In article ,
"a0000000000" writes:

Relevant for this is Class A which allows the greater of 10% or 50m3 for a
terraced house or greater of 15% or 70m3 otherwise subject to a cap of 115m3
increase in volume of the original dwelling (yes you do count the roof void
too) without planning permission. Surprised if a conservatory is bigger
than this. Conservation areas are different with more rules.

I went along to the planning meeting for two new houses to be built
near me (on what had previously been one plot). Planning permission
was granted, but they were deemed to have used up all their allowed
expansion without planning permission in the initial build. Aparently,
this is normal in cases of tightly packed new housing nowadays. I
presume this would be communicated to the eventual purchasers somehow,
but I don't know how this is done.

--
Andrew Gabriel