Permitted development

How big can your extension be — without planning permission?

Many homeowners assume they need planning permission to extend their home — but that’s not always the case.

Under permitted development rights, you can often build certain extensions without applying for planning permission, as long as they meet specific criteria.

Some general rules (in most areas — always check locally):

Single-storey rear extensions:

• The extension must not cover more than 50% of your garden.

• Typically up to 3–4m deep, depending on the property type.

• Height restrictions apply:

  • Eaves must not exceed 3m high.

  • Overall height must not exceed 4m.

    
    

• Side extensions can also fall under permitted development but only in very specific circumstances.

• No more than 4m in height.

• If within 2m of the boundary the eaves cannot exceed the height of the existing eaves or 3m, which ever is lower.

• the extension can not be wider than half the width of the existing house

• It can not face onto a road.

• The extension can not be forward of the principal elevation or a side elevation that fronts a road.

But there are exceptions:

• If your property is listed or in a conservation area, the rules are stricter or permitted development may not apply.

• Flats and maisonettes don’t usually have permitted development rights.

  
  

If you’re unsure, speak to a professional — we can help you confirm what’s possible before you invest time and money.