Adding sheetrock to an existing ceiling

[Phyl]

The ceiling in my live room is one layer of sheetrock that has been textured. I'm going to add one more layer of sheetrock.

Do I need to use mud before adding the second layer of rock, or will it not matter?

 

[RICK FITZPATRICK]

Hmmm, how has the existing layer been textured if the joints arn't mudded? Unless you are talking about LEVELING the texture. That might be impossible to level completely, although it may be worth a try if the texturing is relativly flat. If it's POPCORN, simply spray water and scrape it off. Messy though. I've done it. If its ORANGEPEEL, it'll take a ton of mud. If its KNOCKDOWN, hmmm, like I said, it depends on how rough. You might sand it first though to knock down any peaks. The point here is to not allow an air gap between layers. But considering other factors, such as flanking through ductwork, I don't know how much improvement you will get anyway. Maximum improvement by doubling mass is 6db in transmission loss, but many factors will lower this. Even as much as.......NO IMPROVEMENT. Structural transmission via the walls, etc. If it were me PHYL, and the rooms weren't very big, I'd consider REMOVING the existing drywall ceiling and adding layers between joists, and then use RC perpendicular to the joists to hang another 2 layers like we said before. But only you know the WHOLE ball of wax here. I think you said you have pipes BELOW the joists, correct? Where are they in relationship to the existing drywall? I think you need to tell us the whole scenario before commiting to another layer. It may add very little LOSS under some circumstances.

Question though. Don't you have ductwork that is common to the lower rooms and upper floor?
fitZ

 

[Phyl]

Don't you have ductwork that is common to the lower rooms and upper floor?
fitZ

I do, and they are already covered by sheetrock.

 

[RICK FITZPATRICK]

I do, and they are already covered by sheetrock.

Then whats the point of adding drywall if FLANKING can occur through the ducts? IF these ducts are COMMON to both the lower and upper floors, then sound flanks through the grills and up into the upper rooms.
fitZ

 

[Phyl]

Admittedly I'm making a lot of compromises, but am trying to do so without wasting time and money.

The ducting we're talking about is common to both the control room and live room (downstairs) and the upstairs. I've closed off the ducts in the live room and plan to use fans when necessary to move air in and out of this room. The ducting will be covered by two layers of sheetrock, this is my attempt to minimize the amount of sound that makes its way from the live room to the control room and upstairs rooms.

I've attached a drawing to clear things up.

 

[RICK FITZPATRICK]

As usual with home recording, compromise is the name of the game. I am no exception. In fact, I'm not wasting anything on isolation as my stuido is on a second floor. There is NO improving my floor considering how its built, where I am located, what I am recording and who will hear it. Mine is PURELY for my own pleasure and experience, so treatment is my only real option. Good luck Phyll, and by all means have fun. Oh, yea...go ahead with the drywall. Let us know how much it improved the isolation. Which is subjective without tests, but if you hear a difference, and its satisfactory to you, what the hell, great!!
fitZ

 

[jpw23]

Admittedly I'm making a lot of compromises, but am trying to do so without wasting time and money.

The ducting we're talking about is common to both the control room and live room (downstairs) and the upstairs. I've closed off the ducts in the live room and plan to use fans when necessary to move air in and out of this room. The ducting will be covered by two layers of sheetrock, this is my attempt to minimize the amount of sound that makes its way from the live room to the control room and upstairs rooms.

I've attached a drawing to clear things up.

I can see a few problems with shutting off the vents in the live room.....this is not sound related.......your hvac system was designed to move a given amount of air(110 cfm through a 4x10x6 run) 400 cfm per ton of cooling, a 3 ton system would need to move 1200 cfm to operate properly.....when you go shutting down vents.....you comprimise the efficiancy of the system and with enough vents shut down you could damage the system, like having freeze-ups, liquid refrigerant making its way back to the compressor which will blow the valves out of it or wash the oil from the crankcase and burn up the compressor. Also....shutting down vents will cause noise in other rooms of the house ......that air has to go somewhere! I would suggest leaving your hvac intact and do what I do......when I record a vocal track.....I turn it off!.....BTW.....I am an hvac service tech(25 years)

 

[Phyl]

As usual with home recording, compromise is the name of the game. I am no exception. In fact, I'm not wasting anything on isolation as my stuido is on a second floor. There is NO improving my floor considering how its built, where I am located, what I am recording and who will hear it. Mine is PURELY for my own pleasure and experience, so treatment is my only real option. Good luck Phyll, and by all means have fun. Oh, yea...go ahead with the drywall. Let us know how much it improved the isolation. Which is subjective without tests, but if you hear a difference, and its satisfactory to you, what the hell, great!!
fitZ

Thanks Rick, I always appreciate your perspective on things.

I'll start thinking about some sort of before and after test to evaluate how much better things are after the remodel.

 

[RICK FITZPATRICK]

Thanks for the tips JPW23. No one can know everything about this studio stuff, especially HR people. Thats why this bbs is such a great resource. I'll remember your tip.
fitZ