1×20 container as an annexe: 14.8 m²
Annex in a 20 ft container. Garden office, guest room or studio for the family: the classic garden annexe. Not an independent home: 14.8 m² built.
The space standard applies only where your council has adopted it in its Local Plan. Check with the council and an architect before you choose a plan.
How much it costs
Between £30,698 and £41,532, VAT included and a ±15% margin. Balanced finish, one-trip containers, residential plot with water, power and drainage. The land is not included.
Container prices from UK depots (2025–2026) and building work with UK factors on the Contentar engine, checked in November 2026. VAT at 20%. Excludes land, heat pump, solar panels, warranty, CIL and stamp duty.
Baseline: one container, window and door openings only.
Build complexity: simple.
For and against
For
- The cheapest and quickest: a single module, no structural cuts beyond the openings.
- Travels whole on a normal lorry and fits tight plots.
- An honest plan: bathroom, kitchenette and living/sleeping with no corridors.
Against
- 14.8 m² built: far below any minimum for a dwelling. It works as an annexe used with the main house (office, guest room), not as a separate home. Confirm with the council.
- In a standard 20 ft the finished ceiling height ends up at ~2.25 m; better a 20 ft High Cube.
Sun orientation
Long south façade with a glazed door and a 60–80 cm overhang; west end almost blank.
Adjust the finish, used or new container and the land, and see the cost line by line.
Work out my cost UK guide · join the waiting listSee this plan in 3D on Contentar
Other plans
- 1×20 container as an annexe: 14.8 m²Annex in a 20 ft container · £30,698–£41,532
- 1×40 container as an annexe: 29.7 m²Studio in a 40 ft container · £42,063–£56,909
- Container home 2×40: 1 bedroom, 59.4 m²1 bedroom · two 40 ft side by side · £78,046–£105,591
- Container home 3×40: 2 bedrooms, 89.2 m²2 bedrooms · three 40 ft side by side · £110,928–£150,078
- Container home 4×40: 3 bedrooms, 118.9 m²3 bedrooms · four 40 ft side by side · £144,913–£196,060
- Container home 2×40 + 1×20 L-shaped: 2 bedrooms, 74.2 m²L-shaped 2 bedrooms with a patio · £92,681–£125,390
- Container home 4×40 H-shaped: 3 bedrooms, 118.9 m²H-shaped 3 bedrooms with two patios · £147,412–£199,440
- Container home 3×40 duplex: 2 bedrooms, 89.2 m²2-bedroom duplex, one 40 on top · £113,847–£154,027
- 1×40 + 1×20 with decking container as an annexe: 44.5 m²40 + 20 ft with decking · £59,228–£80,131
- 2×20 L-shaped container as an annexe: 29.5 m²Two 20 ft in an L · £50,709–£68,607
- 2×40 cantilevered container as an annexe: 59.4 m²Stacked cantilever with a terrace · £85,014–£115,019