Hello, team… I have to instal new siding over masonry. The customer wants Hardi-board over insulation (thickness undetermined, but probably 2-1/2″) . Q – how to attach 2-1/2″ material to the masonry? Do I assume 2x3s as vertical strapping? There is no sill to take the weight of all the siding, battens and trim, so whatever goes on has to be self-supporting. The BI has no answer re fire rating if it were Codebord or similar – I know that styro beadboard cannot be used indoors, but would it be suitable on the exterior?  Resonses appreciated.