GLA - gross living area:
"The most common comparison for one-family properties (including units in PUD, condominium, or cooperative projects) is above-grade gross living area. The appraiser must be consistent when he or she calculates and reports the finished above-grade room count and the square feet of gross living area that is above-grade. For units in condominium or cooperative projects, the appraiser should use interior perimeter unit dimensions to calculate the gross living area. In all other instances, the appraiser should use the exterior building dimensions per floor to calculate the above-grade gross living area of a property. Only finished above-grade areas should be usedâ€”garages and basements (including those that are partially above-grade) should not be included. We consider a level to be below-grade if any portion of it is below-gradeâ€”regardless of the quality of its â€œfinishâ€ or the window area of any room. Therefore, a walk-out basement with finished rooms would not be included in the above-grade room count.
Rooms that are not included in the above-grade room count may add substantially to the value of a propertyâ€”particularly when the quality of the â€œfinishâ€ is high. For that reason, the appraiser should report the basement or other partially below-grade areas separately and make appropriate adjustments for them on the â€œbasement and finished areas below-gradeâ€ line in the â€œsales comparison analysisâ€ grid. To ensure consistency in the sales comparison analysis, the appraiser generally should compare above-grade areas to above-grade areas and below-grade areas to below-grade areas. The appraiser may deviate from this approach if the style of the subject property or any of the comparables does not lend itself to such comparisons. However, in such instances, he or she must explain the reason for the deviation and clearly describe the comparisons that were made
Then there is Gross Building Area or GBA: Gross Building Area sometimes can be the same as GLA (Gross Living Area) and is especially true for single family homes. However, in a multi-family residence there maybe common areas that would not be considered living areas, but part of the size of the structure. "