I'm going to have concrete block exterior walls now instead of a timber outer.
Smart move! That, right there, gains you significant isolation. Just remember to seal the inner surface of the blocks before putting up your inner leaf. Concrete, brick, and most masonry surfaces in general are porous, which means that air can move through them. If air can get through, so can sound. So seal the surface with a good masonry sealant.
I've asked him to dig down as suggested here to give me more interior height.
Another smart move! You won't be sorry. Yes, it is additional expense, but your resulting studio will be much better for it.
The interior decoupled room within a room will be a timber frame with double layer acoustic board as before (walls and ceiling).
Forget using specialized and expensive products that you don't need, like "acoustic board". Just use ordinary drywall. Sound waves cannot read the price tags on your mass-building materials, so they won't be impressed if you bought really expensive mass. They just react to the mass, pure and simple, so get the least expensive mass that will do the job. I normal go with one layer of OSB directly on the stud faces, then one or more layers of fire-rated drywall over that. OSB is similar in density to drywall (a little lower, but not much), and having that as your base layer means that you not only get good mass, but also a nailing surface around the entire room! So you don't have to hunt for studs when you need to nail or screw some piece of treatment in a certain place. Make the OSB thick, and you can hang whatever you want on it. It is also structurally much stronger than drywall, so you get excellent sheer strength in your walls. Etc.
I'd appreciate help on the the exterior roof. My budget definitely won't stretch to a concrete roof.
I would recommend beam and block. It's cheaper and simpler than trying to pour a concrete roof, and keeps the mass of the walls, so you get a consistent high mass, high surface density shell around you. Great isolation.
Should I tile it and have acoustic board above the rafters (or will OSB suffice). Then there'll be my gap - within insulation - before the inner ceiling of double acoustic board as above. Will this be sufficient mass? How can I beef it up if needed?
Do the math!
:) You have the equations.... Work through it, to make sure that the mass and the air gap are correct for the MSM resonant frequency that you need, and the isolation that you need. And remember that the TOTAOL isolation of your studio is only as good as the weakest part. So if you have great walls, fantastic doors, wonderful windows, top-notch silencer boxes, but a lousy roof, then your overall isolation is lousy... and you wasted a hell of a lot of time, money, and effort in all the other things....
Also, on the exterior block walls, my builder is talking about putting batons on the outside of the block, and putting timber cladding on them.
You could do that, yes, but do the math here too: you'd be creating a 3-leaf system, so there is a potential (low probability if you have concrete block walls, but still not zero probability!) that there will be an unwanted resonance issue that trashes your isolation at certain frequencies. So do the math for three-leaf systems, to check for that.
Also, you live in the UK: I would not put up a timber exterior on the building. Timber and weather do not go together well. Consider using vinyl siding, or even better, fiber-cement siding. There some really nice looking fiber cement planks that imitates wood planks, and you can seal it and stain it to get a very convincing effect. And the fiber-cement won't rot. I did my shed in the back yard like that, decades ago, and the fiber-cement still looks decent. But I used timer trim on the edges of the roof, and that needs constant attention: re-varnishing every few years... not nice.
Another option for your building exterior is plain old stucco, or exterior grade plaster. Good stuff.
OK. I've donned a second thicker skin and am holding my breath.
8) :lol: :horse:
- Stuart -