If you are referring to the standard for measuring houses, yes I am using it.... with one exception.
The standard calls for the stairs area to be included in the upper level to which it goes. You would therefore subtract it from the lower level. In most cases, I find this a pain not only to do but also to remember it in the first place. Therefore I have taken to ignoring this particular aspect. IMNSHO, it is a trivial thing and I am sure the square footage of the comps did not take this into account.
I am using it, but like Richard I usually don't go to the trouble of subtracting out the stairs.
There are however, several things in the standard with which I don't agree. One of the most prominent is the part where you don't include a fireplace on an exterior wall. Since you do include interior fireplaces, I feel like exterior ones should also be included. (But I don't - I follow the standard.) I got into a long running argument with the instructor of the course I took on it. My logic is simple; economically it doesn't make sense. If you are including the interior fireplace in the GLA in the cost approach and then also adding in for fireplace, then you are not treating it the same as an exterior fireplace, which is not included in the GLA. It becomes even more clear when the exterior fireplace extends into a garage. In that case, the fireplace square footage actually gets counted in the garage space, which makes no sense at all. Like I said, I'm following it, but I don't agree with it. The standard should be chaged to read that the fireplace area is included in the house size on any level where there is a firebox opening.
The other thing I don't agree with is the way they handle bay windows. But that's another story.
By the way, I do completely agree with the way the standard says to handle second level (or higher) space when the eaves of the roof come down to less than five feet of standing room at the sides of a room.
Okay, so I'll bet the standards writers don't give a hoot for my opinion. At least you would think they could make standards that make good economic sense.
I'm not sure I understand that fireplace thing. Do you not count a fireplace on an exterior wall as part of that wall's linear measurment? Most fireplaces are about 5 to 6 feet wide and take up that much room on a linear wall. Guess I'm just confused.......
I think the rule is that you don't count the "bump out" on the exterior wall as Living Space. If the fireplace is contained within the walls, such as a center living room fireplace, then it is counted.
I find this a moot point, as I never have put the bumpout fireplace in the sq. footage. I find it hard to believe that a family could "live" within the confines of a fireplace. Apparently some appraisers counted the chimney chase on the outside of the houses as part of the living space when we were measuring footprints.
I try to follow it as written, however, I also disagree on several issues, i.e., fireplace and stairs. Like anything else, "it ain't perfect" but it least it's an attempt at standardization in determining living area. One of my concerns is that home designers, architects, and local governmental personnel seem unaware of the standard. Useage appears to be spotty.