An extension in Market Harborough depends heavily on which part of town you are in, and the sharpest dividing line is Little Bowden.
There, the Article 4 direction removes further permitted development rights for front elevation alterations and boundary treatments. For an extension that matters in two ways that are easy to overlook. Anything that changes the front of the building, including a porch, a bay, a new window opening or an alteration to the roofline at the front, is caught. And anything that changes the boundary in front of the property, which frequently includes the temporary or permanent removal of a wall to get plant and materials in, is caught as well.
Neither of those stops a good extension. What they do is push the work to the rear and require the access arrangements to be thought through rather than improvised, and both of those decisions belong at the design stage.
Elsewhere in the town the ordinary rules apply. A single storey rear extension of up to four metres on a detached house or three on a semi can fall within permitted development, and on the estate housing there is usually side access and a drive for the skip. Inside the Market Harborough conservation area the limits reduce and a side extension loses its permitted development rights entirely.
There is also the larger home extension route on unlisted property, up to eight metres or six by prior approval with neighbours notified. Our extensions work is set out in more detail there, including how the Building Control inspections fit around the build.