We were reviewing a loan with property located in a SFHA. We do have flood insurance on the home, but we just discovered that there is also a shed on the property. I will be addressing our procedures to avoid this miss going forward, but I'm stumped on how to resolve this one. The appraisal has no value for the shed. We contacted the appraiser but he says we did not request a value for the shed in our scope request (we didn't know it existed) and he does not have the dimensions to calculate a value. The hazard insurance policy has no mention of any structure other than the home. The town assessment has no mention of it either. So what options do we have at this point to determine the value? Can we ask the customer for dimensions? If so, what cost do we use to calculate replacement cost? Do have to hire another appraiser?

I would speak to the insurance agent and see if they are insuring the shed on a schedule - what value they have for it.
Note: The new Homeowner Flood Insurance Affordability Act exclusion #13:https://www.govtrack.us/congress/bills/113/hr3370/text

Your shed issue most likely will be mute when this goes into effect.

Well, technically that is now part of the actual law and should have been effective the day the President signed the bill.