Frequently asked questions

Our guide for a two-storey rear extension is £2,000–£2,700 per m² of new floor space including VAT in the West Midlands, so about £56,000–£75,500 for a 4 m × 3.5 m footprint on two floors (28 m² of new floor space). London is around 20% higher and the North East around 10% lower. Design and approval fees are extra.

It depends on where you live and where the extension goes. In England a two-storey rear extension can be permitted development if it is no more than 3 m deep and at least 7 m from the rear boundary; side, wraparound and front two-storey extensions need planning permission. Wales, Scotland and Northern Ireland have their own rules.

Usually per square metre, yes. The foundations and roof, two of the most expensive parts, are shared between two floors, so each extra square metre upstairs costs less than the first one downstairs. The total bill is higher because you are building more.

Allow 4 to 8 weeks for survey and design, around 8 weeks for a planning decision in England or Wales, and 14 to 20 weeks to build. From first visit to completion, allow around 9 to 12 months for a typical project.

Most people do. We build the new structure first and break through into the house as late as possible, so the disruption inside is concentrated into a few weeks.

No. We can handle the whole project, from measured survey, design and planning to structural design, building control and the build, or just the drawings and approvals if you have your own builder.

Across England, Wales, Scotland and Northern Ireland. The first site visit is free on the mainland; island and remote addresses are by arrangement.

No. The photographs are computer-generated to show typical designs. We will only publish real project photos and real customer reviews.

In England and Northern Ireland, a rear extension of more than one storey is only permitted development if it stays at least 7 m from the boundary opposite the rear wall. In Wales the figure is 10.5 m for the upper floor.

Not in England or Northern Ireland. In England, permitted development side extensions must be single storey; in Northern Ireland they can't be more than 4 m high or wider than half the house, which rules out two storeys. In Wales it can be permitted development if it is 10.5 m from the side boundary, set back 1 m and within the width limit.

Yes for almost every two-storey extension. Foundations must carry two floors and a roof, and openings into the house need steel beams. The engineer's calculations go to building control.

In England and Wales, the Party Wall etc. Act 1996 may require formal notices for work on or near a shared wall or boundary. Elsewhere, talking to neighbours early is still the best way to avoid problems.

In England, new first-floor habitable rooms generally need an escape window or a protected route to an exit. If the work creates a storey above 4.5 m, a protected stairway or alternative is needed.

Yes. We can provide drawings, planning applications, structural design and building regulations approval on their own.

The design stage is priced and invoiced separately. Payment terms for the build, including any deposit, are set out in your written quote and contract before any work starts.

Two Storey Extensions is a trading name of S&K Property Investments and Improvement Ltd (company number 16932889), which contracts with you and invoices the work.