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What house extensions require a planning application?

Before embarking on a home extension project, a key question to ask is, do you need to submit a planning application, or would it be covered by "permitted development" rights?

Even a small extension more than likely requires an application if the house is in a designated area, which includes locations like National Parks, the Broads, areas of outstanding natural beauty, conservation areas, or World Heritage Sites. Moreover, any extension within these areas that involves external cladding also needs a planning application. Another factor to consider is, do you live in an area governed by an Article 4 Directive? If so, this restricts or eliminates your right to build an extension without a planning application.

In fact, regardless of your location, if you intend to extend beyond the side elevation of your house, and if that side elevation faces a road, you will need to submit a planning application. Additionally, planning permission is required if your extension would protrude beyond the principal elevation of your house. Determining the principal elevation may not always be straightforward, so seeking professional advice is a good idea.

There are several circumstances where a planning application is always necessary. These include homes that are flats, maisonettes, converted houses, or houses created through certain permitted development rights, either as a change of use or a completely new dwelling.

A planning application is also mandatory if the desired extension conflicts with a specific planning condition. Furthermore, if your extension would cover more than half the area of land surrounding the "original house," even if it wasn't you who constructed any previous extensions, a planning application is required. The "original house" is defined as it was initially built, or as it stood on 1 July 1948 for houses constructed prior to that date.

Listed buildings pose a unique situation, as listed building consent is almost certainly needed to extend such structures. The regulations surrounding listed buildings are typically more stringent to preserve their historical and architectural significance.

When it comes to single-story extensions, specific rules apply. For instance, you cannot extend beyond four meters from the rear wall of the "original house" if it is a detached house, or three meters for other types of houses, without a planning application.

However, if your house is not located in a designated area and meets other requirements, you may be able to extend up to eight meters from the "original house" if it is detached, or six meters for other houses. In such cases, prior approval from your local authority is needed. Prior approval involves a simplified application process compared to full planning applications, with fewer details to submit and fewer reasons for the council to reject the proposal.

If you intend to build a side extension without a planning application, it must not exceed four meters in height, must be single-story, and should not surpass half the width of the "original house." However, if you reside in a designated area, a householder planning application is required for a side extension.

For extensions spanning more than one story, certain limitations must be observed. You should not extend beyond three meters from the rear wall of the "original house" or within seven meters of any opposing "boundary" without a planning application. It is important to clarify that "boundary" refers to the curtilage.

In conclusion, navigating the complexities of planning permission and Permitted Development rights is crucial when considering a home extension. To ensure compliance with regulations and laws it's best to seek professional guidance. If you email, he can give you that guidance.

This post is based on an article Planix's director, Simon Rix, wrote for the market-leading Homebuilding and Renovating Magazine. You can see more of Simon's articles for them here:


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