Does a basement count as square footage in New Mexico?
No, a basement does not count as square footage in New Mexico.
Not as gross living area, in New Mexico or any other state. ANSI Z765, the measuring standard Fannie Mae requires appraisers to use, puts a basement in below-grade area because part of it is under the ground. A finished basement is reported on its own line; an unfinished one is not living area at all. New Mexico has no rule of its own that changes this.
Why a basement is not gross living area in New Mexico
The line is drawn by grade, not by finish, windows, or how the space is used. Under ANSI Z765 any level with part of its floor below ground on any side is below grade in its entirety. That covers every basement, including walkouts and daylight basements, and it covers them the same way in New Mexico as in every other state.
An appraiser still measures the basement. Finished area goes on the below-grade line, unfinished area is noted as unfinished, and each is valued separately. What never happens is the basement being added into the gross living area of the house.
Basements in New Mexico homes: the numbers
Basements are rare in New Mexico. Only 4% of single-family homes in the state sit over one, against 43% nationwide, according to the 2024 Residential Energy Consumption Survey. Most New Mexico houses are built on a slab or a crawl space, so the question comes up mostly with older homes, hillside lots, and houses bought in other states.
The average New Mexico single-family home has 1,843 square feet of total area, basement included, compared with 2,248 nationally.
| Single-family homes | New Mexico (2024) | United States (2024) |
|---|---|---|
| Have a basement | 4% | 43% |
| Basements that are finished | Not available | 59% |
| Owners who count the basement in their square footage | Not available | 40% |
| Average total area, basement included | 1,843 sq ft | 2,248 sq ft |
Source: U.S. Energy Information Administration, Residential Energy Consumption Survey. Values are for single-family homes; a small number of states have samples too small to report every line.
Calculator: what a basement adds to a New Mexico house
Enter the basement area and the above-grade area. The first figure is the gross living area an appraiser reports; the last is the inflated number a listing shows when it adds the basement in.
The basement does not count. The appraisal GLA stays at 1,800 square feet. A listing that adds it in would show 2,600, which overstates the house by 44%.
How West basements changed since 1971
New Mexico is in the Census Bureau's West region. In 1971, 15% of new single-family houses completed in the West were built with a full or partial basement. In 2025 it was 16%. Nationally the share went from 36% to 16% over the same years, as slab and crawl-space construction spread.
What to put on a New Mexico listing
Report the above-grade area as the square footage and the basement on the below-grade or "finished basement" line your MLS provides. Most New Mexico listing systems have separate fields for above-grade, below-grade, and total finished area. Filling in the total field is fine; presenting it as the size of the house is what causes appraisal gaps and, in some states, complaints.
If a buyer's appraisal comes in with a smaller number than the listing, this is almost always the reason. The house did not shrink. The basement moved to the line where ANSI Z765 puts it.
Frequently asked questions
Does a basement add to square footage in New Mexico?
It adds value and it adds below-grade finished area, but it does not add to gross living area. New Mexico appraisers follow ANSI Z765 because Fannie Mae requires it, and that standard keeps every basement on a separate line.
Do New Mexico appraisers count a basement?
They measure it, report it as below-grade area, and value it with its own adjustment. They do not count it in GLA. There is no New Mexico exception to the standard.
Does Zillow square footage include the basement in New Mexico?
Often, yes. Zillow and county records frequently show a total that includes finished basement area. An appraisal will show a smaller number because it reports above-grade GLA only.