The multi-family guide sets minimum private units of 8-12 m² for one person, 12-16 m² for a couple and 20-30 m² for a family with children, with 25-35 m² comfortable for a family with a small hearth of its own. Divide the unit area by the number of people to check it: a 20 m² unit gives 4 m² each to five people but drops below the 3.5 m² per person that the Sphere humanitarian standard sets as a covered-space minimum once six people live in it.
Part of Multi-Family Housing Design
Minimum private unit sizes are the smallest floor areas at which a household can sleep, store its belongings and keep a door of its own.
The Per-Person Check Catches The Crowded Unit
Every family needs a private space where it can close a door and control its own environment. The guide’s minimums are 8-12 m² for an individual (sleeping and personal storage), 12-16 m² for a couple (adding some private living space) and 20-30 m² for a family with children (parents’ sleeping area, children’s sleeping area, storage). Anything larger improves comfort and reduces friction, and a family unit of 25-35 m² with its own small hearth or stove is comfortable long-term.
An area per household can hide overcrowding, so convert to area per person.
Worked Example: Area Per Person
Inputs: unit areas above; household size; the layout guide’s 3.75-5 people per unit (30-40 units for 150 people).
- Individual: 8 ÷ 1 = 8 to 12 ÷ 1 = 12 m² per person.
- Couple: 12 ÷ 2 = 6 to 16 ÷ 2 = 8 m² per person.
- Family of five in 20-30 m²: 20 ÷ 5 = 4.0 to 30 ÷ 5 = 6.0 m² per person.
- Family of six in 20 m²: 20 ÷ 6 ≈ 3.3 m² per person.
- Largest household that 20 m² supports at 3.5 m² each: 20 ÷ 3.5 ≈ 5.7, so five people.
- Layout-guide average household: 20 ÷ 5 = 4.0 to 30 ÷ 3.75 = 8.0 m² per person.
The 3.5 m² is the Sphere Handbook’s minimum covered living area per person for humanitarian shelter. It is not stated elsewhere in this corpus, so confirm it against the current Sphere edition before relying on it. It is a floor for a short stay, not a standard for a permanent home.
What You Need
- A household census with ages
- A tape or marked rod to check built areas (Measuring Rod)
- Space for a stove where the unit has its own
Method
Step 1: Count the people per unit, not only the families.
Step 2: Pick the area from the guide’s ranges, rising to the upper end for larger households.
Step 3: Divide by people and compare with about 3.5 m² as the lowest figure; aim well above it for long-term housing.
Step 4: Reserve a door and window in every unit, including each sleeping space.
Common Mistakes
- Sizing by family, not people — a grandparent or a lodger changes the sum.
- Counting unusable floor such as hearth and clearance zones as living area.
- Putting a stove in a unit too small to clear it — the stove needs 40 cm from combustible walls (Fire Prevention in Settlements).
Safety
Small rooms and stoves
The smaller the room, the faster carbon monoxide builds up and the less margin there is around a hot stove. Vent every stove to the outside and keep sleeping people away from an unvented fire (Indoor Use and Ventilation).
What’s Next
- Learn next: Shared Kitchen and Dining — what the small unit can leave out
- Combine with: Sound Isolation Between Units — keeping a small unit private