Can I change a house after planning permission has been granted?

Once planning permission is granted, the development must be built in substantial compliance with the approved drawings and conditions. Not every change requires a new application - genuinely minor amendments that do not materially affect the character of the development, its impact on neighbours, or its compliance with the local development plan, can sometimes be accommodated informally or through a simple 'non-material amendment' or 'agreement of details' process, depending on the local authority's practice.

However, anything that materially alters the development - such as a significant increase in floor area or height, a change in the roof design that affects neighbouring light or overlooking, a change of use, or moving the structure's position on the site - is not covered by the original grant. In these cases you need to apply either for a new planning permission for the amended proposal, or in some circumstances for permission for retention if the changed works have already been built.

It is often possible, and generally advisable, to apply for permission for the revised design before or during construction rather than building first and regularising afterwards, since retention applications carry higher fees, are subject to public notification and observation in the same way as the original permission, and can be refused - potentially requiring remedial works or removal of the unauthorised element.