Post subject: Help with contractor deviating from the plan

[hoanghuynh]

Hi all. I am building a single room for live recording and mixing in my basement and the contractor just finished the framing. Room is 23'3" long by 13'1" wide by 7' tall aprox 500 sq ft. Two walls are a single frame on concrete, two walls are double framed so not to attach to the rest of the basement. All the walls are floating on a concrete pad. Floor is going to be finishing the concrete that's there (open to other ideas). All walls will have RC Channels and R40 insulation, double sheet rock with green glue. My concern is the ceiling and where the walls hit the floor. the ceiling will have RC Channels, double sheet rock with green glue but It was supposed to be separated from the house like the other two walls. They have nailed the frame to the upstairs floor and it is touching the beams. There is duct work and pipes running above the room. To mitigate the lack of "room inside a room" the contractor wants to put a layer of expanding foam and then R40 insulation. I am still concerned that even with the RC Channels, double sheet rock, green glue etc. this will not prevent bass and sound traveling up through the floor and into the living room. My drums can hit about 115db when playing hard. I will have acoustic treatment and bass traps in the corners. Where the the walls hit the floor there is going to be a gap that he plans on filling with R40 and an acoustic caulk.
Is the ceiling in bad shape and what can be done about where the walls touch the floor?
Thanks~

[Soundman2020]

Hi. Please read the forum rules for posting (click here). You seem to be missing a couple of things!

That said, it looks like you are in a complicated situation. Rather similar to what happened to another forum member in Greece a few years ago. You might want to take the time to read about that: http://www.johnlsayers.com/phpBB2/viewt ... =2&t=17363

OK, so first of all, how much isolation do you need, in decibels? That's the basis for determining how to build your isolation system, what materials to use, and what techniques to use. You say 115 dBC loud: Fine! But how quite does that need to be on the other side? That's the key...

Two walls are a single frame on concrete,

Do you mean that the frame is physically attached to the concrete? Or is it that you have a concrete wall, then a gap, then framing?

two walls are double framed so not to attach to the rest of the basement.

Something doesn't make sense here: If those two walls are not attached to the rest of the basement, but the other two are attached to concrete walls, then how are they decoupled? Please post some photos of what you have, and an accurate diagram.

All the walls are floating on a concrete pad.

Do you mean that you have a proper floating floor concrete slab there? Raised on isolation mounts, and with an insulation-filled air gap between that slab and the underlying base slab? If not, then in what way is your "concrete pad floated"?

Floor is going to be finishing the concrete that's there

Excellent! Nothing better. If you don't like the look or feel of bare concrete, another option is to lay thick laminate flooring directly on top of it (with a suitable underlay, of course).

All walls will have RC Channels

If your inner-leaf framing is already decoupled, then you do not need RC! If it is decoupled once, then it is decoupled.... there's little point in decoupling a second time. However, if your inner-leaf framing is NOT decoupled, then you DO need RC (either that, or RSIC clips plus normal hat channel).

the ceiling will have RC Channels, double sheet rock with green glue but It was supposed to be separated from the house like the other two walls.

Once again, if your ceiling framing is already decoupled (due to being supported ONLY on the inner-leaf wall framing, which itself is fully decoupled...) then you would not need RC. But since the contractor screwed up and attached the ceiling framing to the joists above, you DO need RC here. However, this will NOT give you as much isolation as having a properly decoupled frame. RC is good to a certain extent, but not as good as decoupled framing. Depending on how much isolation you need, RC might not be enough.

They have nailed the frame to the upstairs floor and it is touching the beams.

If they were clearly instructed to NOT do that, and you have it in writing, then tell them to rip it all out and re-do it, at their expense, not yours. If they did not follow the plans or written instructions, then they screwed up, so it is their responsibility to fix it. Of course, that also assumes that the plans and instructions meet code, passed inspection, and were duly approved by your local authorities...

There is duct work and pipes running above the room.

That should have been dealt with BEFORE putting the ceiling framing up! How will you be able to isolate that now? Answer: you can't. That duct is a direct and massive flanking path for sound into the rest of the house. If you do want isolation, that WILL need to be fixed. So your ceiling framing has to come out anyway, either at the contractor's expense, or at your expense. If you don't fix that duct problem, then you are limited to about 33 dB of isolation, no matter what else you do, with or without RC, clips, Green Glue.

To mitigate the lack of "room inside a room" the contractor wants to put a layer of expanding foam

Most types of common expanding foam is acoustically useless. If it is typical closed-cell "foam in a can" or closed-cell polyurethane spray foam, then there's no benefit to that at all, acoustically. It might seal the gaps, which is good, but that's about it. And it most certainly will NOT compensate in any way for the major screw-up where they nailed the inner-leaf ceiling to the outer-leaf! Nothing can compensate for that, except for proper decoupling.

and then R40 insulation.

What type? R40 is a thermal value, not an acoustic value. You can get R40 in fiberglass insulation, mineral wool, cellulose, polyester.... and all of them would have vastly different acoustic properties. Use only mineral wool (in which case the density must be around 50 kg/3, roughly 3 PCF), or fiberglass insulation (in which case the density mist be around 30 kg/m3, roughly 2 PCF). And it must fill the entire cavity, top to bottom, surface to surface, but without being compressed.

I am still concerned that even with the RC Channels, double sheet rock, green glue etc. this will not prevent bass and sound traveling up through the floor and into the living room.

Your concern is valid, and you are correct: that won't isolate a drum kit. Kick, snare and toms will be heard upstairs.

I will have acoustic treatment and bass traps in the corners.

That helps the room to sound better inside, but does nothing at all for isolation. It makes no difference for that.

Where the the walls hit the floor there is going to be a gap

Huh? How can there be a gap??? The walls must rest ON the floor, and be firmly attached to it! How can they support anything if there's a gap under them? Are they hanging from the ceiling???? The wall framing must sit directly on the concrete, and be correctly attached to the concrete with anchor bolts or tap-cons. No gaps! Please post some photos of that, so we can see what is going on here. This is VERY strange...

Is the ceiling in bad shape ...?

Yes the ceiling is in bad shape, and needs to be take out and fixed. That will also allow you to fix the issue with the HVAC ducts, which is a major problem. The pipes might also be a problem, but to a lesser extent.

... and what can be done about where the walls touch the floor

I am not understanding at all how thye managed to build walls that hover above the floor: I very much doubt that would pass inspection, even if I could figure out how he managed to do it! Sole plates sit on the concrete, and are bolted or tap-conned into it. The studs sit on the sole plate, and are nailed into it. the top plates (double) sit on top of the studs and are nailed into them. The framing does not touch anything else, but it MUST sit on the floor, since that's what supports it, structurally. The sheathing is attached one layer at a time, resting each layer on shims to keep a slight separation from the floor, so that it can be correctly sealed later with backer rod and caulk. That's it! That's how walls are built, always. I have no idea how he could build a wall that does not rest on the floor....

- Stuart -

- Stuart -