We won’t lie to you, there are quite a few rules when it comes to building an extension. But this doesn’t have to put you off. Like any game, once you know the rules, you’re more likely to score. Winning you that extension you’ve been dreaming of.

First of all, we’ll be talking about the rules that come with permitted development rights. This is the easiest way to add an extension on your home, as you won’t require planning permission.

When talking about the ‘original house’ in this context, it means the house as it was first built, or as it stood on 1st July 1948, if you reside in an older period property.

Now we’ve got that out of the way, let’s start from the ground up. Here are a few areas that you need to consider...

Rules for Single Storey Extension

• No more than half the area of land around the original house can be covered by extensions or other builds. This includes sheds and other outbuildings.

• No extension can be forward of the principal elevation or side elevation fronting a highway. Meaning, if your extension is building out towards a main road, you may require planning permission.

• Materials must be in-keeping with your property’s current appearance, unless you’re building a conservatory.

• If your property is on designated land, you won’t be allowed cladding on the exterior.

• Single storey rear extensions cannot go beyond the rear wall of the original house by more than three metres if an attached house, or by four metres if detached. If you want a bigger extension, you can think about the neighbour consultation scheme.

• Single storey rear extensions cannot exceed a height of four metres.

Rules for Two Storey Extension

• If more than one storey, your extension cannot extend beyond the rear wall of the original house by more than three metres.

• The maximum height of your extension’s eaves, if within 2 metres of a boundary, is 3 metres.

• Eaves and ridge height of extension can’t be higher than the existing house.

• Two-storey extensions have to be a minimum of seven metres away of the rear boundary.

• Roof pitch must match existing house, or be as close as possible.

• No verandas, balconies or raised platforms without planning permission.

• Upper-floor windows that are in a wall or roof slope in a side elevation must be obscure-glazed and mustn’t open unless the parts which can be opened are more than 1.7 metres above the floor of the room in which it is installed.

• On designated land, two storey extensions aren’t covered by permitted development rights.

• The extensions exterior must use materials similar in appearance to those of the existing house.

Rules for Side Extension

• Single storey, side extensions cannot exceed a height of four metres and mustn't have a width of more than half that of the original house.

• On designated land, no side extensions are permitted.

Rules for Rear Extension

• Single storey rear extensions cannot go beyond the rear wall of the original house by more than three metres if an attached house, or by four metres if detached. If you want a bigger extension, you can think about the neighbour consultation scheme.

• Maximum height of a single-storey rear extension is four metres.

The permitted development allowances described here apply to houses, not flats, maisonettes or other buildings. Resi is able to check with your Local Planning Authority to see if permitted development rights can apply to your build as there may be other constraints to consider.

If you’re looking to extend or renovate your home, avoiding breaking the above rules by booking a a free consultation call with our team.