Two-storey extensions offer the best value per square metre of any extension type — you gain twice the space for less than twice the price. Here is what a two-storey extension actually costs across Redditch, Birmingham, Solihull and Warwickshire in 2026.
Typical cost ranges
- Modest two-storey side/rear extension, standard finish: £90,000–£140,000
- Mid-range two-storey extension with good glazing: £140,000–£220,000
- High-spec two-storey with structural glazing, premium fit-out: £220,000–£350,000+
On a per-m² basis, expect £1,900–£2,600 for standard finish and £2,600–£3,400 for higher-spec builds. That’s slightly higher than single-storey per m² because of the added structural complexity, but because you get double the floor area for one shared roof and foundation set, the total cost per m² of usable space is often less.
What you typically get
A typical mid-sized two-storey rear extension in the West Midlands gives you:
- Downstairs: Extended kitchen, family/dining area, or a new utility and cloakroom
- Upstairs: An additional bedroom (often the master), plus a new en-suite bathroom
Cost drivers unique to two-storey builds
Structural design
Removing an existing external wall at ground floor level to open into the extension requires more substantial steels and calculations than a single-storey equivalent.
Scaffolding
A full scaffold across two storeys adds significant cost versus a single-storey where a mobile tower is sometimes enough.
Rooflines
Matching the new roof back into the existing (either as a continuation, a gable, or a hip roof) needs careful design and typically more labour on site.
Planning considerations
Two-storey extensions to the rear can fall under Permitted Development but only up to 3m out from the original rear wall, and only with restrictions on side-facing windows. Anything larger normally needs full planning permission. Side two-storey extensions almost always need planning permission because they change the front elevation.
Timeline
A typical two-storey extension in the West Midlands runs 16–22 weeks on site. Add 8–16 weeks before for planning and prep. Weather-proofing the shell early is important so first fix trades can work internally in winter months.
Serving homeowners across West Midlands, Worcester, Birmingham, Solihull, Gloucester and the wider region.