Overview
Single-storey extensions can be up to 8m deep for detached houses, or 6m for others.
The key rules for permitted development:
- Must not cover over half the garden.
- Height restrictions apply.
Can I build an extension without planning permission?
The answer is yes, subject to a few terms and conditions…
The addition of a new building on your land may seem like a good idea initially but when you delve deeper into the regulations, the red tape surrounding planning permissions can become rather complex. However, since permitted development rights were extended in 2013 under the Larger Home Extension Scheme, it’s hardly surprising that architects, builders and double-glazing companies across England have experienced a considerable boost in demand for single-storey extensions and conservatories in conservation areas. This is why we thought it the perfect time to explain exactly how big a building can be without the need for planning permission, including conservation areas.
PD Limits – Key Facts & Figures
Use this quick reference, then see detailed rules below. Figures here are typical PD limits—always verify against your local authority guidance and any Article 4 directions.
| Scenario | Max rear extension depth (standard PD) | Max rear extension depth (Larger Home Extension*) | Max height | Eaves near boundary | Notes |
|---|---|---|---|---|---|
| Terraced House (non-conservation area) | 3 m beyond original rear wall | Up to 6 m via neighbour consultation* | 4 m overall; not higher than existing roof | ≤ 3 m if within 2 m of boundary | Houses only (not flats/maisonettes). Check Article 4 directions. |
| Semidetached (non-conservation area) | 4 m beyond original rear wall | Up to 8 m via neighbour consultation* | 4 m overall; not higher than existing roof | ≤ 3 m if within 2 m of boundary | Subject to design/amenity checks under the consultation. |
| House — conservation area | Typically 3 m (attached) / 4 m (detached) under standard PD | May be restricted by designated-land rules or Article 4* | 4 m overall (usual PD limits) | ≤ 3 m if within 2 m of boundary | Always confirm with local authority; conservation status and Article 4 can remove/limit PD rights. |
What size extension can I build without planning permission?
So, how big can I extend my home without planning permission? Well, single-storey extensions, e.g. conservatories and orangeries, are covered by permitted development rights as long as:
- Attached property extensions do not extend beyond the rear wall of the original home by more than 3 metres.
- Detached property extensions do not extend beyond the rear wall of the original home by more than 4m.
- The extensions roof & ridges must not exceed the height of the original house and the eaves must not exceed 2m in height of the boundary of 3m.
- Single-storey extensions must not exceed 4m in height.
- Single storey extension width must not exceed half of the original size of the house.
- Extensions on the side or front of a house must be closer to the property than a public highway.
This legislation covers houses across England that are not restricted by Article 4 directions.
What is the maximum extension without planning permission on homes in conservation areas?
Depending on the outcome of the Neighbour Consultation Scheme, single-storey extension builds in conservation areas are covered by permitted development rights as long as:
- Attached property extensions do not extend beyond the rear wall of the original home by more than 3m.
- Detached property extensions do not extend beyond the rear wall of the original home by more than 4m.
The Neighbour Consultation Scheme
As of 1st June 2019, relaxed planning permissions have been made permanent in England only. This means that single-storey extensions situated outside of designated land and Sites of Specific Interest won’t need planning permission, as long as glazed extensions on attached houses don’t exceed 6m or 8m for detached houses. *Subject to The Neighbour Consultation Scheme
So, there’s never been a better time to invest in an extension for your home!
How big can a building be without planning permission?
The relaxation of permitted developments means that homeowners are now able to add extensions without needing planning permissions. You can add a home extension or conservatory up to six metres, or eight metres if your home is detached, without needing to apply for planning permission. There’s very little standing in the way between you and your dream home!
Prior Approval (Neighbour Consultation Scheme) for Larger Rear Extensions
The Prior Approval / Neighbour Consultation Scheme only applies to larger single-storey rear extensions that go beyond the usual permitted-development depth (i.e., over 3 m for attached houses or over 4 m for detached) up to the larger-limit cap. It generally doesn’t apply on certain types of designated land (e.g., many conservation areas or SSSIs) or where an Article 4 Direction removes PD rights, so it’s worth checking with your Local Planning Authority (LPA) first.
If you’re eligible, you submit a “Prior Approval: Larger Home Extension” application with basic drawings and details. The LPA then notifies adjoining neighbours and runs a consultation (typically 21 days). After considering any comments, the council decides whether the extension’s impact on neighbouring amenity is acceptable and either grants prior approval (or confirms it isn’t required) or refuses it. This isn’t a full planning application—the assessment is narrower—but you still must meet all PD limits and conditions. If approved, keep the decision notice and remember that Building Regulations (and any Party Wall requirements) are separate and still apply.
What are the benefits of a glazed extension or conservatory?
So now you know about the planning permission guidelines, but why extend your home? Here are 5 great reasons to carry on with new conservatory and extension plans this year.
Glazed extensions = more space, more enjoyment
When you desperately need extra space, an extension is an economical solution that takes no time at all to install. From refreshing contemporary kitchen extensions to impressive home offices, right through to made-to-measure glazed extensions. With a style to suit all properties, lean-to conservatories make the ideal accompaniment for homes with limited space, whereas P-Shaped conservatories are perfect for larger homes.
Glazed extensions add privacy
If you’re looking for a way to update an existing glazed extension space, a solid roofing system will blend seamlessly with the existing aesthetics whilst offering more privacy inside. This is an ideal option for homes overlooked by neighbouring properties.
Cheaper than moving to a new house
When you consider the current state of the housing market, it’s hardly surprising that more and more homeowners are choosing to improve rather than move. Ideal for those struggling for space or unable to find a suitable property, once the market recovers, you should experience notable property value increases too.
Glazed extensions light up your life
Imagine relaxing in your new conservatory, orangery or extension space throughout the seasons. Watching the world go by, your worries just melt away in a glorious glazed extension space.
Bathing in warming natural light has many health benefits, including increased production of Vitamin D, which is essential for healthy bones and lowering blood pressure. If your budget permits, a grand gable conservatory will expertly maximise the light entering your home.
For more ideas on how to increase the amount of sunlight in your home, read our top blog about how to cleverly maximise light!!
Make the most of your garden & enjoy nature all year round
If you have a garden or enclosed outdoor area, staying home doesn’t have to mean staying inside. A glazed extension allows you to merge indoor and outdoor areas together, especially if you add sophisticated French doors, streamlined bi-fold doors or maximising sliding patio doors into the mix. Providing the perfect setting to appreciate nature all year round, a glazed extension from SEHBAC is a must for keen bird watchers and stargazers too.
And so long as you follow the guidelines listed above, all this can be yours without the hassle of applying for planning permission!
Quality home extensions in South East England
If you require extra living space as your family grows, our range of bespoke extensions will provide the ideal finishing touch to any South East home. The right levels of experience and quality can truly make or break the quality of your renovation. So, be sure to employ the very best installers around. Get in touch with the award-winning SEH BAC team today for all your home improvement needs.
FAQs extensions without planning permission
Under standard permitted development (PD) for typical householder extensions you don’t have to formally notify neighbours (though it’s courteous to let them know). If you use the “Larger home extension” prior approval route for a single-storey rear extension that exceeds the usual PD depth (beyond 3 m for attached or 4 m for detached), you must apply to your council and they will notify adjoining neighbours and run a consultation (timings vary; many use ~21 days for comments and ~42 days overall). On designated land (e.g., conservation areas or SSSIs) or where an Article 4 Direction removes PD rights, the larger-extension route may not be available—check with your Local Planning Authority. Separately from planning, you may need to serve notice under the Party Wall etc. Act 1996 if your works affect a party/boundary wall or involve excavations near foundations. Official guidance: Planning Portal: Prior approval — Larger home extensions; Extensions — planning permission (householder); Permitted development rights; GOV.UK: Party Wall etc. Act guidance.
Yes. Planning permission and Building Regulations are separate. Even when an extension qualifies under permitted development (PD), the work must meet Building Regulations (e.g., structure, fire safety, insulation, drainage) and typically requires Building Control sign-off or an approved inspector. See: Planning Portal – Extensions and Planning Portal – Building Regulations approval.
Some PD rights still apply, but they are more limited on designated land (including conservation areas, National Parks, AONBs, World Heritage Sites, and the Norfolk/Suffolk Broads). In many cases, side extensions, cladding, or larger single-storey rear extensions may be restricted, and an Article 4 Direction can remove PD entirely. Always check with your Local Planning Authority. See: Planning Portal – Permitted development rights (designated land & Article 4) and Prior approval: Larger home extensions.
The “original house” means the building as it stood on 1 July 1948 (or, if built after that date, as it was first built). Previous extensions are not part of the original house, so depth/volume/percentage limits are measured from the original rear/side walls, not from later additions. See: Planning Portal – Permitted development rights (definition of original house) and Planning Portal – Extensions (householder rules).
Side extensions can be PD if they are single-storey, modest in size/height, and not wider than half the width of the original house; two-storey side extensions usually need permission. Front extensions are generally not PD if they project beyond the principal elevation that fronts a highway. Local limits and Article 4 Directions may further restrict this. See: Planning Portal – Extensions (front/side rules) and Permitted development rights overview.
Related articles
- Conservatory Planning Permission
- Do I need planning permission for a conservatory?
- What is the maximum you can extend your house?
Further Reading: UK Planning Portal
The measurements and rules on this page are based on the UK Planning Portal’s official guidance for householder extensions and permitted development rights in England. We’ve condensed the essentials below and linked to the relevant Portal pages for verification.
England only. Local Article 4 Directions or designated land status may restrict PD rights; always confirm with your Local Planning Authority.
Information checked against: UK Planning Portal – Extensions, Prior Approval (Larger Home Extensions), Permitted Development Rights.
Last reviewed: 1 October 2025
