So you might think that you can just add all your measurements up, complete the calculations and be done, right? Not so fast -- that's how square footage can be confusing in the first place. It turns out there are several areas that shouldn't be included in your calculations.
First off, there's the matter of ceiling height. While you're not measuring the three-dimensional area of a room (length x width x height) to get your overall square footage, in order for a room to be included in the total square footage of a house, the ceiling must be a certain height -- so that crawl space doesn't count. To count in the square footage equation, a ceiling must be 7 feet (2.13 m) tall, or 6 feet 4 inches (1.9 m) with beams or any thing else that might hang down. If the ceiling is angled, it must be 7 feet or higher for at least half of the room's floor area. If it is, then any part of the room with a ceiling of 5 feet (1.52 m) or higher should be included [source: Boddy]. If not, you shouldn't include any of that space.
As for rooms in the house that aren't finished, like basements or attics, they should not be included in the total square footage. In fact, any part of the house that is below ground level -- even if it is only partially so -- should not be included under any circumstances. Even if it a basement area is finished -- which is to say that it is heated the same as the rest of the house and could be lived in year round -- it doesn't count according to ANSI. In the past, many basements were counted as long as they had windows. However, ANSI needed a universal standard and as a result, basements were eliminated completely from their standards for calculating square footage [source: Williams]. Porches may only be included if they are enclosed and heated using the same system as the rest of house. As for lofts and attics, the ceiling rules still apply, and you can only include them if you can reach them by stairs. Any part of a house that requires the use of a ladder to get to it doesn't count.
Outside, garages are not included, period. If the garage is attached to the house, the shared wall will serve as the outside wall of the house when determining square footage. The same goes for guesthouses, pool houses or any rooms that require you to leave the finished area of the main house to gain access. Whether they are finished or not, they cannot be included in the square footage of the main residence [source: Boddy]. They should be reported as "bonus rooms." However, if you have a finished area above an attached garage and you can get to it without leaving the house, go ahead and count it.
While these rules are widely accepted, you'll always want to ask what standards were used to determine the square footage of a house. They may differ from realtor to realtor. If they used different standards, don't be afraid to ask for a detailed explanation of how the square footage was determined.
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