Height Limits

You will need to apply for planning permission before building an extension to your house if:

• the extension is higher than the highest part of the roof of the "original house"; or
  
• any part of the extension is more than 4 metres high and is within 2 metres of the boundary of your property. (Loft conversions and dormers have separate rules, explained later.)
  

You should measure the height of buildings from the ground level immediately next to it. If the ground is uneven, you should measure from the highest part of the surface, unless you are calculating volume.