What size extension can I build without planning permission?

In the UK, the rules and regulations surrounding building extensions can be complex and daunting for homeowners. Many people wonder whether they need planning permission to build an extension, and if so, what size of extension is allowed. Fortunately, there are some general guidelines that can help clarify the situation.

Firstly, it is important to note that the rules and regulations around building extensions vary depending on the location of your property. Different areas may have different planning restrictions in place, so it is always best to check with your local planning authority before starting any work.

In general, if you are planning an extension to a detached property, you may not need planning permission if it meets certain criteria. The extension must not exceed more than 50% of the total land area of the original property, and it must not exceed 4 metres in height. The extension must also not be located forward of the principal elevation of the original house that fronts a highway.

For semi-detached and terraced properties, the rules are slightly different. In these cases, the extension must not exceed 3 metres in height, and it must not extend more than 6 metres from the original rear wall of the property for a single-storey extension, or 3 metres for a double-storey extension.

In some cases, you may still need to apply for planning permission even if your proposed extension falls within these guidelines. This could be because your property is located in a conservation area, or because it is a listed building. In these cases, it is particularly important to seek advice from your local planning authority before starting any work.

It is worth noting that building regulations approval will always be required for any extension work, regardless of whether planning permission is needed. Building regulations ensure that the construction work meets certain safety, energy efficiency, and structural standards.

How big can a building be without planning permission?

In general, the size of a building that can be constructed without the need for planning permission will depend on a number of factors, including the type of building, its location, and the purpose for which it will be used.

For example, in addition to the guidelines mentioned earlier for building extensions, there are certain size limits that apply to other types of building work. These include:

• Outbuildings: You can construct a detached outbuilding, such as a garden shed or greenhouse, without planning permission if it is not more than 2.5 metres in height and does not cover more than half of the garden area.
• Garages: You can construct a garage without planning permission if it is not more than 4 metres in height (or 2.5 metres if it is within 2 metres of a boundary) and does not cover more than half of the garden area.
• Porches: You can construct a porch without planning permission if it is not more than 3 metres in height and does not cover more than 3 square metres in floor area.

It is important to note that these are general guidelines, and there may be additional restrictions or requirements depending on the specific circumstances of your building project. For example, if your property is located in a conservation area, there may be additional planning restrictions in place.

Additionally, it is worth noting that even if your building project does not require planning permission, you will still need to comply with building regulations. Building regulations set out minimum standards for things like structural stability, fire safety, and energy efficiency, and ensure that buildings are safe and fit for purpose.

Overall, it is important to carefully consider the rules and regulations surrounding building extensions before starting any work on your property. By following the guidelines and seeking advice from your local planning authority, you can ensure that your extension project proceeds smoothly and legally.