1.2.7.3.2. Unit Rule. There are several aspects of the unit rule that are important for appraisers to understand in developing appraisals under these Standards. The unit rule requires valuing property as a whole rather than by the sum of the values of the various interests into which it has been carved—such as lessor and lessee, or life tenant and the holder of the remainder. This requirement holds true in circumstances where the physical components of the property are held under different ownership such as the surface estate, mineral rights, water rights, or timber. Even when the physical components of a property are under the same ownership, it is improper to separately value the various components (improvements, minerals, standing timber, crops, and land) and then add them up. This procedure results in an improper summation or cumulative appraisal, which is inconsistent with both federal appraisal standards and USPAP.28