Small-living proponents often lament that occupancy laws make tiny houses and micro-apartments illegal. Specifically, most jurisdictions have a minimum square-footage law for permanent dwellings. (One reason tiny houses are often built on wheels is not to make them mobile but to classify them as travel trailers instead of dwellings.) But I haven’t found any compilation of what those laws actually are. So I started one myself.

The US has adopted the International Residential Code, which isn’t all that limiting: the floor area of a “habitable room” (any room in the house except a bathroom, kitchen, closet, or utility room) may be no less that 70 square feet. There is no minimum number of habitable rooms in a dwelling. The limitations increase as you zoom in, though. States may issue supplements to the IRC or reprint the code entirely. Cities add their own cutoffs, and neighborhoods may have zoning requirements that push the minimum even higher.

This reference is incomplete. I intend to grow it as I continue my research.

IRC: Minimum one 70 SF habitable room. See 2015 IRC R301.1.

Arizona: Phoenix requires a minimum of one 120 SF habitable room. See 2006 Phoenix IRC R304.1.

California: Minimum one 70 SF habitable room. For an efficiency dwelling unit, the minimum total floor area of 220 SF. See 2016 California Residential Code R304.1 and R305.1.

Florida: Minimum one 120 SF habitable room. See 2014 Florida Residential Code R304.1 .

Indiana: Minimum one 120 SF habitable room. See Indiana Residential Code R304.1.

Massachusetts: The minimum size of a single-occupancy studio is 150 SF. See 105 CMR 410.400(A).

Michigan: Supplement to the IRC does not amend minimum SF.

Minnesota: Supplement to the IRC does not amend minimum SF.

New Jersey: Minimum one 70 SF habitable room. See 2015 IRC New Jersey edition, R304.1.

New York: Uniform code supplement to the IRC does not amend minimum SF. New York City requires a minimum of one 150 SF habitable room. See Housing Maintenance Code D26-33.01.

North Carolina: Minimum one 120 SF habitable room. See 2012 North Carolina Residential Standards R304.1.

Ohio: Minimum one 120 SF habitable room. See Ohio Residential Standards 4101:8.3 304.1.

Oregon: Minimum one 120 SF habitable room. See 2011 Oregon Residential Specialty Code R304.1.

Pennsylvania: Supplement to the IRC does not amend minimum SF.

Rhode Island: The minimum size of a dwelling is 150 SF. See Housing Maintenance and Occupancy Code 45-24.3-11.

South Carolina: Supplement to the IRC does not amend minimum SF.

Vermont: Burlington requires a minimum dwelling size of 150 SF. See Charter and Related Laws 18-90.

Virginia: Minimum one 120 SF habitable room. See 2012 Virginia Residential Code R304.1.

Wisconsin: Supplement to the IRC does not amend minimum SF.

Washington: Seattle requires a minimum of one 120 SF habitable room. See Seattle Residential Code R304.1.