If the property marketing matches the tax records and there is bonus space the appraiser can place a modicum of value but not as much as if the space was permitted and appearing on the tax records. In other words if the comparable 2/1 house sold for $400/SF and this unwarranted space added 200 SF it would not add $80,000 to the comparable value.
Biggest key is for the buyers to be aware of what they are buying and to infomr the sellers that times have changed - they should have pulled permits. Then take full advantage of the seller to get the space for your buyers at the current market discounted rate.
Lesson should be - get permits and don't do work that isn't allowed.
It makes disclosures easier on the resale side, and we can get a higher price after we flip it.
Lynn911 Dallas Realtor & Consultant, Loan Officer, Credit Repair Advisor
The Michael Group - Dallas Business Journal Top Ranked Realtors