If you're thinking about planning permission, you will also need to consider building regulation standards. As with planning, there are guidelines for what can be done without the need to apply for approval.
At Everest, we have an expert team that manages planning permission for you and we've created a guide for what you can and can't do when building an extension.
The short answer is that you DON'T need planning permission for an extension if you build within your permitted development rights.
Most of the restrictions that don't fall under permitted development are for work to the front of a house, next to a road or near a boundary.
Planning Permission rules and Building Regulations outlined here apply to houses (not flats/maisonettes), in England. There may be differences in Wales and Scotland.
If you apply through the Prior Approval process you can potentially extend to 6m for a semi or terraced house and 8m for a detached dwelling.
This involves a neighbour consultation scheme and you have to inform your local planning office.
Note, the extended rules do not apply on certain protected/designated land.
Conservatories, orangeries and bay windows are all treated as extensions for planning permission purposes:
Do I need planning permission for a conservatory?
Do I need planning permission for an Orangery?
Do I need planning permission for a bay window?
When extending a house, the building work has to meet specific standards, known as building regulations. The main purpose of the regulations are there for safety purposes and to protect people from potentially dangerous building structures and bad workmanship.
Building regulations is a separate process from planning permission and where relevant must be applied for separately.
In short, you DO need building regulations approval for certain elements of an extension.
Building an extension can be more complicated than a conservatory, so the building regulations must cover all possible variations, such as:
For more information on building regulations for extensions, we recommend you read these in-depth guidelines here.
Prompted by climate change, additions to building regulations came into effect in June 2022. Read about Building regulations Part O here.
As part of a drive towards reducing emissions, the regulations are intended to reduce overheating in houses by:
Windows and glazed areas will be limited to a maximum size depending on:
In high-risk areas, the use of external shading will be required. Internal blinds and curtains and tree foliage cannot be used for shading.
We recommend reading Part O documentation for full guidelines.
In addition to building regulations, you also need to know about the Party Wall Act 1996. The act is mainly to avoid disputes between neighbours and to help find resolve between two parties.
Under the Act, you're required to give notice to a neighbour in the following situations:
You do need to adhere to the Act separate to planning permission and building regulations. We recommend reading about the Party Wall Act here.
In May 2019, the government made permanent the temporary rules for the size of extension that you can build under permitted rights.
If building a single-storey extension of more than four metres up to eight metres from the back of your house (for a detached house, six metres for semi-detached) you have a duty to inform your neighbour. Known as the neighbour consultation scheme.
Halfway between permitted rights and planning permission, the neighbour consultation scheme is a way to keep control of the bigger developments and avoid neighbour disputes.
Instead of speaking to your neighbour directly, you must contact the local planning office and they consult with your neighbours about your development. If your neighbour objects with a fair reason, the planning office can stop your permitted development.
Note, this is only for large extensions over four metres and you can still build up to four metres without having to go through this process.
If you're thinking of adding roof lights or adding new windows to your extension read about when you need planning permission and building regulations for windows here.
Permitted development guidelines for adding an extension to your house refer to the 'original house'. This means the property as it stood on 1 July 1948 or on the date it was built if after. If an extension has been added to the original house then you have to factor this in to any development you can do under permitted development rights.
A local council has the right to override permitted development rights. Check with your local planning office that there aren't any directives in place before you start planning your build.
A property can have a covenant attached to it by a previous owner as a condition of sale. This can be a restriction of any development of the property or building in the grounds of the property. Your solicitor had a duty to inform you of this when you purchased the property so check with them that there hasn't been any previous covenants placed on your property.
Subject to stricter planning rules a listed building needs listed building consent from your local planning office and the permitted development rights might not apply.
Conservation Areas, National Parks, Areas of Outstanding Natural Beauty and World Heritage Sites. As with listed building properties built in designated areas are subject to tighter control and will need approval from the relevant authority.
Information is correct at time of publication: Updated January 2026.
Planning rules are subject to change. Always seek approval from your local planning authority before starting any building work.
