Guides · 5 min
Do I need planning permission for a side extension?
Side extensions are tighter than rear ones. Here is the plain version.
A single storey is the easier version
A single-storey side extension can be permitted development on a house if it is not wider than half the original house, not taller than 4 metres, and not in front of the main wall that faces the road. It also has to sit within the other national limits.
In a conservation area, or on other special land, side extensions often lose that right and need an application.
Two storeys at the side
A two-storey side extension almost always needs planning permission. Councils look at the gap to the boundary, whether the new part looks smaller than the main house, and the effect on the neighbour.
In Bromley, decisions often talk about keeping about a metre to the side boundary for the full height. Other councils write the test differently.
Check with your council. Rules change, and every house is different.
Questions
Can I fill the gap to the fence?
A single-storey side extension sometimes can. A two-storey one usually cannot, because councils want a gap.
Does a garage at the side count?
If you are extending above or beside a garage, it is often treated as a side extension. Check what is already there.
Check with your council. Rules change, and every house is different.