Qualitative Sales Grid
The single-family sales grid is quantitative. The adjustments there are all on a per square foot of living area basis. Quantitative analyses work well IF AND WHEN sufficient market evidence exists from which these adjustments can be abstracted or reasonably estimated. You must also have to have the time and training to develop and support a quantitative grid.
Single-family evaluations typically lend themselves to quantitative analysis because of a sufficient number of available sales. Commercial fee appraisals also often make use of quantitative analyses because they have the time and fees to support the effort.
Unfortunately, tax agents seldom have the time to locate a sufficient number of confirmed commercial or other types of sales and create supportable quantitative adjustment grids.
Alternatives?
Qualitative sales grids have been an acceptable and widely used method of sales comparison for decades, and sales remain a desirable and practical approach to valuation.
When equivalent sales are not available, get two or three sales that are superior to your subject property. Get a couple of sales that are inferior to your subject property. With these sales, you have just established a range of values between the superior and inferior sales within which your subject property value is likely to fall.
A qualitative grid does not use or rely on quantitative adjustments. Rather, you identify the similarities and variances that impact value between each sale and the subject property.
The final conclusion for each sale is the overall impact of variances. You might conclude that the variances offset and the sale is, overall, equal to the subject property. You might also concludes that, overall, the sale is vastly superior, superior, inferior, or vastly inferior to the subject Property.
The identification of variances and ratings narrow the value range and provide a rationale for your final value conclusion.