Planning consent and building control approvals are valid for 3 years. If you start building before the end of 3 years and the works are inspected by the council you have no time limitations.
Research other similar properties in your area using the council’s web links to establish acceptable designs and get an understanding of any planning issues that need to be resolved. Some council websites are easier to research than others. Where information has been frozen then direct contact with planners will be required.
No planning is needed for single storey rear extensions of 6m for semi-detached or terraced and 8m for detached homes; this from Planning Portal must be submitted to council. This scheme is only valid for 3 years and currently the building works MUST be completed on or before 30th May 2019. The is NO application fee and the process is a very economical process as minimal drawings are required.
PDR’s are permitted development rights given to many houses throughout the UK allowing a variety of extensions without the need for planning consent; there are clear exceptions including if your property is listed, a flat (or maisonette) or the rights have been removed. Dwellings in conservation areas have reduced limited rights and houses in green belt areas are not affected. Check out Planning Portal for extra guidance.