Before applying for planning permission, you should familiarise yourself with the extensions and alterations to dwellings supplementary planning document (PDF 1.1Mb). This provides householder applicants with a clear indication of what we'll consider acceptable when applying for planning permission.
If you still require further advice please be advised that you will need to submit a pre-application enquiry.
This should at the least include existing/proposed floor plans and elevations so we can make a meaningful assessment. As a guide we aim to deal with pre application enquiries within 8 weeks.