How do I measure the square footage in my house?

plans and measure tape

Sometimes, when neither an informal meeting with the staff at the Central Appraisal District (CAD) nor a formal hearing with the Appraisal Review Board fail to produce an acceptable result for a taxpayer, arbitration nor litigation is an option.  Last week, I received a call from an attorney who specializes in representing property owners in litigation matters. While square footage differences are not usually the subject of litigation, in his case, it was an issue.  His client was an architect and she maintained her house was much smaller than the CAD’s records. His question to me was, “How do appraisers determine the square footage of a house?”  While you may think this is an easy question on which there would be general agreement on the methodology, that is not always the case.

Some guidance can be found in a document created by The American National Standards Institute (ANSI) some 25 years ago. The guidelines are voluntary, but most appraisers in private practice follow them. We won’t go into all the special cases in this blogpost but let’s cover just a few of the major issues.

  1. What is measured — Inside dimensions or outside dimensions? Back to our architect friend. Her contention was that the square footage was the area actually inside her house. While that may be what is needed sometimes (i.e. – how many square feet of carpet or wood flooring do I need), for appraisal purposes, square footage is measured from the outside dimensions and includes the wall studs and the brick or outside skin (yes, your square footage will be greater for a house with brick on the outside than for a house with wood siding). A good way to think of it is, “the footprint of the slab.” Upper floors are measured from the inside and wall thickness is added. Note – condos are a different animal. Since with a condo, you only own the “airspace” and not the exterior walls, condos are generally measured from the inside without adding for exterior walls.
  2. What about garages, patios, porches? For valuation purposes, Square Footage is only for living areas and must be air conditioned space – so garages, porches and patios do not count.
  3. What about converted garages, room additions, enclosed patios, etc? Here, it really depends on the quality of construction of this converted space. If it is the same quality as the main house, under the original roofline, accessible from the main house without going through the garage or outside, and air conditioned like the rest of the house, it may count as full living area. But frequently, these additions and converted spaces are not the same quality, are obviously not part of the original house, and therefore, should be counted separately. They may contribute value but at a lessor rate.
  4. What about open areas upstairs and the stairway itself? There is no disagreement on open areas – they do not get counted. But the stairway itself gets a little tricky. While the ANSI standards state that the stair treads should be included in with the second level (like a hallway), most builder plans do not include the stair treads and consequently most of the public records for square footage do not either. If the purpose of calculating the square footage in the subject is to compare with the square footage shown in the public records of other properties, to be consistent, most appraisers and appraisal districts do not include stair treads in the square footage.

These are a few of the main issues we face with square footage measurements. We do not recommend you measure the house yourself. Instead, call a certified appraiser. Of course, if you want the appraisal district to come and re-measure, they will. But that can sometimes create a new problem. If you’ve recently remodeled or have a pool the district does not know about, we suggest you read our blogpost, “Let Sleeping Dogs Lie”.

If the district has the square footage of your house is a little heavy and you just want to let that sleeping dog lie, we still suggest you protest the value every year. The new deadline is April 15 in most cases. To make sure you don’t miss that deadline, sign up for a reminder from at the right.

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