The 800 SF ADU: The Guaranteed Size

800 SF is California's magic number — the size every city must allow regardless of lot coverage, floor-area ratios, or open-space rules. It's also the point where you face a fork in the road: one big bedroom or two smart ones.

Path A: The spacious one-bedroom. At 800 SF, a 1BR gets a king-size bedroom, a bathroom with double vanity or tub and shower, a full kitchen with an island, and a living-dining area that hosts actual dinner parties. This is premium-rental and comfortable-parent territory — small-apartment square footage with small-house feel.

Path B: The compact two-bedroom. The same 800 SF divides into two modest bedrooms (say 11'×10' and 10'×10'), one bath (or one and a half), and an efficient open kitchen-living area. Suddenly families, roommates, and work-from-home couples are in your tenant pool — and remember, crossing to 2+ bedrooms is also what unlocks the 1,000 SF guarantee if you'd rather grow.

Which path? Rental strategy usually favors the 2BR — "two bedroom" is a search filter that dramatically widens demand, and total rent is higher. Family use often favors the roomy 1BR — one person or couple living well beats two small rooms.

Why 800 SF became the default. It's guaranteed by law, big enough for either layout above, small enough to fit most backyards with yard left over, and — at planning-level pricing of $350–375+/SF — lands in a budget range ($280K–$320K+ for new construction) that pencils out against California rents in many markets.