Class Q is a permitted development right that allows agricultural buildings — barns, cowsheds, and similar structures — to be converted into homes without a full planning application, subject to a Prior Approval process.
The rules changed significantly in 2024
Class Q was substantially amended in May 2024, and the transitional period for applications under the old rules closed in May 2025 — so the current rules below are now the only ones that apply.
What's now allowed:
- Up to 10 dwellings on a single agricultural unit (previously 5)
- A combined maximum floor area of 1,000 sqm across the whole scheme
- Each individual dwelling capped at 150 sqm (previously up to 465 sqm was allowed for a single large dwelling — that's no longer possible)
- A single-storey rear extension of up to 4 metres is allowed, but only on hardstanding that already existed on or before 24 July 2023
A genuinely useful widening: the building no longer has to have been used solely for agricultural purposes. It just needs to be part of an established agricultural unit as of 24 July 2023 — opening the door to former equestrian or mixed-use buildings that wouldn't previously have qualified.
Where Class Q doesn't apply
- Land within National Parks, National Landscapes (AONBs), Conservation Areas, or World Heritage Sites
- Listed buildings, curtilage-listed buildings, scheduled monuments, or land within a Site of Special Scientific Interest (SSSI)
- Sites within a safety hazard area or military explosives area
- Where a new agricultural building was put up under separate permitted development rights within the last 10 years
- Where the resulting dwellings wouldn't meet the government's Nationally Described Space Standards
It's conversion, not rebuilding
Class Q covers genuine conversion — replacing windows and roofs, installing services, and similar work reasonably necessary to make the building habitable. It does not cover demolition and rebuilding, or major structural replacement. A structural engineer typically needs to confirm the existing building is genuinely capable of conversion without new primary structural elements before an application will succeed.
You still need Prior Approval
Class Q is not automatic. You must submit a Prior Approval application, and the council assesses it against a defined set of criteria (things like transport access, noise, and design). It can be refused.
Worth knowing: Class R
If residential conversion isn't right for your buildings, Class R offers a similar route for converting agricultural buildings into commercial or office space instead — also expanded in the 2024 changes, with the allowable floor space increased from 500 sqm to 1,000 sqm.
Given how much detail and nuance sits behind these rules, it's genuinely worth getting advice from a planning consultant before committing to a Class Q scheme, particularly on anything with more than one or two dwellings.