Class O – Offices to Residential Conversion


Class O has finished and is now possible under Class MA

Offices are by far the most popular permitted development opportunity in the GPDO (General Permitted Development Order). Whilst this requires a prior approval application it has been carried out many times within England. Sadly the same opportunities are not available within Scotland, Wales or Northern Ireland.

Note that from September 1st 2020 offices in England will come under the new Use Class E –  this allows for the free change of any of the uses within it. However Class O is date stamped so you can’t change to an office and take advantage. Until the 31st July 2021 the GPDO will continue to use the older Use Class order references as if nothing had changed.


So what can we convert? 


Class O - offices

Quite simply Class O of the GPDO allows for the conversion of offices to any number of dwellings. These can be houses or flats and can be carried out in any part of England as long as it is not a listed building, safety hazard zone, military explosives storage area (probably a good idea!) or an ancient monument. It can be carried out in conservation areas, national parks and other protected land. The only other locations is where local authorities have applied for and obtained an Article 4 in certain areas preventing this type of conversion. These tend to be based around a few business parks. If in doubt check with your local authority. Finally it must have been an office on or before 29th March 2013. So regretfully you can’t build a new office block and convert that. Nice try!

Importantly there is no maximum size to the office block or the number of dwellings that you convert it to.  If you intend to use any unit as an HMO be aware of the new minimum bedroom sizes for HMOs. Note that from 6th April 2021 you will need to adhere to minimum space standards – this is for any prior approvals that are submitted after this date.

You are also not subject to any affordable housing etc. much to the frustration of local authorities.  However you are liable to CIL unless you can use one of the exemptions, which is normally the 6 in 36 rule, this is assuming it is in operation in your council area. You will need to pay CIL for any additional floor space over 100 square metres if applicable.

As from 1st August 2020 you must supply floor plans as part of the application and it will require the the provision of adequate natural light in all habitable rooms of the properties created under Class O. The GPDO defines a habitable room as any rooms used or intended to be used for sleeping or living which are not solely used for cooking purposes, but does not include bath or toilet facilities, service rooms, corridors, laundry rooms, hallways or utility rooms.

if the building is large, you may decide to only convert one or two floors to residential. There is no obligation to convert the entire building. You could convert other floors later as long as they still comply with Class O.





Any external changes will need to be applied for once you have the prior approval as an ‘externals’ application.  This might include new doors, windows, stairwell blocks etc. For the prior approval your drawings should show the external as it is now – as an office – and not how you plan to alter it.


Are the are other constraints?



The prior approval is assed against the following five criteria only: Flood Risk, Noise, Contamination, Highways and natural light. Noise is to prevent you converting an office block next to say a factory. Apart from that you should be good to go. Just remember the block must have been offices on or before 29th March 2013. You might need to prove that. Please do not try and submit a prior approval if work has already started as this is likely to get refused.

Natural light requirement to all habitable rooms was added for any application submitted after August 1st 2020. This will prevent any internal bedrooms from new schemes.

Class O is unique in as much as it is the only prior approval that allows the created dwellings to keep their permitted development rights. So if you create mews houses you can extend them as you would any other house. This does not apply to flats. You can however use your Class L rights to convert to an HMO as long as you are not in an Article 4 area that prevents HMOs and make internal changes to flats.

You must complete the conversion within three years of applying for it and not just started it. There is no end to this class, but the government has said they will review it every five years.

The prior approval costs £96 to submit and takes 56 days to process. If the 56 days has elapsed then you can send in a letter of default to the local planning authority and start works.

That is about it to Class O – it is a fairly straightforward prior approval application and for that reason it has proved popular.

Feel free to make contact if we can be of assistance.

Check out other permitted development options on our changes of use page.


Application form


Click here to download a form for Class O or submit via the Planning Portal. Note that the Planning Portal will levy a small fee for submission via them as they are a private company now. Emailing it direct to the local authority and paying directly is cheaper, but might take longer to process.





Class O – offices to dwellinghouses

Permitted development
O. Development consisting of a change of use of a building and any land within its curtilage from a use falling within Class B1(a) (offices) of the Schedule to the Use Classes Order, to a use falling within Class C3 (dwellinghouses) of that Schedule.

Development not permitted

O.1 Development is not permitted by Class O if—
(b) the building was not used for a use falling within Class B1(a) (offices) of the Schedule to the Use Classes Order—
(i) on 29th May 2013, or
(ii) in the case of a building which was in use before that date but was not in use on that date, when it was last in use;
(d) the site is, or forms part of, a safety hazard area;
(e) the site is, or forms part of, a military explosives storage area;
(f) the building is a listed building or is within the curtilage of a listed building; or
(g) the site is, or contains, a scheduled monument.


O.2.—(1) Development under Class O is permitted subject to the condition that before beginning the development, the developer must apply to the local planning authority for a determination as to whether the prior approval of the authority will be required as to—
(a) transport and highways impacts of the development,
(b) contamination risks on the site,
(c) flooding risks on the site,
(d) impacts of noise from commercial premises on the intended occupiers of the development, and
(e) the provision of adequate natural light in all habitable rooms of the dwellinghouses,
and the provisions of paragraph W (prior approval) apply in relation to that application.
(2) Development under Class O is permitted subject to the condition that it must be completed within a period of 3 years starting with the prior approval date.

Interpretation of Class O

O.3. For the purposes of Class O, “commercial premises” means any premises normally used for the purpose of any commercial or industrial undertaking which existed on the date of application under paragraph O.2(1), and includes any premises licensed under the Licensing Act 200349 or any other place of public entertainment.

Page Updated:  27th February 2022