Originally Posted by niccolo
Interesting point. My concern there is that this would leave sound/vibration free to travel into the floor framing and from there throughout the house, including into the wall framing of the room below. And at this point I'm doing a low-budget build, so clips and channel aren't in the cards anywhere.
Then again, even if I put in an isolated subfloor, I'm still left with walls that are mostly coupled, and through which sound will travel. Half measures like I'm contemplating will really only yield very modest results.
Then again, even if I did a proper room-within-a-room build, on the second floor of a wood-framed house, my guess is the soundproofing wouldn't be stellar.
I think I'm going to have to live with some combination of modest listening levels, everyone in the house joining in for movie nights, or headphones.
Decision time, contractor needs to know next week in which direction I want the door hinged, even if we postpone the actual built-up floor for now. 3/4" horse stall mat is back in stock at my local tractor supply store, I'm thinking of gluing that on the existing subfloor and then gluing a layer of OSB/MDF/plywood (contractor is arguing for HDF, i.e. higher density MDF) on top of that, and maybe a second layer, maybe with Green Glue, because I think that shouldn't add too much cost and the extra mass might make a real difference. But I have to decide what to do at the door threshold. Options:
1) Build a step/landing outside the door, so the elevated theater height floor would continue just outside the door into the hallway (which is plenty wide to accommodate a step). This would involve some extra construction, and the aesthetic awkwardness of a step outside the door. But it would be building code compliant and the least trip hazard.
2) Put the step up/down at the transition, with the door hanging lower at hallway floor height, opening out into the hallway. This would be somewhat helpful from a soundproofing perspective--the door could seal against the vertical part of a carpeted step--but a trip hazard I'd have to warn people about, and not code compliant, so either the inspector would have to not care (which it appears may be the case) or it would have to be done after the inspector did their final inspection. And if I sold the home it might become an issue.
3) Put the step up/down at the transition, but hinge the door in. This would basically look like a typical front door of a house (where you have to step up a few inches to keep rainwater out of the house). It would be visually more obvious, hence less of a trip hazard. If necessary, one could always add a step or ramp outside the door later.
It's probably worth mentioning that there's also a closet in the room--which for now I'm not using as an equipment closet, just general household storage--that will have to be stepped, too, though it will get less frequent use.
It's so helpful to have this forum to talk this stuff through. I didn't say it at the Thanksgiving table yesterday, but I'm thankful for you guys!