John Sayers' Recording Studio Design Forum Archive

consider m1 as your inner mass boundary, and m2 as your outer mass boundary. make those as dense as needed by your isolation needs. so if 2x gwb + GG will suffice, then do that, or maybe 3x m1 and 3x m2, etc. the inclusion of the GG should be decided by weight restrictions and budget. if it's less expensive and weight wise ok to do 3x gwb then i would go there. if weight wise you need to use GG to get that extra isolation, and you have the budget, then go there.

Ok thanks Glenn. What do you think of having the new inner ceiling rafters not touch the existing ridge beam? Is it worth doing that to avoid another flanking path?

i think you can attach them as they're attached to the existing structure anyways. the inner room is where you want to decouple as much as possible.