Green Belt Planning Rules for Extensions and Outbuildings (2024 Guide)

Green belts are designated areas of land which local planning authorities aim to keep permanently open. If you own a property in a green belt and you’re thinking about applying for planning permission to extend or build an outbuilding, there are a few things you should know first.

Is your property in a green belt?

The first step is finding out if your property is in a green belt. A quick call or email to your local planning authority should get you the answer. Alternatively, many authorities make this information easily accessible on their websites, often providing an interactive map where you can check the green belt boundaries.

So, how does the green belt affect planning applications?

The National Planning Policy Framework (NPPF) is a key Government publication that local planning authorities must follow when assessing planning applications. One of the rules in the NPPF is that any extension in the green belt must not be a ‘disproportionate addition’ to the ‘original building.’ This rule also normally applies to outbuildings that are closely related to the main house.

What counts as a ‘disproportionate addition’?

This is where things can get a bit subjective. The NPPF doesn’t provide a definition of what a ‘disproportionate addition’ is, leaving it up to each local planning authority to set its own guidelines. Generally, they base their decisions on the floorspace or volume of the extension or outbuilding compared to the floorspace or volume of the original building. For example, a local authority might allow a maximum increase of 30% in floorspace and will normally refuse anything above that. If you need help determining what guidelines your local planning authority applies, get in touch.

Are previous extensions and outbuildings relevant?

According to the NPPF, the ‘original building’ is defined as the building as it stood on 1st July 1948, or, if it was built later, its original construction date. This means that when you submit a planning application, your local planning authority will take into account not only your new proposal but also any previous extensions or outbuildings added since that date.

What if your proposal is deemed disproportionate?

If your local planning authority decides that your proposed extension or outbuilding would be a ‘disproportionate addition,’ it’s not necessarily the end of the road. There are sometimes ways to work around this. For example, you might find that your proposal falls within your permitted development rights, which allow you to undertake certain works without needing planning permission from your local authority.

Alternatively, you might be able to argue that you could undertake a slightly different but similarly sized development under your permitted development rights, and consequently that your local planning authority’s objections to your proposal are unjustified.

The list doesn’t end there. There are various strategies available depending on your specific project, and getting expert advice can help you navigate the system successfully.

Need help? Get a free consultation

Navigating green belt restrictions can be tricky, but you don’t have to do it alone. Whether you're unsure about your property’s green belt status, or need advice on how to approach a planning application, we can help. Contact us for a free consultation tailored to your needs, and we’ll get your project moving in the right direction!

The information contained in this article may have become out of date since it was written. Under no circumstances shall the information contained in this article be taken as professional advice.