We are hoping to build an extension under the required 20 square metres to the back of our house single story big back garden so no planning issues there but was wondering can we extend at the side of the back of the house ( increasing extension beyond exisiting gable wall by 4 feet ) without planning permission! !
you can build at the back up to a certain percentage of the floor area of the house without planning permission, you will need to comply with building regs though. But you better check with your local planning office because as far as i know you cannot extend to the side or front of your house, no matter how big, without planning permission.