Converting a redundant dairy under Class R

Class R of Part 3 of Schedule 2 to the General Permitted Development Order 2015 allows an agricultural building and the land within its curtilage to change to a flexible commercial use without a planning application, subject to a cumulative floorspace cap of 500 m². For a redundant dairy that is often the fastest route to a letting. Class R flexible commercial use covers storage and distribution, hotel use, and the broad Class E commercial, business and service category, which takes in offices, light industrial processes, indoor sport, clinics, nurseries and shops.

What Class R does not do is permit any building work. It is a use right. Cutting a new opening, inserting a mezzanine, replacing the cladding or adding a loading bay all need their own permission, and an applicant who starts work on the strength of a Class R notification is exposed.

What Class R permits and what it excludes

The building must have been used solely for an agricultural use as part of an established agricultural unit. There is a date qualification, so a building brought into agricultural use recently does not qualify, and a building that has had a mixed or non-agricultural use will not either. Check the history before anything else, because the evidence question is where these schemes fail.

Class R is not available where the building is listed or is a scheduled monument, and an Article 4 direction can remove the right for a defined area. The cumulative 500 m² cap applies across the whole established agricultural unit, not per building, so earlier Class R changes on the same holding eat into the allowance. That catches farms that converted a small barn five years ago and have forgotten it.

The floorspace limit and how it is measured

The cap is cumulative floorspace changing use, which means internal floor area of the parts taking the new use. A dairy with a 320 m² milking parlour and a 240 m² collecting yard under cover cannot convert the whole of both, and the applicant has to choose which parts go and which stay in agricultural use. Draw the split on a plan and keep it, because the boundary between the two uses becomes a boundary for planning purposes.

Mezzanines are the usual dispute. Adding a floor to gain lettable area is building work outside Class R, and it also adds floorspace against the cap. Where the building already has a first floor in agricultural use, that area counts.

Prior approval: two regimes in one class

Below and above 150 m² the procedure differs, and the difference is not cosmetic.

Where the cumulative floorspace changing use is 150 m² or less, the developer notifies the local planning authority. There is no approval to obtain, only a notification to give. Keep the acknowledgement, because in ten years it is the only evidence the change was lawful.

Above 150 m², an application for prior approval is required and the authority may consider four matters: transport and highways impacts, noise impacts, contamination risks, and flooding risks. Nothing else. Design, appearance, landscape impact, residential amenity beyond noise, and the loss of agricultural land are all outside the scope, and an authority that refuses on those grounds is refusing on a matter it cannot consider.

That narrow scope shapes what to submit. Address the four matters directly and briefly, and resist the temptation to submit a full design narrative that invites comment on matters the authority cannot weigh.

• Transport and highways: existing access geometry, visibility splays, trip generation for the proposed use, parking and turning within the site. A short Transport Statement is usually proportionate.
• Noise: plant, deliveries and hours, assessed against the nearest noise-sensitive receptor rather than in the abstract.
• Contamination: the agricultural history matters here. Fuel tanks, sheep dip, asbestos cement roofs and pesticide stores are the usual finds, and a desk study feeding a contaminated land assessment is the proportionate response.
• Flooding: the flood zone, and whether the proposed use is more vulnerable than agricultural storage.

Reverting to agricultural use afterwards

Flexible use is the point of the class. A building that has taken a Class R use can move between the permitted uses and can revert to agricultural use, which is unusual and valuable. It means a farm can let a building commercially for a period and take it back into the holding without a further application.

Two cautions. Once the building has been in a Class E use, the shape of any future permitted development rights for agricultural buildings changes, because Part 6 rights attach to agricultural units and agricultural use. And the Class Q route to a dwellinghouse has its own qualifying conditions, so a Class R change may affect a later residential ambition. Where a dwelling is the eventual aim, take advice on the sequence before notifying.

Building Regulations, fire and the things Class R ignores

A change of use is a material change of use under the Building Regulations, which means the building has to be brought up to standard for the new use even though no planning permission is needed. Agricultural buildings are exempt from most of the Regulations; that exemption goes the moment the use changes.

In a former dairy the recurring items are structural adequacy of an uninsulated portal frame, fire separation between units and means of escape, thermal upgrading for Class E occupation, drainage and sanitary provision, and asbestos in cement sheet roofing and rainwater goods. Budget for them. A conversion priced on the Class R notification and not on the Building Regulations work is a conversion that stalls.

Access and servicing sit awkwardly across the two regimes. Highways is a prior approval matter above 150 m², but the practical work of widening a farm access or forming a turning head is engineering work that needs its own permission. Deal with the access permission and the Class R notification together rather than sequentially.

When a full application is the better route

Class R is the wrong tool in four situations. Where the scheme needs more than 500 m². Where substantial external alterations are integral to the letting, because you will need permission anyway and a single full application is simpler than a notification plus an operational development application. Where the building is listed. And where the intended use falls outside the available classes, which includes most hot food takeaways, drinking establishments and other sui generis uses.

A full application also lets you argue the merits, which matters where the site is in a National Landscape or the Green Belt and the authority's concerns are about landscape and openness. Those concerns cannot be weighed under Class R, so an authority which holds them will look for reasons within the four matters instead. The broader options for a holding are set out in the note on farm diversification into workshops and offices, and the supporting case for a full application belongs in a Planning Statement.

Illustrative example. A 480 m² former dairy is split into three units of 160 m² each for Class E light industrial use. Cumulative floorspace exceeds 150 m², so prior approval is sought. Transport, noise, contamination and flooding are addressed in four short sections. Separate applications cover the new pedestrian doors, the roof lights and the widened access. Figures are illustrative.

This is general guidance, not legal advice. A Lawful Development Certificate is the only formal way to confirm that works or a use are lawful. Check the position with your local planning authority or a qualified professional before relying on it. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.