Ida, I had originally thought I might plagarize your quote,and so I cut and pasted it to my word processor. However, the more I thought about it, the more it seemed to be not quite right, or more speciffically, not quite complete. Taking your original thought, I reworked it, and here's what I came up with:
"Incurable physical depreciation is based on the estimated effective age of the subject, which takes into consideration the actual age and expected remaining life of the improvements. The percentage of physical, incurable, depreciation applied is based on the estimated effective age of the structure divided by its most probable economic life when new. Although, generally considered incurable, replacement of major component items such as roof structure, windows, siding, heating and cooling systems, wiring, or plumbing may extend a property's expected life and lower its effective age.
Condition adjustments are generally based on curable physical depreciation issues and take into consideration the general overall condition and maintenance of the improvements. Replaceable items such as paint surfaces, roof cover, floor coverings and similar parts of the structure considered to be maintenance items can affect the condition. If there is curable physical depreciation, it is estimated at the cost required to correct the deficiency. Properties that have been maintained with care may be in better condition than properties that have not been well maintained, regardless of effective age.
Effective age and condition are separate issues in the appraisal process. Improvements that are the same actual age and approximately the same effective age, may still differ in condition based on appearance and function of maintenance items.
Functional obsolescence can be curable or incurable and it accrues from factors or features within the property that affect the property value in a negative way. Included in the factors or features that affect the property negatively are poor design, either inadequate or super-adequate construction, and numerous other possibilities. When possible, curable functional obsolescence is measured by the cost to cure the deficiency; incurable functional inutility is measured by the rental loss that accrues by reason of the deficiency.
External obsolescence, if any, is caused by factors outside the property and is usually not curable. When possible, it is measured by the loss in rents accruing from the presence of the depreciating factor or condition."
Mr. Henry, in fact it is quite possible to get accurate depreciation from the market for almost any property regardless of age. If you calculate cost new (reproduction) on any property that is a sale you can easily calculate total depreciation for that specific property. (Don't forget that land doesn't depreciate when doing the calculations.) That is the math. Getting out the part of the total depreciation that is due to effective age from what is attributable to other causes; well, that is the art. (Hint: Doing a replacement cost calculation can sometimes help with this.) But, here's the point: If you do it time after time, assignment after assignment, you will eventually gain a pretty clear insight as to what to attribute to physical depreciation on almost any property. Or, you could just do it by the book, like Ter. I have found Marshall & Swift to be incredibly accurate when used correctly.
