Planning advice:what permissions do we need to turn a cowshed into a home?

We could have found the perfect barn conversion project within commuting distance, which means it is in the green belt – what planning rules do we need to be aware of?

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Question: ‘We want to move to the country but stay within commuting distance. A family dairy business has offered to sell us its old milking parlour. It looks like the perfect barn conversion project but it is in the green belt — which could make it very contentious. What sort of planning permission will we need?’

Answer: The green belt is in place to safeguard the countryside from sprawl and to encourage the reuse of urban brownfield land, so under normal circumstances new housing in these areas would be considered inappropriate.

However, under permitted development regulations you are allowed to convert an existing agricultural building such as barn or milking parlour with a maximum floor area of 450 square metres to a maximum of three separate dwellings without planning permission.

A number of exclusions apply, including if the building is located within a conservation area, an Area of Outstanding Natural Beauty, a National Park, a Site of Special Scientific Interest, or if the building is listed. Where these do not apply there are still a number of factors you should consider before you take on your project.

Conversion costs are typically more expensive compared to a new build so you should expect to budget between £90 to £150 per square foot, depending on the condition of the building and final specification. Stone constructions are usually the most expensive, followed by wood, with brick being by far the cheapest.

Though your proposal would initially be considered permitted development you’ll still need to make an application for prior approval. The council will assess the impacts of the conversion against a limited set of criteria including transport and highways, contamination and flooding risk. Most of these impacts can be mitigated. However, others are harder to overcome such as the proximity to noisy activities — for example, an intensive poultry farm — or where the building would be near industrial buildings housing dangerous machinery or chemicals.

You will need to make sure that your conversion would provide adequate living conditions, otherwise not only would you fail to satisfy permitted development requirements, but also it will prove difficult to attract potential buyers, if and when you come to sell in the future.

It is important to remember that permitted development rights allow for the conversion of an agricultural building to residential and not its complete redevelopment. Building operations such as the installation of new windows, doors, roofs and exterior walls as well as water, drainage, electricity and gas services are permitted, but structural work is not.

A big reason why “prior approval” applications are refused by councils or dismissed at appeal is that the work required in bringing an agricultural building up to habitable standards goes beyond the alterations permitted. Before you exchange contracts you should consider whether the existing building is structurally strong enough to take the load expected of a residential unit or units, so you should consult a building surveyor about the extent of the works required.

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