If you’re dreaming of extra space with minimal hassle, it’s crucial to understand what size extension you can build without planning permission. At Simply Extend, London’s leading kitchen extension specialists, we often guide clients through permitted development (PD) rules to maximise space while avoiding unnecessary delays.
Under permitted development rights, homeowners can extend their properties without formal planning approval, provided certain criteria are met:
Rear Extensions Without Planning Permission
For a terraced or semi-detached house, you can extend:
Up to 3 metres beyond the original rear wall.
For a detached house, you can extend:
Up to 4 metres beyond the original rear wall.
These limits apply to single-storey rear extensions under standard PD rights. However, until May 2025, the larger home extension scheme remains in place, allowing:
Up to 6 metres for terraced and semi-detached houses.
Up to 8 metres for detached houses.
This larger extension is subject to Neighbourhood Consultation (prior approval). Your council will notify neighbours to check for objections, but it’s a simpler process than full planning.
Height Restrictions
The maximum height of a single-storey rear extension is:
4 metres overall, or
If within 2 metres of a boundary, maximum eaves height of 3 metres.
For double-storey extensions, planning permission is generally required, as PD allows only limited enlargement. They must not extend more than 3 metres beyond the rear wall and must be at least 7 metres from the rear boundary.
Side Extensions Without Planning Permission
You can build a side extension under PD if:
It is single storey.
Maximum height is 4 metres.
Width is no more than half the width of the original house.
Important Considerations
The original house means as it was built or as it stood on 1 July 1948 (for older properties).
If your property is in a Conservation Area, National Park, or AONB, permitted development rights are more restricted.
Flats and maisonettes do not benefit from PD rights.
Listed buildings require listed building consent for any extensions.
Why Use a Specialist Like Simply Extend?
While PD rules offer flexibility, measuring correctly and ensuring compliance is essential to avoid costly enforcement notices. At Simply Extend, we handle the design, neighbour consultation, building regulations, and construction seamlessly. We ensure your extension maximises allowable space while remaining lawful and beautifully integrated into your home.
Permitted development is a fantastic route to expand your home efficiently. However, laws are subject to change, and local councils interpret them rigorously. For tailored advice on your specific property and to design your dream kitchen extension without delays, speak to our expert team today.
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