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Single storey rear extension: the ultimate guide for UK homeowners

5 min read
Oct '25 • by Heather

Quick summary

A single storey rear extension in the UK can typically go up to 3m for terraced or semi-detached homes and 4m for detached properties under permitted development rights, without planning permission, if it meets specific rules. Larger extensions usually need full planning permission and can take around 9 to 12 months and cost about £1,500 to £2,500 per sqm, VAT included.

Adding a single storey rear extension presents a great alternative to moving house while adding value and personal style to your home.

They’re perfect for growing families looking to add more space and can be made to fit whatever preferences you may have.

If you’ve been thinking of adding a single storey rear extension to your home, you’re in for a treat. This blog post covers everything about adding a single storey rear extension. From the size to building regulations, planning permission to construction times, you'll find everything you need broken down here.

What is a single storey rear extension?

Single storey rear extensions are extensions with one storey that are added to the back of your home.

They’re a fantastic way to add some extra space while maximising the space you have. Plus, like with most extensions, you could design them to fit your family's needs, be it a study, a kitchen, an extra bathroom, or a spare bedroom.

Ready to start your project? Get your free Resi quote here.

Rear extension ideas to inspire your project

A ground floor rear extension in Barnet

A single storey rear extension in Barnet, completed in 2021

This ground floor rear extension was constructed with matching brick material so that it fit right into the Barnet crowd while serving as an excellent space for recreation and entertaining guests.

A single storey rear extension in Barnet, completed in 2021

How much does an architect charge?