Calculate Your Wrap-Around Extension Cost
A wrap-around extension combines a rear extension with a side return extension to form an L-shaped addition.
What Is a Wrap-Around Extension?
A wrap-around extension (also called an L-shaped extension) combines a rear extension with a side return extension. This creates the maximum possible single-storey footprint around the back and side of a property. The result is a dramatically larger ground floor, most commonly used as a large open-plan kitchen-diner-living area.
Wrap-arounds are most popular in London and major cities where terraced and semi-detached Victorian and Edwardian properties predominate. Because the side return and rear extension are built as a single unified project, the cost per m² is often slightly lower than building them separately at different times.
Frequently Asked Questions
How much does a wrap-around extension cost in the UK in 2026?
A wrap-around extension costs £1,800–£3,000 per m² in 2026. Most projects cover 25–50 m², giving a build cost of £45,000–£150,000. Adding a corner structural beam (£5,000–£10,000) and professional fees (12–15%) means total project costs of £55,000–£175,000+ depending on location and specification.
Does a wrap-around extension require planning permission?
Yes, wrap-around extensions almost always require full planning permission because the combined footprint typically exceeds Permitted Development limits for side and rear extensions. In England the planning fee is £206 and the process takes 8–12 weeks. Approval is not guaranteed, particularly in conservation areas or if neighbours object.
What is the corner structural beam cost for a wrap-around extension?
The corner junction where the side return meets the rear extension requires a structural steel frame or corner post assembly. This typically costs £5,000–£10,000 in 2026, including a structural engineer's calculations (£800–£1,500) required for Building Regulations approval. It is a fixed cost premium that applies to all wrap-around projects.
How much value does a wrap-around extension add to a house?
A quality wrap-around extension can add 10–20% to property value in the UK. For a £700,000 London terrace this means a potential uplift of £70,000–£140,000. The large open-plan kitchen-diner-living area created by a wrap-around is among the most commercially valuable features in the current UK property market.
How long does a wrap-around extension take to build?
On site, a wrap-around extension takes 12–20 weeks to complete, longer than a simple rear extension due to the corner junction complexity. Including design, planning permission (8–12 weeks) and Building Regulations approval, the full project timeline from initial appointment with an architect to handover is typically 9–15 months.