We have a large commercial building as collateral that has had a firewall installed in order to sell off a portion of the building. Does a firewall consider buildings to be separate and therefore require separate flood insurance policies? Would this situation be similar to condos that are not covered by RCBAP policies?

I do not believe that a firewall alone would make it two separate buildings. However, if the buildings are going to be separately titled and can be owned and sold separately, the fact that they have a common wall would lead me to believe that they would be required to be separately insured. The fact that they can be separately sold does not make them condos.

A solid wall only really comes into play when you are talking about an addition or extension to a building, then the standard NFIP policy has the following to say:

Additions and extensions attached to and in contact with the building by means of a rigid exterior wall, a solid loadbearing interior wall, a stairway, an elevated walkway, or a roof. At your option, additions and extensions connected by any of these methods may be separately insured. Additions and extensions attached to and in contact with the building by means of a common interior wall that is not a solid load-bearing wall are always considered part of the building and cannot be separately insured.