Not So Small: Did You Know there are Building Code Requirements for Minimum Room Sizes?

RTAblog_0720_tinyroomLate last week, we published a blog post about the discussion of smaller apartments – some proposals are just 250 square feet. That post generated a few questions about the minimum allowable room sizes so here are some notes…

Residential construction for single-family homes is governed in many states by the International Residential Code (IRC). The IRC is published by the International Code Council and has been adopted and amended by states and local jurisdictions. Chapter three of the 2012 IRC, titled “Building Planning” includes some minimum areas and clearances.

Section R304 “Minimum Room Areas” governs habitable spaces. “Habitable” means you can live in the space. By definition, that excludes spaces like bathrooms, closets, halls, storage spaces and other areas in which you can’t live.

Section R304 calls for every dwelling unit to have at least one room no less than 120 square feet of gross floor area. There’s also a minimum dimension of not less than 7 feet in any horizontal direction. That means there must be at least one room that’s 7 feet by just over 17 feet.

The same section also allows other habitable spaces to have a floor area of not less than 70 square feet. With the same minimum dimension requirement, that means other rooms can be 7 feet by 10 feet. Kitchens are excluded from both the minimum room requirements and the minimum horizontal dimension requirement.

There are also minimum requirements for ceiling height in Section R305. In summary, the minimum ceiling height is 7 feet although there are some exceptions for sloping ceilings and bathrooms. There’s also a section on basements that don’t have habitable space that allows a ceiling height of 6 feet and 8 inches with an exception for beams and other obstructions that can be slightly lower, at 6 feet and 4 inches.

As always, we hope this is helpful. Leave a comment or use our Ask an Architect tool if you have any questions. Thanks!

Photo by ElCapitanBSC used under a creative commons license.

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