Building regulations for extensions — what you need to know to ensure your project sails through the approval process

If you are adding space to your home, you will need to comply with the building regulations for extensions if you don't want to fall foul of the law.

When it comes to building an extension, there are a whole host of aspects to take into consideration, from the materials you'll use to how big you need it to be to meet all of your needs.

However, it doesn't matter whether you plan on building a sprawling contemporary masterpiece or a compact side return extension, there are certain rules and regulations that will always apply.

In this guide, we explain which building regulations you will need to comply with when building an extension and how to navigate the process of getting approval.

What are the building regulations for extensions?

The world of building regulations can be a complex one that can leave homeowners looking to make upgrades or changes to their homes feeling more than a little daunted. So, which of these regulations apply to extensions?

'Building regulations are needed for all building work,' explains architect Darren Bray, director of Studio B.A.D. 'These are legally binding requirements that ensure all construction work meets regulatory standards for safety, energy efficiency and accessibility and is fit for purpose.'

'If you’re planning to extend your home, you will need to comply with the building regulations,' adds Emily Barnes, architect and founder of Design for Me. 'This is a legal requirement and, without formal approval and control, your local council could force you open up or re-build sometimes significant aspects of the project. It could even lead to prosecution and unlimited fines.'

Emily Barnes

Architect Emily Barnes founded Design for Me in order to help residential architects, interior and garden designers find and choose new projects and help homeowners find the right professionals for their project.

Which Approved Documents apply to extensions?

Approved Documents are a set of separate guides for each aspect of a build which lay out how to comply with the building regulations.

Pretty much every aspect of an extension is likely to need to comply with building regs. It is useful to get to grips with which Approved Document relates to which aspect of an extension project. The most common elements are:

• Structural safety: Part A
• Doors and windows: Part N
• Electrics: Part P
• Fire safety: Part B
• Drainage: Part H
• Conservation of fuel and power: Part L
• Overheating: Part O
• Ventilation: Part F
• On-site safety: Part K

What kind of building regulations application do you need for an extension?

The two most common routes to getting building regulations approval for an extension are a building notice (perfect for small extension ideas) or a full plans application – but which will you need?

'This largely depends on the complexity of a scheme,' begins Darren Bray. 'For a larger, more arduous project, we would always suggest you apply for a full planning application, as this route is a more detailed approach. As part of the submission, you include full architectural drawings, specifications and other documentation specific to the scheme. This careful approach ensures everything is pre-approved, reducing any risk of potential issues or costly changes later on in the build.

'A building notice is a simplified route, with only the essential details getting submitted,' continues Darren. 'This can allow for flexibility during the build and can allow you to get started on-site quicker. However, during the construction phase, the building control officers would regularly conduct on-site inspections and recommendations which could involve additional unexpected changes as there are no set detailed plans in place. This route can work well for smaller, less complex projects.'

Darren Bray

Darren set up Studio B.A.D in early 2019, after many years working in a boutique studio, mainly focused on private, high-end residential projects. He set up independently to focus on using architecture to help resolve 21^st century issues, such as environmental, political and economic challenges we all face today. After many years working in private practice Darren has extensive experience working across a vast range of projects, from community schemes to the high end residential dwellings.

Can you build an extension without building regulations approval?

The majority of extensions will require building regulations approval. That said, there are a couple of projects that are exempt, including small additions built at ground levels, such as small front porch ideas or conservatories that are either wholly or partly glazed, and with a floor area less than 30m2.

Other than that though, you will need to comply with building regs.

'It might be possible to build an extension without planning permission, but not without building regulations as these are legal binding requirements in place to ensure the construction work meets regulatory standards and the building and fixtures are fit for purpose,' explains Darren Bray.

'Building regulations apply to almost all types of building work, from a loft conversion to a large rear extension – they all must meet the minimum standards,' continues Darren. 'If you go ahead without these necessary approvals in place, your local council could require you to remove it, or rebuild it to the meet the standards. It would also complicate a future sale of your property.'

What other permissions do you need to build an extension?

Building regs aside, there are also some other permissions you might need to secure before you can build your extension.

'Depending on the scope of the extension you might need to get planning permission before you start work,' advises Darren Bray. 'This applies if the project is a significant addition or alternation, it affects the external appearance or if the property is listed or in a conservation area.

'If you live in a terraced property, or want to build onto a neighbour’s adjoining wall, you will need to get a Party Wall Agreement in place,' continues Darren. 'This ensures that both you and your neighbour are aware of and agree to the work, protecting both parties' interests and addressing any potential disputes.'

The type of house you are extending will also play a role in determining which kinds of approval you will need to organise before starting work.

'When working on a listed building, any alterations require Listed Building Consent from the local planning authority,' explains Darren Bray. 'Listed buildings are protected for their historical and architectural significance, and any changes need to preserve their integrity. Doing work without this consent can lead to serious consequences, including fines or criminal charges.

'If you don’t own the freehold of the property, such as in a leasehold arrangement, you must get Freehold Consent from the freeholder or landlord to clarify everything before proceeding with the extension,' continues Darren. 'Lease agreements can have clauses that restrict modifications, so it’s crucial to carefully review the lease. This consent ensures you are legally allowed to make changes to the property, including building or extending.'

FAQs

Who signs off the work?

Depending on the part of the project in question, it will likely be a Building Control Officer from your local authority (or a Registered Building Control Approver, if you have opted to submit your plans through a private sector building control organisation) who comes to sign off on the work.

However, some tradespeople and installers are qualified to sign off their own work and then report it to the Local Authority under something called The Competent Person Scheme. This includes window and door installers as well as electricians and gas engineers, and can make the process of submitting your approval request simpler.

Using a Competent Person requires you to find someone who is registered with DLUHC (Department for Levelling Up, Housing and Communities)-approved scheme and means that there is no need to apply for building regulations approval for the work they have carried out. They will notify the local authority of the work they have done and also issue you with a certificate of compliance with building regulations.

Unsure whether or not your extension will fall under permitted development? Check out our guide to what size extension can I build without planning permission to find out.