The appraiser pulls comps and then srives by the property to view the condition of the exterior only. They take a picture of the front of the house and that is it. These are not done often now. I have been able to get a drive by on my investment property when I am refiancing, usually onto a line of credit. FHA does not allow these. Conventional loans with excellent credit and a significate downpayment may depending upon the lender. They are generally less expensive than a full appraisal.

Ward a drive by is where the appraiser does not go into the home but just drives to it and takes a picture without having to get out of their car. These are never done on an FHA loan. Conventional loans used to allow them in our area depending on the lender.
A lot of the time they are used for a refi or equity line loan.

Hi Ward
A drive by exterior appraisal is just what it sounds like....an appraisal where the person performing it does not access the property.
Typically we are not experiencing these right now in the true appraisal process. More likely you are referring to a BPO (Brokers Price Opinion) that is done by a Realtor at the request of a lender servicing the mortgage on the property. This could be something the owner generates seeking a loan modification or a preliminary "watch" to a pre-foreclosure or foreclosure process. If the property is occupied, the lender will not disturb the occupants, but rather do preliminary information gathering to help determine factors involving the loan on the property.
Hopefully that answers your question.

It is a simple valuation that is done based on exterior condition. Typically it is not an appraisal but actually a valuation done by a real estate agent. These BPOs (broker price opinions) are typically ordered by lenders to get a basic idea of value on properties going into foreclosure. They don't want to bother the borrower so they just have an exterior or drive by valuation done.

Make sense?