I have a 2 story + basement townhome with 8" concrete blocks walls between my neighbors. At the top of each shared wall is a sheet metal cap. Some of the cavities have concrete in them but many are completely open from the basement to the roof.
- Was this a cost savings approach by the original builder in the 1970s or is there a reason to keep some of the cavities open?
- Assuming it's safe to seal these up, what materials can be used to seal them? e.g. concrete, or a boat load of closed cell foam.