Measuring a homes square footage | Caution!

Posted by Jace Stolfo on Monday, September 1st, 2008 at 8:41pm.

Did you know references to homes square footage are actually just estimates? A homes square footage, one of the most basic principles of a homes value, can easily be miscalculated if not done by a professional. Even then, the measurement is still subject to human error. As a Realtor, I see it often and can tell you these discrepancies can significantly affect a homes value.

Why are there discrepancies on square footage measurements?

1) The question of what to include: While appraisers will use the ANSI standard (see below), others may include areas that should not be calculated. For example, a basement with low ceilings, an attic with sloping ceilings, pop out windows, etc. If you are purchasing a home, be sure to ask about the square footage source. In the Boise MLS, agents are required to state where the data was obtained.

ANSI Standard Basics:A copy of the complete 16-page ANSI measurement standard is available at • Homes are measured from the outside of the walls. • Include only finished areas. • Do not include openings in floors. • Include stair treads. • Ceilings height minimum 7' except under stairs, beams, and sloping ceilings. • Do not include the garage.

2) Human error: Measuring the square footage for one story homes is fairly simple, but when measuring a large home with unique architecture it becomes more challenging. To illustrate this point, recently I was in a broker valuation and analysis class with approximately 30 other agents and we went out to measure a home under construction. While some calculations were very close, others were over 20% incorrect.

What source can you trust? Ultimately, NO sources are guaranteed and all references should be considered approximate. It's up to the buyer to satisfy themselves to the size of the home. I recommend evaluating the various sources and seeing how much they are in agreement.

1) Building plans. There are two main issues with building plans for square footage reliability. First, you have to be sure you have the final version because they are often changed several times. Second, that the home was actually built according to the plans.

2) Appraisals. Besides having the correct building plans, I personally believe appraisals will reflect the most accurate measurement.

3) County records. While usually minimal, I often see inconsistencies with building plans and appraisal measurements.

4) Real estate brokers. In my opinion, do not rely on, as the story earlier illustrated.

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