Planning Rules
Class Q Permitted Development: Converting Agricultural Buildings to Homes (2025)
Class Q is one of the most significant permitted development rights in England — allowing agricultural buildings to be converted to residential use without full planning permission. Here’s how it works.
⏱ 7 min read📅 Updated June 2025🏠 England only
Quick Answer
Prior Approval required — but planning permission is not
Class Q of Part 3 of the GPDO 2015 permits the change of use of an agricultural building to a dwellinghouse (C3 use class), and associated building operations. The right requires Prior Approval from the local planning authority — the council can only consider specified matters (transport, flooding, contamination, noise, design) and cannot refuse on general planning grounds. Each agricultural unit can produce up to 5 dwellings under Class Q, with a maximum of 3 larger dwellings (over 100m²) and up to 5 smaller dwellings (under 100m²). The building must have been used solely for agricultural purposes as part of an agricultural unit since before 24 July 2017.
What Is Class Q?
Class Q (formerly Class MB) of Part 3 of Schedule 2 to the Town and Country Planning (General Permitted Development) (England) Order 2015 grants permitted development rights to change the use of an agricultural building to a dwellinghouse. It was introduced in 2014 to increase housing supply by enabling conversion of redundant farm buildings.
Class Q has two parts:
- Class Q(a): Change of use from agricultural building to dwellinghouse (C3)
- Class Q(b): Building operations reasonably necessary to convert the building for use as a dwellinghouse
Both Q(a) and Q(b) require Prior Approval. The building operations permitted under Q(b) are limited — they are operations to make the building suitable as a dwelling, not operations to create new building volume beyond the existing footprint.
Key Conditions
| Condition |
Detail |
| Agricultural use |
The building must have been used solely for agricultural use as part of an agricultural unit on or before 20 March 2013, or if it was brought into use after that date, for 10 years before the date of the application |
| Not a new agricultural building |
The building must not have been erected under Part 6 agricultural PD rights within the last 10 years |
| Size limits |
Maximum of 5 dwellings per agricultural unit. No more than 3 dwellings with a floor space of more than 100m² (larger homes). Total floor space of the larger homes cannot exceed 465m² |
| Not listed |
The building must not be a listed building or within the curtilage of a listed building |
| Structural suitability |
The building must be capable of functioning as a dwelling without being substantially reconstructed — the existing structure must be sound |
| Location |
Not on a site of special scientific interest (SSSI), safety hazard zone, or military explosives storage area |
⚠️ “Conversion not reconstruction” is the critical test Class Q only permits works that are reasonably necessary to convert the building — it doesn’t permit wholesale demolition and rebuild. If the existing building structure is so poor that it would need to be substantially rebuilt to function as a house, Class Q doesn’t apply. Courts and inspectors have taken a strict view on this — the building must be structurally capable of conversion as it stands.
The Prior Approval Process
Class Q requires Prior Approval from the local planning authority. You submit an application to the council, which then has 56 days to determine it. The council can only consider:
- Transport and highway impacts
- Noise impacts from surrounding uses
- Contamination risks
- Flooding risks
- Whether the location or siting makes it impractical or undesirable for the building to change use
- Design or external appearance of the building
The council cannot refuse on the basis of general housing policies, visual impact on the countryside, or other matters not listed above. If they fail to determine within 56 days, the Prior Approval is deemed granted.
✅ Deemed approval after 56 days If the council fails to determine a Class Q Prior Approval application within 56 days of acknowledging it as valid, Prior Approval is deemed to be given. This is a powerful backstop — but you should be careful to ensure the application was validly submitted before relying on deemed approval.
What Works Are Permitted
Under Class Q(b), building operations reasonably necessary to convert the building include:
- Installation or replacement of windows, doors, roofs, or exterior walls
- Installation of services (water, electricity, drainage)
- Partial demolition to the extent reasonably necessary for the conversion
Works that go beyond conversion — such as extensions, new structural walls replacing non-existent ones, or creation of new floor space — are not permitted under Class Q and require planning permission.
Frequently Asked Questions
Can I convert a barn to a house under permitted development?
Yes — Class Q of Part 3 of the GPDO 2015 permits the conversion of agricultural buildings (including barns) to dwellinghouses. Prior Approval from the council is required, but the council can only consider specified matters — it cannot refuse on general planning grounds. The building must have been used for agriculture before 20 March 2013 (or for 10 years before the application), must not be listed, and must be structurally capable of conversion without substantial reconstruction.
How many homes can I create under Class Q?
Up to 5 dwellings per agricultural unit under Class Q. No more than 3 can be larger dwellings (over 100m² floor space), and the total floor space of those larger dwellings cannot exceed 465m². The remaining dwellings must have a floor space of no more than 100m² each. The limit applies to the whole agricultural unit — not just the building you’re converting.
What does “reasonably necessary” mean for building works under Class Q?
Building operations under Class Q(b) must be “reasonably necessary” to convert the building for use as a dwellinghouse. This means works needed to make the building habitable — installing windows and doors, replacing a deteriorated roof, adding insulation, connecting services. It doesn’t include extensions, new walls to replace missing structural elements, or creating floor space that didn’t exist before. The test is whether the works are necessary for the conversion, not whether they’re desirable.
Can I use Class Q in a National Park or AONB?
Yes — Class Q applies in National Parks and AONBs (unlike some other PD rights). The council still has Prior Approval jurisdiction and can consider the design and external appearance of the building, which gives them scope to require sympathetic materials and finishes. In sensitive landscape areas, councils often impose detailed conditions on the design. Class Q does not apply in sites of special scientific interest (SSSIs).
More on Permitted Development Rights
Extensions, loft conversions, outbuildings, solar panels — our complete guide covers everything you can build without planning permission.
Read the Complete PD Guide →
