One small part of what real estate appraisers do is measure homes
to calculate the living area or “square footage.” The standard that is typically used by most home appraisers to measure and calculate living area is provided by
ANSI (American National Standard Institute). However, in this post
I’m focusing on the geometry and simple math of determining the total area.
Normally, appraisers draw homes using software that automatically calculates the area. Our company recently measured a home of an engineer by using just such software. After examining
the computer generated home sketch, the engineer said that the upper level of his home (shown in the illustration above) had been incorrectly calculated. He then provided his handwritten calculations as support.
When I heard this, my stomach knotted up and I thought, “Did this engineer find a bug in our software?” A Quality Appraisal associates measure many homes each year all around the Portland
area. I thought, “Is this an isolated bug or something that could have caused errors in hundreds of appraisals or measurements?” We don’t manually check the calculations of the software on all of our measurements before they are delivered to a client. Maybe
I could not wait to get back to my office and check for myself. Once in the office, I deconstructed the drawing into five smaller shapes (a composite figure and some appraiser software
will do this automatically) and then I was able to easily calculate the area as shown in the figure above. To my relief, I came up with exactly the same number as the software total for the upper level. After this experience, I concluded it is good practice
for appraisers to occasionally check the calculations totaled by our sketching software. For more information on how to deconstruct a composite figure and add up the individual areas, here is a short helpful video from Mathtrain.TV.
Did I leave anything out or do you want to join in the conversation? Let me know in the comments below.
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