How much does a double storey extension cost? (2026 guide)
A double storey extension adds space on two floors at once, which makes it one of the most efficient ways to enlarge a home. If you need both more living space downstairs and an extra bedroom upstairs, it is well worth understanding the cost. As FMB-registered builders with over 20 years of experience in Solihull and the West Midlands, we build double storey extensions end to end, and this guide explains the price and what drives it.
What is a double storey extension?
A double storey extension, sometimes called a two storey extension, adds new rooms on both the ground and first floors in the same footprint. Most commonly it enlarges the living space downstairs while adding a bedroom, and often an en-suite, upstairs. Because you are building two floors on one set of foundations, you get a lot of extra space for a relatively modest increase over a single storey extension.
How much does a double storey extension cost?
The ranges below give a realistic guide for Solihull and the wider West Midlands. They cover the building work to a good standard, with kitchens and bathroom fittings usually quoted separately.
| Project | Indicative cost |
|---|---|
| Double storey extension | £55,000 to £120,000 |
| Single storey rear extension | £30,000 to £70,000 |
| Typical build rate | £1,800 to £3,000 per m² |
Figures are indicative UK ranges to help you budget and are not a quote. Actual costs depend on size, specification and site conditions.
Is a double storey extension cheaper per square metre than single storey?
In value terms, a double storey extension is often the smarter buy. The two most expensive parts of any extension are the foundations below and the roof above. In a single storey extension, those big fixed costs serve just one floor of new space. In a double storey extension, the same foundations and roof serve two floors, so the cost is spread further and the price per square metre usually drops. That is why, if you need the space on both levels, a double storey extension frequently gives you more for your money. We explain this trade off in more detail in our single storey versus double storey extension comparison.
What gets added on each floor?
Every home is different, but a common layout is an open plan kitchen and dining area on the ground floor, with a double bedroom and en-suite above. Others use the extra ground floor space for a larger living room or a utility and boot room, and the upstairs space for a bigger main bedroom with a dressing area. Part of the design stage is working out the layout that adds the most value and comfort for how you actually live.
What affects the cost of a double storey extension?
- Size. A larger footprint means a higher total, though good value per square metre.
- Structural work. Opening the ground floor into an open plan space needs steel beams, and the first floor loads must be carried correctly.
- Roofline. How the new roof ties into the existing roof affects both cost and appearance, and a careful join is worth getting right.
- Bathrooms and kitchens. An en-suite upstairs and a kitchen downstairs add plumbing and fittings to the budget.
- Finish. Glazing, flooring and heating choices move the figure within the range.
Do I need planning permission for a double storey extension?
Double storey extensions are more likely to need full planning permission than single storey ones, because they more often exceed permitted development limits, particularly on height and how far they project. We confirm exactly what your property needs before any work begins, prepare the drawings, and manage building regulations and building control. See our planning permission guide for the detail.
Does a double storey extension add value?
A well built double storey extension is one of the strongest ways to add value to a home, because it increases both the living space and the number of bedrooms, which are the two things buyers value most. Adding a bedroom and en-suite in particular can move a property into a higher price bracket. As with any extension, the value added depends on the quality of the design and build and on how well the new space suits the house, which is why it pays to use an experienced, accredited builder. In the right home, the uplift in value can offset a large part of the cost.
How long does a double storey extension take?
Most double storey extensions take around twelve to twenty weeks on site, depending on size and specification, with the design and any planning application happening beforehand. We give you a clear programme up front and keep you informed at every stage. You can explore our full house extensions service and see finished projects on our case studies page.
Get a free quote
Every project is different, so the most reliable way to get an accurate price is a free, no obligation site visit. As FMB-registered builders based in Solihull, we will talk you through your options and give you a clear, itemised quote.
Call 07393 194 336Get a free quote