An extension in Leicester begins with a designation check, because with 24 conservation areas and Article 4 directions over Stoneygate and most of New Walk, the odds of being caught by one are higher here than in the towns around the city.
Inside a conservation area the permitted development limits reduce and a side extension loses its permitted development rights entirely. Where an Article 4 applies, external alterations including windows and doors need permission too, which matters for an extension because the new openings and the ones you disturb in the existing house both fall under it.
The Victorian villa stock in Stoneygate and around it is genuinely good to extend. Deep plots, generous rooms, solid structure and usually side access. The constraint is not space, it is consent, and the design has to start from that rather than run into it at week six.
Out on the interwar, post-war and modern housing at the city edges the picture is ordinary. A single storey rear extension of up to four metres on a detached house or three on a semi can fall within permitted development, with a drive for the skip and side access for the materials.
There is also the larger home extension route on unlisted property: up to eight metres on a detached house or six on any other, by prior approval rather than full permission, with neighbours notified and an answer in about six weeks.
Our extensions work is set out in more detail there, including the stages of a build and how the Building Control inspections fit around them.