Best ADU Floor Plans by Size

After enough projects, floor plans stop being infinite possibilities and start being patterns that work. Here are the proven patterns at each size — and why they win.

400 SF — The Open Studio

Pattern: One open volume; kitchen along the back wall; bathroom and closet stacked in one corner; sleeping alcove or partial wall opposite the entry. Why it works: Plumbing lives in one corner (cheaper), the main space stays whole (feels bigger), and the bed is out of the entry sightline (feels like a home, not a dorm). Avoid: chopping the space into a "real" bedroom — you get two bad rooms instead of one good one.

600 SF — The Classic One-Bedroom

Pattern: Open kitchen-living across the front (windows and entry), bedroom and bathroom across the back, stacked laundry in a hall closet. Why it works: Public rooms get the light and the entry; private rooms get the quiet. One short hall (or none). Plumbing groups on one wall. Avoid: center hallways — at this size, a hallway is 8% of your house doing nothing.

800 SF — Two Proven Variants

The Grand 1BR: oversized living-dining with island kitchen; large bedroom with walk-in closet; bathroom with tub and shower. Feels like a boutique small house. The Efficient 2BR: bedrooms on opposite sides (privacy between them), shared bath centered between, open living core. The "roommate plan" — each bedroom gets a corner with windows on two walls. Avoid: the 2BR with both bedrooms sharing a wall — you've built one private bedroom and one echo chamber.

1,000 SF — The 2BR/2BA House

Pattern: Primary suite (bed + bath + closet) on one end, second bed and hall bath on the other, open kitchen-living-dining in the middle, laundry closet central. Why it works: The living zone acoustically separates the bedrooms. Two plumbing zones, but each is compact. This is the most-requested rental plan we build.

1,200 SF — Going Three Bedrooms or Going Up

At the typical detached maximum you can do a single-story 3BR/2BA (tight but real) — or a two-story 2BR that keeps footprint near 600 SF for small lots. Upstairs plans: living up (light, views) or sleeping up (quiet, conventional); pick based on what surrounds the lot.

The universal rules

Group plumbing. Minimize hallway. Windows on two walls of every main room. Entry that isn't straight into the kitchen. And a wall of built-in storage somewhere — every size, every time.