Guides · 6 min
Green Belt extensions, in plain words
In the Green Belt, the size of the original house often matters more than the style.
The basic idea
National Green Belt rules say an extension is usually acceptable if it is not a disproportionate addition to the original house. Original usually means the house as it was on 1 July 1948, or as first built if it is newer.
What “too big” means in metres is a local question. In our Fawkham sample, Sevenoaks was using a local idea of about 50% over the original floorspace. That number is not a national rule, and it is not a figure to copy to another council.
Do not copy one council’s number
A house that looks modest from the road may already have used its allowance in older extensions. Ask what has been added since the house was built.
Green Belt does not, by itself, remove permitted development rights. A council often removes them later, when it does grant permission.
Check with your council. Rules change, and every house is different.
Questions
Does Green Belt always mean no?
No. Small additions can still be allowed. The hard question is how much the house has already grown.
Is the 50% figure a national rule?
No. It showed up in one council’s sample. Other councils use different tests. Check the rule in force.
Check with your council. Rules change, and every house is different.