Does a finished basement count as square footage?

Published August 27, 2026

Not as gross living area. A finished basement is measured and reported on an appraisal, but as below-grade finished area on its own line, because under ANSI Z765 any level with part of it below ground, even 1 inch on one side, is below grade in its entirety. It still adds value; it just is not added to the house's GLA.

Why the basement is kept separate

Appraisers compare houses on above-grade GLA. If basements were mixed in, a 1,800 sq ft ranch with a finished basement would be compared to 3,600 sq ft two-story houses and the numbers would stop meaning anything. The all-sides grade rule draws the line in the same place for every house, which is why every basement entry in the What counts guide lands on the same answer.

What it is worth instead

The appraiser values the finished basement as a separate adjustment, typically a fraction of the per-square-foot value of above-grade space, with more for a walkout or a full bath. Listings, tax records, and Zillow often add the basement into a "total" figure, which is where the confusion starts. If you are wondering whether anything can change that, the honest answer is in how to make a basement count.

Markets that treat the basement as a lower level

In hilly areas, a lot of houses are built into the slope: the lower level is below grade at the front and fully exposed at the rear, with a patio, full windows, and a door at ground level. In those markets, buyers, agents, and the MLS often do not call that space a basement at all. They call it a lower level and pay about the same per square foot for it as they do for the floors above.

ANSI Z765 does not change for the market. The level is still reported as below-grade finished area because part of it is underground. What changes is the adjustment: where the market pays as much for the lower level as for above-grade space, the appraiser supports that with local sales and adjusts accordingly, so the value comes out the same even though the square footage sits on a different line. Fannie Mae allows exactly this as long as the appraiser explains it and treats the comparables the same way. The same logic applies to hillside home lower levels.

Unfinished basements

Unfinished basement area is reported as below-grade unfinished area. It is not living area of any kind, above or below grade.

Frequently asked questions

When can you count basement square footage?

When the level has no part below ground on any side. At that point it is not a basement under ANSI; it is a ground floor. A basement that is below ground anywhere is always below-grade area.