Don,
If your state says to do it that way I will not argue. Government directions will take precedence. But, most states do not specify this. Most rely upon USPAP alone. You know USPAP well.
My point here is that USPAP says recognized methods and techniques. IF the state specifies local custom, fine. However, IF it does NOT- as is the case in most- then we have only one recognized method/technique and that is ANSI.
As to Fannie, I do not have a copy of it and it is not in the selling guide that I can find; however, they published a letter when it was done saying that they had adopted this. Note their selling guide has not been fully updated and still conflicts a bit with their own more recent appraisal guide, so you will obviously be defensible,
Just worries me when we fall back upon what is defensible vs. what may not be as easily defensible but is still right. I would bet you dollars to doughnuts that citing ANSI as your source- even in your local markets- will be as defensible or even more so than "local custom". My reasoning here is that no one can really define local custom unless ALL, or at least the overwhelming majority of, particpants do exactly the same thing- and I'l just bethca that they do not. However, ANSI is a national technique and its developers included the home builders, Fannie and NAR. Following it produces consistent results- and again, absolutely NO ONE is saying one cannot assign the same value to stuff below grade or on another level IF that is what the market does.
I am frankly surprised that so many just dismiss this. It has saved my bacon many times over in arguments with LOs, borrowers, etc.
Brad