Planning in the UK is a complicated process and filled with pitfalls for the unwary.
If you would like an extension to your home or a new-build house then you will require planning permission.
However if you require extra space in the form of a building in your garden then generally you should not require any planning permission if the proposed building fits a number of specific criteria.
The guiudelines are that the proposed new building must be:
and must not be
(Further details can be found on the office of the Deputy Prime Minister web site.)
This is known as permitted development, although for those living in an AONB, conservation area or national park unfortunately the rules are different. However for the majority of homeowners, the law allows for some creative and beautiful buildings that add extra living space and will increase the overall value of your house.