The Government has consulted on a significant expansion of Class TA of Part 19 of the GPDO, potentially allowing substantially more Crown development on closed defence sites without a normal planning application.
The proposals include higher floorspace allowances, a new approach to prior approval, development closer to site perimeters, buildings up to 18 metres high and a wider definition of a closed defence site. The consultation closed on 5 August 2026. The existing Class TA rules continue to apply for now.
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What does Class TA currently do?
Class TA of Part 19 was introduced in 2022. It allows the erection, extension or alteration of single living accommodation and non-residential buildings on a closed defence site by or on behalf of the Crown, subject to limitations and conditions.
The Government says each use of the right can save at least 6 to 12 months compared with making a planning application.
More floorspace could be permitted
Class TA currently limits additional single living accommodation to 25% of the relevant floorspace existing immediately before 11 January 2022, while non-residential development is limited to 35%.
The consultation asks whether those limits should rise to 35% or 50% for single living accommodation, and 45% or 50% for non-residential buildings.
The 4,000 square metre cumulative trigger could go
At present, once the cumulative footprint of Class TA buildings erected or extended exceeds 4,000 square metres, later development can trigger prior approval for siting and scale.
Government proposes replacing that cumulative test with an individual-development threshold of 2,000, 2,500 or 3,000 square metres. Only an individual proposal above the chosen threshold would trigger the siting and scale prior approval requirement.
Extensions could move closer to the perimeter
Development is currently excluded within 15 metres of a closed defence site’s perimeter. The consultation proposes allowing extensions and alterations to existing buildings within that zone.
New buildings would remain excluded within 15 metres of the perimeter.
Buildings up to 18 metres high
Where development is more than 25 metres from the site perimeter, new buildings are currently limited to 12 metres in height. Government proposes increasing this to 18 metres.
Extensions and alterations more than 25 metres from the perimeter could also reach up to 18 metres, or the height of the existing building if lower. The 10 metre height restriction within 25 metres of the perimeter would remain.
What counts as a closed defence site could change
A closed defence site currently has to be Crown land, surrounded by a closed perimeter and used exclusively for defence purposes.
Government says the word exclusively has prevented some otherwise operational sites from using Class TA because they contain lodgers or tenants such as other government departments, wildlife organisations, flying clubs or search and rescue organisations.
The proposed replacement is land used wholly or mainly for purposes connected with defence.
A wider definition of non-residential buildings
The Government also proposes clarifying that non-residential buildings can include buildings wholly or mainly used for any purpose connected with defence. Childcare facilities needed to support service personnel are given as an example.
Single living accommodation and dwellinghouses would remain outside that definition.
Existing safeguards would remain
The consultation says no changes are proposed to the existing restrictions relating to protected areas such as National Parks, listed buildings, contamination, flood risk or the 11 January 2022 floorspace baseline.
Nothing has changed yet
These are consultation proposals only. The current Class TA limits and conditions remain in force unless and until the GPDO is amended.
For the wider Crown rights, see our guide to Part 19 of the GPDO.
Read the consultation
You can read the full MHCLG consultation on GOV.UK.
Published: 21st August 2026
