How Big Should a New-Build Apartment Be?

Under England's nationally described space standard, a new-build one-bedroom apartment sleeping one person should be at least 39m², or 37m² with a shower room instead of a bathroom. For most new homes the standard is optional. It applies where the local council has adopted it in its local plan, however the homes are built, including modular homes. Since April 2021 it has applied to new homes created under permitted development, such as office-to-flat conversions.

Many developers build larger than the minimum size of 39 square meters (m2), especially in the build-to-rent sector, where homes are sized to what tenants want and need.

Article updated: October 2026

All properties going through development will require sign-off from building control and unless under a general permitted development order, will also require planning permission.

Minimum Gross Internal Floor Areas (m2 )

Here are the sizes the standard sets, by number of bedrooms and residents. The government's planning guidance explains how councils adopt it. Source: Gov.uk nationally described space standard

Apartment Development Notes

1. Built-in storage areas are included within the overall GIAs and include an allowance of 0.5m² for fixed services or equipment such as a hot water cylinder, boiler or heat exchanger.

2. GIAs for one storey dwellings include enough space for one bathroom and one additional WC (or shower room) in dwellings with 5 or more bedspaces. GIAs for two and three storey dwellings include enough space for one bathroom and one additional WC (or shower room). Additional sanitary facilities may be included without increasing the GIA provided that all aspects of the space standard have been met.

3. Where a 1 bedroom, 1 person has a shower room instead of a bathroom, the floor area may be reduced from 39m² to 37m², as shown bracketed.

4. Furnished layouts are not required to demonstrate compliance.

Do Existing Properties Need to Have a Minimum Size Standard?

For existing buildings being converted under permitted development, whether for flipping houses or long-term investment, they also need to fit the same minimum size standards as of April 2021.

There will be apartments that exist throughout the country that were converted before this date that could still fall below these space standards however. For a buyer, a converted flat's floor area is part of due diligence on property, because size affects both the mortgage and which tenants the flat appeals to.

For these properties securing the necessary financing for a buyer to purchase these properties can be challenging and apartments below this size threshold often struggle to qualify for standard mortgage offerings, meaning you'll have to target cash buyers instead.

Why Do New Build Apartments Have Minimum Size Standards?

The standard is there so homes have enough room to live in comfortably. It sets floor areas, room sizes, storage and ceiling height. Energy efficiency is covered by separate modern energy efficiency standards.

The space also leaves room for essential furniture and daily activities. That means a proper bathroom, a kitchen you can cook in and a living area you can use for more than one thing.

Market research consistently shows that there's growing interest in 'efficient' living spaces (although people actually want affordable, not small homes), particularly in urban areas.

Some older developments in cities have flats under 39m². They're a niche, with a smaller pool of buyers.

Outside the flat itself, owners can increase a property's appeal and price, when adding features like a driveway.

The standard's minimum for a one-bedroom home for one person is 39m², or 37m² with a shower room, but local market conditions often demand larger spaces. In areas where existing properties typically offer more generous proportions, strictly adhering to minimum sizes might position new developments at a competitive disadvantage. The key is to align development decisions with local market expectations while meeting the space standard wherever it applies.

If the average apartment size for a one bedroom is 50 square meters in your local area then you are going to struggle to sell and tenant a property at 39m².

For property investors and developers, understanding these size requirements helps inform better investment decisions. Rather than viewing 39m² as a target, it's more useful to consider it as a baseline from which to assess and build a financial model and forecast.

This is helpful when reviewing a new development, considering the land value of the site using the residual method of valuation through to the resale value of the apartments.

Maximising the number of apartments by developing more smaller units isn't always the best solution to increase returns.

Many successful developments opt for slightly larger units - perhaps 45-50m² - where the ability to sell quickly and achieve a higher price per unit is the top focus, rather than an 'on paper' higher margin for the whole development.

This practical approach to size standards, combined with the growing focus on zero-carbon homes, ultimately creates more sustainable developments that maintain their value and marketability over time, benefiting both developers and future property owners.

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