Some house extensions and renovations can be made to houses without planning permission. This is known as Permitted Development.
For an extension to an existing home to be classed as ‘Permitted Development’ there are a few stipulations:
The maximum footprint of the extension or garden room must be less than half of the land around the house as it stood in 1948. This is with a maximum height of the extension of 4m – this reduces to 3m if the extension reaches within 2m of your boundary.
The maximum length of a rear single-height extension is 3m from the back of the house for attached properties if the residence is detached this is then 4m. If the extension is two storeys the maximum length is 3m.
Side extensions cannot exceed more than half the width of the existing house. Roof extensions cannot add more than 40 cubic metres of space to a terraced house or 50 cubic metres to a detached or semi-detached house.
Basements are usually permitted if the work is converting an existing cellar or basement. As long as it is not going to be used for self-contained accommodations. Or that doesn’t change the exterior appearance of the building.
Garden Rooms are also usually ok and permitted depending on size and location. This is as long as you are not creating a self-contained accommodation.
Permitted Development only applies to houses, not flats or maisonettes. Some properties in areas with conservation orders will have different rules.
If planning permission is needed it is useful to get pre-application advice from your local council. These helps to highlight any potential issues with your application.