This is the front of one of the units. What you may be able to discern is the number and size of voids...Some were filled but not completely. Also, the fire burned the foam but left the ledger intact and the wood bucks. They suffered heavy charring, but as the arson investigator said "fire is lazy it will burn the easy fuel first" The fire burned the foam clean off of the concrete on both sides. Most of the floor joists are in the foreground....heavily charred. The idea that the walls can be reused didn't last long on this one, they paid a hefty price to knock it all down and take it away.