Soundman2020 wrote:Right! Never, ever grind or cut protruding nails in roof decks. What you could do if you want to "beef up" the mass (and assuming that your ceiling is not vented-deck, and that the trusses have the load bearing capacity to support it) is to press Styrofoam panels of just the right thickness over the nails, then beef up over that in the normal way.there are roofing nails sticking through the OSB. I was going to grind them flush but was advised by a roofer not to because it weakens shingles.
Fill your air gap with insulation too, not just the framing. Completely filling the entire cavity is necessary to get maximum damping and maximum reduction in speed of sound, and therefore maximum reduction in MSM resonant frequency, which maximizes isolation.R-13/insulation / 2" air gap
I doubt that would work. How would you keep it in place? How would you seal the joints and the edges? Air-tight seals are critical for isolation. I would save your MLV for tuned traps and beefing up the speaker soffits, for example. Or return it to the store for refund.Could I put strips of MLV on furring strips in-between the scissor joists on OSB to add mass?
Very likely. That looks like a ventilated deck roof, probably with air inlets under the eaves and a ridge vent on top. That has to breathe. And therefore cannot be the outer-leaf of the MSM system. Sometimes you just have to go three-leaf.It looks like your "attic" need to breathe.
That would work, but it would be complicated to do with scissor trusses, due to the the angels of the various components. The modules would have to be strange shapes and sizes, with tapered framing. It would be easier / cheaper / faster to just put up OSB and a couple of layers of drywall directly on the bottom of the trusses, and seal that to the walls. That leaves the entire attic space free to ventilate, then you can build the complete inner-leaf room within that "shell". With an inside-out inner-leaf ceiling there would still be plenty of ceiling height.So your outer leaf would be inside out modules that slide up in between your joists.
- Stuart -
Yes the outer shell has air inlets under the eaves and a ridge vent on top. I thought I could use proper vents to keep a channel for air from the eaves to ridge then put drywall or MLV somehow mounted to the scissor joists and then fill the cavity with insulation to create a 2 leaf system. I'm realizing this may not be possible now after reading your comments. If I went the other way as you stated with OSB and a couple of layers of drywall on the bottom of scissor joists how much low end isolation do you think I would lose?
