4.4.3.6. Unit Rule and the Cost Approach.Valuations derived from the cost approach and any other approach to value must follow the unit rule, which requires property to be valued as a whole, as discussed in Section 4.2.2. Indeed, “it is firmly settled that one does not value the [ ] land as one factor and then value the improvements as another factor and then add the two values to determine market value.”579 In using the cost approach, it is therefore critical to distinguish between calculating the cost of improvements and estimating the market value of the property as a whole, considering the contributory value of improvements.580 

As discussed in Section 4.2.2.3, some assignments may require separate allocation of the contributory value of improvements that will be removed or adversely affected due to the government project (if applicable, the appraiser should clearly state that any such allocations do not indicate the appraisal method(s) employed).581