I recently did a retrospective appraisal for estate purposes on a property that had, since the effective date, been demolished & completely re-built. It was pretty much based 100% on past plans & specs. Most retrospectives are, in one way or another.
Would it be based on owner's request or accountant or???
You certainly can. Remember there is no USPAP requirement to even inspect the subject. Since this is an estate appraisal (Intended Use unknown-you didn't say in your post), no supplemental standards apply. Yes you certainly can do an exterior only inspection and base your report on that.
The real question you should ask is this: Do you really want to do an exterior only based on the clients needs and the Intended Use of the appraisal?
Using an exterior inspection for an estate which I would assume (EA permitted since this is not a FNMA controlled post) is to estimate value as of a date certain in the past which was the date of death or to set a selling price. In these two cases, the degree of accuracy required by the Intended Use is such that your SOW would normally require a full inspection of the subject. You certainly can come up with a value doing an exterior only inspection but there could be so many unanswered questions as to make your appraisal useless to the client.
Your appraisal should solve a problem for the client; not create additional problems.
I personally would not do an exterior only for either of the two Intended Uses listed above unless there were some really overwhelming reason and then only very reluctantly with lots of warnings to the client.
I would think an estate may be one of the places that a driveby may be necessary when there may be feuding heirs. If you can gather enough data about the property to make your report credible ... and you specifiy all in the scope of work and make the necessary assumptions ... I dont see why you cant do it. This may be one of those special circumstances where the report type is appropriate ... at least in my mind, what little there is left on Friday Morning.
Credible results! Can you obtain them without an interior inspection? Depends on you Scope of Work.
I just got off the phone with an appraiser in Denver who received a call from a para-legal asking if he would bid on 70 properties for "estate purposes". She said she got a bid of $50 per property and was looking for a lower one. Guess what I told him?