In article ,
cantorthomas writes:

The 'quota', I think refers to this, I reckon - if you want to build a
single storey extension in the back garden, you can do so without
planning persmission, so long as it is does not extend the overall
floorspace of the house by more than 10%. Of course this is a one-off
allowance - you can't keep extending by less than 10% every year! I
think there is a cut off date - if the house was extended before the
1930s(?) that extension won't use the quota.

You also need to check the original planning permission for the
house. Two houses were built near be recently, but as they are
rather large for their small plots, they were deemed to have
used up their extra 10% in the original building. I'm told this
is quite common when cramming houses onto plots with little space
around them, as has become common with many new build estates.

--
Andrew Gabriel