This 400 sq ft ADU plan is a single-level detached backyard unit with 410 sq ft of living space, one bedroom and one bathroom. The footprint measures 19'-8" × 23'-0", compact enough for many rear yards. An entry porch leads into the 8'-10" × 11'-7" living room, which anchors the plan. There is no garage and no second level, which keeps the structure simple.
The 7'-8" × 6'-4" kitchenette sits alongside the living room, so cooking and seating share one open zone. A 4'-10" × 3'-7" hall leads to the 9'-8" × 9'-0" bedroom, which is separated by a wall so the sleeping area stays private. The 7'-8" × 5'-1" bathroom and a 2'-5" × 3'-7" stacked laundry complete the plan.
Layout highlights
- 410 sq ft of living space on one level, with no stairs
- Compact 19'-8" × 23'-0" footprint for a detached backyard unit
- Living room of 8'-10" × 11'-7" opens to the kitchenette
- Bedroom of 9'-8" × 9'-0" is separated from the living area by a wall
- Stacked laundry in 2'-5" × 3'-7" beside a 7'-8" × 5'-1" bathroom
Room sizes
| Room | Size | Area |
|---|---|---|
| Kitchenette | 7'-8" × 6'-4" | 49 sq ft |
| Living Room | 8'-10" × 11'-7" | 103 sq ft |
| Bedroom | 9'-8" × 9'-0" | 87 sq ft |
| Hall | 4'-10" × 3'-7" | 17 sq ft |
| Stacked Laundry | 2'-5" × 3'-7" | 9 sq ft |
| Bathroom | 7'-8" × 5'-1" | 39 sq ft |
Who this plan suits
This plan suits homeowners adding a rental, guest suite or space for a family member in a rear yard. It needs a level or gently sloped lot with room for a 19'-8" × 23'-0" footprint plus the setbacks your jurisdiction requires.
How this plan was made
It was generated in AI Architectures Plan Studio from this one-line brief: “Detached backyard ADU (accessory dwelling unit) with about 400 sq ft of living space: 1 bedroom, 1 bath, studio-style open bedroom area separated by a wall, kitchenette, stacked laundry.” An AI architect drafted the room program, a layout solver placed every wall and door, and the plan was checked automatically for room sizes, circulation and daylight. The same project produced the PDF sheets, layered DXF, IFC model and 3D model you can download above.
Frequently asked questions
What are 400 sq ft ADU plans?
They describe a small accessory dwelling unit, usually detached, with a complete living space of about 400 sq ft. This version has 410 sq ft of living area with one bedroom, one bathroom, a kitchenette and stacked laundry.
What affects the lot requirements and cost of this ADU?
The 19'-8" × 23'-0" footprint must fit within your local setbacks, height limits and maximum ADU size. Cost is driven mainly by site utilities, foundation type, finishes and local permit fees, so get local quotes before you commit.
Can I change this plan by chat?
Yes. You can ask for changes such as moving or resizing rooms, switching the porch side or adjusting the footprint to suit a narrower lot. Garage options can also be discussed, though this plan has none. The layout is then regenerated with updated room sizes.
How do I use the PDF, DXF and IFC files?
The PDF is for reviewing the plan and sharing it with contractors or your permit office. The DXF opens in CAD software for drafting edits, and the IFC imports into BIM tools for coordination. Have a licensed professional review the files before permit submission.