"Is this flat too small?" has an official answer. The nationally described space standard (NDSS) sets minimum gross internal areas for new dwellings — from a 37 m² studio to a 138 m² six-bed house — plus minimum bedroom sizes, widths and ceiling heights. This checker looks any combination up instantly.
Check minimum dwelling sizes
The checker needs JavaScript. The full table is in the official standard.
The rules beyond the headline area
- Bedrooms: singles at least 7.5 m² and 2.15 m wide; doubles at least 11.5 m², with the main double at least 2.75 m wide (others 2.55 m).
- Ceiling height: at least 2.3 m over 75% of the gross internal area.
- Storage: built-in storage on top of the GIA — from 1.0 m² for one-bed homes rising to 4.0 m² for six-bed homes.
- Studios: the 39 m² one-person minimum drops to 37 m² where the home has a shower room instead of a bathroom.
Does the standard apply to your scheme?
The NDSS only bites where your local planning authority has adopted it through a local plan policy — but most urban authorities now have, London applies it through the London Plan, and even where it is not formally adopted, officers use it as the benchmark for "acceptable living conditions". Conversions and permitted-development flats are where undersized units most often get challenged — natural light is the other half of that argument, which is where a daylight assessment comes in.
How Fortress Associates can help
Space and light travel together in planning committee reports. If your unit sizes are tight, evidencing good daylight to BR 209 (2022) and BS EN 17037 materially strengthens the case — see our daylight targets tables, run the daylight calculator, or commission a full report (4–5 days, no advance payment). All our free tools live at /free-tools; questions to the team.
Sources & further reading
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