 area | Conservation areas, AONBs, and National Parks have extra restrictions |
The rest of this guide explains each condition in detail, then covers what happens when you exceed the standard limits, how to confirm your PD status, and what goes wrong if you get it wrong.
Condition 1: Property Type
PD rights for extensions apply only to houses (your property type matters). If you live in a flat or maisonette, any extension requires full planning permission regardless of size. This includes ground-floor flats with garden access. A maisonette can look like a house from the outside (it might even have its own front door), but it is legally classified differently. Check your property's title deeds if you are unsure.
Condition 2: Depth (How Far It Projects)
In planning terms, "depth" means how far the extension projects outward from the rear wall of the house into the garden. It does not mean how deep the foundations go into the ground. This is the first number people check, and the measurement most likely to cause problems.
| Property Type | Standard PD Limit | With Prior Approval | Planning Required |
|---|---|---|---|
| Detached house | Up to 4m from the original rear wall | 4m to 8m (neighbour consultation) | Beyond 8m |
| Semi-detached house | Up to 3m from the original rear wall | 3m to 6m (neighbour consultation) | Beyond 6m |
| Terraced house | Up to 3m from the original rear wall | 3m to 6m (neighbour consultation) | Beyond 6m |
The depth is measured from the rear wall of the original house, not from any existing extension or conservatory. This distinction matters enormously and is covered in detail under Condition 5.
Within the standard PD limits (3m or 4m depending on house type), you don't need to apply for anything. No planning application. No prior approval. You just build, provided every other condition is also met.
Between the standard limit and the enhanced limit (up to 6m or 8m), you enter the Larger Home Extension scheme, which requires a neighbour consultation process. See the Larger Home Extension Scheme section below, or read our dedicated Prior Approval guide for the full process.
Condition 3: Overall Height
Your single-storey extension cannot exceed 4 metres from ground level to the highest point of the roof. If the roof is pitched, the ridge counts. If it's flat, the parapet or highest edge counts.
If your garden slopes, this gets trickier. The rule says: find the highest point of ground where the extension will sit, and measure from there up to the roof. The direction of the slope determines whether this works for or against you.
Garden slopes downhill (away from the house). Say the ground drops 1 metre over the 3-metre depth of your planned extension. The highest ground is at the rear wall. If you design a flat roof at exactly 4 metres above that rear wall ground level, the official height is 4 metres and you are within the limit. The roof would appear 5 metres high from the lower ground at the far end, but that is not how the council measures it. A downhill garden works in your favour.
Garden slopes uphill (away from the house). Now the ground rises 1 metre over the 3-metre depth. The highest ground is at the far end of where the extension will sit. If you design the same flat roof at 4 metres above the rear wall, the official measurement is from the higher ground at the far end, giving a height of only 3 metres from that point. You are within the limit, but you have less usable internal height at the far end. Design a roof at 4 metres above the rear wall thinking you have headroom to spare, and you do. But if you designed the roof at 4 metres above the far end ground level, the measurement from that highest point would be 4 metres, putting you right at the limit, and the roof would actually be 5 metres above the rear wall ground. An uphill garden works against you.
Condition 4: Eaves Height and Boundary Distance
The eaves are the point where the external wall meets the underside of the roof. The eaves height and boundary distance interact as a combined condition. On a pitched roof, this is the bottom edge where the roof overhangs the wall. On a flat roof, it is the top of the wall where the roof structure begins.
If any part of the extension sits within 2 metres of a boundary (which it will on most semi-detached and terraced houses), the eaves cannot exceed 3 metres. This is measured from the ground on the side of the extension facing the boundary, not from the ground at the rear.
The extension's eaves must also not exceed the eaves height of the existing house. If your original eaves are at 2.5 metres, your extension eaves cannot go higher than 2.5 metres, even though the general PD limit is 3 metres.
Condition 5: Curtilage Coverage (The 50% Rule)
Extensions (including all previous additions to the original house) must not cover more than 50% of the curtilage area. Curtilage means the land around the original house, essentially your garden and any outbuildings.
This is a cumulative limit. If a previous owner built a conservatory that covers 20% of the curtilage, you've only got 30% left. If the house itself already occupies 40% of the plot, only 10% remains for any extensions before you hit the 50% ceiling.
On smaller plots, particularly terraced houses in urban areas, this rule bites harder than the depth limit. You might have room for a 3-metre extension by depth, but if the footprint pushes curtilage coverage over 50%, you're outside PD.
The curtilage and depth rules both depend on knowing what the original house looked like. PD limits are measured against the original house, which means the house as it was first built, or as it stood on 1 July 1948 for older properties. Not the house as you bought it. Not the house as it stands today.
If the previous owner added a 2-metre conservatory in 2003, that conservatory is already consuming your PD depth allowance. On a semi-detached house, your remaining PD depth would be 1 metre (3m total minus the 2m already used), not 3 metres. The conservatory also counts towards the 50% curtilage calculation.
Previous extensions count against your PD allowance and the allowance does not reset when the house changes hands. A former owner's conservatory, side return extension, or rear addition is eating into your limits. Always check the property's planning history with the council before assuming you have full PD rights.
To work out your curtilage coverage and check the original house, you need a site plan showing the plot boundary, the original house footprint, and all existing extensions. Your council's planning portal will have site plans from previous applications. You can also use the Google Earth timeline feature to view historic aerial imagery of your property, or order an Ordnance Survey map extract for around £10–40. Your council's online planning register will show any planning applications made against your address. If there is any doubt, an architect or planning consultant can research your property's history.
Condition 6: Materials
The extension's materials must be "of a similar appearance" to the existing house. On a red brick house, your builder uses matching red brick or a convincing match. On a stone cottage, matching stone or a render that closely resembles stone is required.
This is subjectively interpreted by each local planning authority. Grey render on a Victorian stone terrace is a grey area. Timber cladding on a 1930s pebble-dash semi might pass or might not, depending on the officer. There is no definitive national list of what qualifies as "similar".
If you're planning materials that differ from the existing house, check with your council first. A Lawful Development Certificate application will force a definitive answer. You want this clarified before you order materials, not after.
Condition 7: No Exclusions Apply
Several situations remove or restrict your PD rights entirely. If any of these apply, you need planning permission regardless of how small the extension is.
Listed buildings. PD rights do not apply to any external alteration of a listed building. You need both full planning permission and listed building consent. This applies to all grades: I, II*, and II.
Article 4 directions. Your council can remove specified PD rights for particular streets or areas. These are separate from conservation area restrictions and can apply anywhere. Check with your council's planning department whether one applies to your address.
Designated land. In conservation areas, Areas of Outstanding Natural Beauty (AONBs, now officially called National Landscapes), and National Parks, PD rights are restricted. Rear extensions may still be possible under PD but with tighter conditions. The Larger Home Extension scheme (prior approval for larger depths) is not available on designated land.
Side Extensions: A Separate Set of Rules
Everything above applies to rear extensions. Side extensions have their own, stricter PD conditions.
A side extension under PD must be single storey, must not exceed 4 metres in height, and its width must not exceed 50% of the width of the original house. That 50% width rule is separate from the 50% curtilage coverage rule, and the two are frequently confused.
If you want a full-width rear extension that wraps around the side of the house, the rear portion follows rear extension rules and the side portion follows side extension rules. Both sets of conditions must be satisfied. This interaction is genuinely confusing, and it's the kind of borderline case where an architect's or planning consultant's written opinion is worth the fee.
In conservation areas, AONBs, and National Parks, side extensions are excluded from PD entirely. You need planning permission.
The Larger Home Extension Scheme
If your rear extension exceeds the standard PD depth limit (3m for semi-detached/terraced, 4m for detached) but stays within the enhanced limit (6m or 8m respectively), you can use the Larger Home Extension scheme. This requires prior approval from your council.
Prior approval is not a full planning application. The council can only assess the impact on your immediate neighbours' amenity, specifically light and outlook. They cannot refuse on design grounds, character of the area, or any other planning policy consideration. But they can and do refuse on amenity grounds, and many councils apply the 45-degree rule informally when making this assessment.
The council has 42 days to make a decision. During that window, they must notify your adjoining neighbours and give them 21 days to respond. If the council fails to determine the application within 42 days, the prior approval is deemed granted by default.
If the council refuses, you can appeal to the Planning Inspectorate. Appeal success rates for Larger Home Extension refusals are among the highest for any planning appeal type, because councils frequently apply the wrong test.
For the full process, fees, timelines, and how to handle a refusal, read our dedicated guide: Prior Approval for a Larger Home Extension.
Confirm Your PD Status: Get a Lawful Development Certificate
A Lawful Development Certificate (LDC) is the council's written confirmation that your proposed extension is lawful under PD. Technically optional. Practically essential.
£274
The cost of a Lawful Development Certificate application in England. It gives you written certainty from the council that your extension qualifies as permitted development. When you sell, your buyer's solicitor will ask for it.
Without an LDC, you have no formal proof that your extension was lawful. When you sell, the buyer's solicitor will request planning evidence for any extension. If you can't produce an LDC or a planning approval, the solicitor will require either a retrospective LDC application (which takes weeks and may not succeed) or an indemnity insurance policy. Both delay the sale. Both add cost and stress at exactly the wrong moment.
Get the LDC before you build. Submit scaled drawings showing the proposed extension, your site plan, and evidence of the original house. The council will either issue the certificate (confirming PD applies) or refuse it (meaning you need planning permission). Either way, you have certainty.
What Happens If You Get It Wrong
If your extension breaches PD limits and you didn't apply for planning permission, the council can serve an enforcement notice requiring you to demolish the non-compliant parts, alter the extension to bring it within limits, or submit a retrospective planning application. A retrospective application is not guaranteed to succeed. If it fails, you're back to demolition or alteration, at your expense.
Even if the council doesn't actively enforce, the problem surfaces when you sell. A buyer's solicitor will flag the extension and demand evidence. Without an LDC or planning approval, the sale stalls. Some buyers walk away entirely.
Don't rely on verbal reassurance from a builder or an architect that "it's within PD". Architects are design professionals, not planning specialists. Builders are not planning specialists at all. The only opinion that counts is the council's, and the only way to get it in writing is through an LDC application. For borderline cases, a planning consultant's written assessment is money well spent before committing to a design.
Fees at a Glance
| What | Fee | When you need it |
|---|---|---|
| Lawful Development Certificate | £274 | Recommended for all PD extensions (proof for future sale) |
| Prior approval (Larger Home Extension) | £249 + £70 plus VAT | Extensions beyond standard PD depth limits (3-6m or 4-8m) |
| OS map extract | £10–40 | Needed if you don't already have a site plan |
| Planning consultant assessment | £100–300 | Borderline PD cases where professional opinion is needed |
PD Does Not Exempt You From Building Regulations
This catches people constantly. Building regulations and planning permission are completely separate systems. Even if your extension falls entirely within PD and you don't need a planning application, you still need building regulations approval for any structural work. Foundations, drainage, electrics, insulation, ventilation, fire safety: all require building control sign-off.
Read Building Control Notification for the full process and fees.
Pending Changes (2024 Consultation)
In February 2024, the government consulted on changes to PD rights including increasing standard depth limits to 5m (detached) and 4m (semi/terraced), allowing wrap-around L-shaped extensions under PD, and removing the 50% curtilage coverage limit. As of early 2026, the government has not published its response and no changes have been implemented. Plan on the basis of current rules, not proposed ones.
Your Next Steps
If you've confirmed your extension falls within PD limits:
- Get an LDC. Submit your drawings to the council and get written confirmation before you start.
- If you're between the standard limit and the enhanced limit, you need prior approval under the Larger Home Extension scheme. Read our dedicated guide and submit that application.
- Submit a building control notification regardless of PD status. Read Building Control Notification. PD doesn't exempt you from building regs.
- If you share a wall with a neighbour, start the party wall process. PD doesn't exempt you from the Party Wall Act either.
If your extension exceeds PD limits and doesn't qualify for prior approval, you need full planning permission. Read Submitting a Planning Application for the full process, costs, and timeline.
PD Compliance Checklist
10-point checklist covering every permitted development condition for single-storey rear extensions in England. Print it, check each item, and keep it with your project files.
Permitted Development Limit Checker
Enter your extension dimensions to check each PD condition individually. See which limits you pass, which you fail, and what your options are.