Answer: Not much.
A 'Fallback' position can help though.
The Greenbelt's purpose is set out within the National Planning Policy Framework (NPPF), paras 134, which is to either:
(a) to check the unrestricted sprawl of large built-up areas;
(b) to prevent neighbouring towns merging into one another;
(c) to assist in safeguarding the countryside from encroachment;
(d) to preserve the setting and special character of historic towns; or
(e) to assist in urban regeneration, by encouraging the recycling of derelict and other urban land.
Consequently, there are only a few development typologies that can be built in the Greenbelt. These are also set out within the NPPF para 149-150:
buildings for agriculture and forestry;
some buildings for outdoor sport, outdoor recreation, cemeteries and burial grounds and allotments;
extensions, provided that these do not result in disproportionate additions over and above the size of the original building;
replacement buildings, provided the new building is in the same use and not materially larger than the one it replaces;
limited infilling in villages;
limited affordable housing for local community needs;
redevelopment of previously developed land;
mineral extraction + engineering operations;
transport infrastructure;
re-use of buildings;
(some) material changes in use; and
development proposed by the community.
One of the main tests that schemes proposed within the Greenbelt must be assessed against is 'Openness'. the NPPF says that Greenbelt land should be permanently 'Open'.
Naturally, 'Openness' is a concept that has been debated within planning courts for decades. The courts decided that 'Openness' has both a 'visual' and 'spatial' impacts.
For a recent appeal, my client had built 2x garages of an approved treble garage. The remaining unbuilt garage hung clunkily off the rest of the garage block at an angle. This was initially proposed to appease the council who felt that having a single garage block would preserve 'Openness'. My client eventually thought it would be better to detach the unbuilt garage and move it c.9m south. The council refused the application, citing its 'spatial' impact upon 'Openness'.
Remember however, that 'Openness' as both 'Spatial' and 'Visual' impacts.
My main argument in this appeal, is that the council did not give enough consideration to the scheme's visual impact. The approved scheme represented a 'Fallback' position, which for me, has a greater 'visual' impact upon 'Openness'. Its less visible from the highway and you can still see through the site.
Anyway...you can make your own mind up below:
With regards to the 'spatial' impact, ok...moving the proposed garage c.9m south does spread the built form a bit...but is this 'urban sprawl'? Not really. Come on!
Feel free to read my appeal case.
If you are thinking of designing a scheme in the Greenbelt, please do get in touch.