If you look at the blueprints of a house, the outside measurements are of the exterior part of the foundation wall. The framing of the house and the exterior siding can extend beyond the foundation wall.
When an appraiser is measuring a house, I feel it is best to approximate the foundation wall dimensions. Therefore, if a wall being measured is 24 feet nine inches long, it might be better to call that a 24 and 1/2 foot wall. Rounding back three inches would put the measurements closer to representing the exterior foundation wall, rather than the measurements of the siding. More importantly, it would be inappropriate for the appraiser to round the 24 foot nine inch measurement to 25 feet. By doing this the appraiser would be including space that is not contained in the house.
Garages and other attached or detached areas are usually measured separately. An important reason for this is that a garage usually is not finished to the degree of the living area of the house. The garage seldom has bathrooms, or kitchens and usually no finished flooring. For this reason the garage would need to be analyzed separately, therefore measured separately.
Today there are very good sketching programs that allow the appraiser to enter the house dimensions and have a very accurate representation of the dimensions of the house.
Ralph Olsen
pwas.net
