Do you ever get those questions? “Well ABC appraised my house last year and my house was 3,726 square feet. Why do you say it only contains 3,698 square feet?”. I have always wanted to say, well as your house gets older, the wood begins to shrink… Everyone knows of course that houses come in different sizes, shapes and that walls can be built at angles other than 90, 60 or 45 degrees, thus accurate measuring can be a challenge. When you factor in roof pitch for upstairs rooms, or many shrubs, or rose bushes or other obstacles around the perimeter, any given measurement can be off by a few inches one way or another and then you take the variance of a few inches and multiply that by a run of 45 feet or more. The estimated house size can easily vary due to the different methods that are used to measure the home as well.
Many old timers, like me, still use a 100′ steel tape to measure the exterior perimeter of the home. There are, of course, several alternatives available today: steel, fiberglass, and vinyl measuring tapes. There are also measuring wheels, and sonic and laser measuring aids. There is no one device that is better or more reliable. However, you must understand the degree of reliability that each device offers before you decide to use it to determine size. For instance, the measuring wheel can skip when it encounters rough terrain. The sonic device may give false readings if there is an obstacle between you and the wall that you are measuring. The laser sight can find interference from direct sunlight, or can give false readings if an obstacle is blocking a clear path between you and the distance you are attempting to measure. A vinyl tape will stretch over time thus 1 inch becomes more than an inch. A steel tape requires maintenance to keep it from rusting and cutting your hands or fingers. The fiberglass tape and steel tape are the most reliable, in my humble opinion.
When measuring a home, the garage, porch, patios, and any non-heated or cooled space is not included in gross living area; however, these spaces are measured so that the appraiser can account for the cost of these items. Additional flatwork, or extra concrete (i.e. driveways, parking pads and the like are also measured for the cost approach). Finished attics can be included if properly finished, including venting for heating/cooling. The pitch of the roof can inhibit the space which is counted due to clear space (overhead). Generally speaking, any space below 3′ is not considered habitable space. Also when measuring a second floor, many appraisers will measure the interior walls of each room and add the space together. This is practical for a small condominium or other type dwelling that does not have a lot of space; however, it is not a practical approach because interior walls should be included in the GLA. In other words a 12 x 12 bedroom right next to a 12 x 12 bedroom (i.e. 144sf + 100sf) will not equal 288 square feet of gross living area. Why? Because there is a 5-1/2 inch wall in between the rooms and exterior walls on each side of the room. Therefore, this span is actually 25.37 x 12 or 304 square feet. How can this space be added to gross living area?, I have been asked this time and time again. Let me ask a question though. When a home is built, do you believe these walls are simply built without cost? Of course there is a cost, and the only proper way to account for cost is to include the space at the time of measuring.
The accepted method of measuring a home is the ANSI method; however, there is no law that requires an appraiser to use this method. The law, USPAP, requires that an appraiser communicate the appraisal report in a way that is not misleading; thus as long as the sketch is presented in a way that is easy to follow, and the dimensions that are presented are reasonably accurate, the appraiser has met the intent or spirit of the law.
Keeping in mind the variables that can come into play when measuring a house, it is understandable why no two appraisers are likely to arrive at the same square footage estimate unless the house is a basic shape, with no angles, no fences, no shrubs and no pets. Any of the oddities or variables can cause appraisers to write different findings, and different findings will cause different results.
All of this being said, appraisers should be able to agree within 10% of size each and every time. If a sketch is off by more than 10%, there is a distinct possibility that someone is in error.
See you around the water cooler!