The real issue is, no lender is *ever* required to lend to you: it is voluntary for lenders to issue mortgages, and a lender can refuse to lend to you if they feel it is a bad deal or poor risk for them. Also, no seller (e.g. the bank) is *ever* required to sell to you if they feel it's not worth doing so for some reason (too low a price, bad risk, too complicated and too much effort, etc.) Therefore, it doesn't matter what some other definition (e.g. a definition of anyone but this bank) of "unimproved" is: all that matters is that the bank with which you are dealing appears unwilling to go through with your proposed transaction: you can keep negotiating with them and see if you can get them to change their mind, but regardless of the definition of "unimproved," you can't force them to move ahead with you.