Do I need planning permission? (UK)
If your change-of-use conversion involves only internal alterations, you may not need planning permission; here are some of the projects you can do without planning approval:
Loft conversion – qualifies as permitted development within additional volume limits (40m3 for terraced houses; 50m3 for semi-detached and detached houses), not extending beyond the original roof slope at the front of the house (facing the road) and not extending higher than the existing roof.
Garage conversion – qualifies as permitted development providing the work is internal and the building is not enlarged, although a detached garage may need Change of Use approval.
Convert a space above a shop – if you meet certain requirements, you may be able to convert a space above a shop into a flat without planning permission.
Convert light industrial premises – for applications that are granted prior approval before 1 October 2020 and development is completed within three years of the prior approval date, light industrial buildings can be converted to dwellings, subject to certain conditions.
Barn conversion – agricultural buildings less than 450m2 can be converted to residential use subject to meeting certain criteria.
Some changes of use are subject to a prior approval procedure, which might include matters relating to transport and highways impacts, noise impact, contamination risks, flooding risks, whether the building is suitable for a residential use, and the design or external appearance of the building.
Subdividing a house into a number of flats or bedsits requires planning permission, as do most other changes of use not listed above. Most external work carried out as part of a conversion also requires permission.