ceiling/floor joist with rc channel

My studio room is currently under construction. It is a basement room with 10" floor joist above for the ceiling. I just installed r-30 fiberglass insulation (10" thick made for 10" joist) in all the floor joist. I have rc channel for the ceiling that I will install. I was thinking of a layer of 5/8" sheet roack and a layer of 1/2" sheet roack. Is this the best for the ceiling. I have read to glue the 1/2" to the 5/8" rather than screw. This makes me a little nervous for some reason. Can you just use "Liquid Nails" or is there a differnt addhesive to use. Will it hold up? Once I install the rc channel should I pull the insulation down a little bit so when the sheet rock is installed the insulation touches the sheet rock. Thanks alot. I have learned alot from this form.

Welcome to the forum, J Wah! I, like you, am more of an advice seeker than an advice giver here. However, you might take note of this:

. . . as soon as you add Resilient Channel, double frames, staggered stud frames, or even light gauge steel studs to a wall the flanking caused by fasteners becomes much less a problem, almost to the point of non-existence. . . (Full Thread)

That may be your answer. If not, or if you would like more information, just post back, and I'm sure one of the "real" experts can chime in. :) Good luck with your project... --Keith (not an expert, but I sometimes play one here) :wink:

Gluing isn't a good plan for ceilings, and in most cases not even for walls - it's been found that as long as one side of a wall's cladding is resiliently mounted (or on a separate frame) that flanking from fasteners makes little difference; and insulation soaks up whatever might make it through. I'd just go with both layers 5/8 - it seems the extra mass helps more than the slight improvement in coincidence frequency caused by dissimilar thicknesses of wallboard; hope that helps... Steve

Ignoring soundproofing for a moment, some people say that glue is much much better today than it used to be structurally, but I know of at least one ceiling that was glued up (no nails, no screws) -- in this case the gypsum/drywall was glued to the joists -- and it fell down about 7 years later, wrecking a home office and home computer.

knightfly wrote:

... - it's been found that as long as one side of a wall's cladding is resiliently mounted (or on a separate frame) that flanking from fasteners makes little difference; and insulation soaks up whatever might make it through.

Here is where my inexperience comes through...could you define flanking? I am assuming vibration or sound transmition through the ceiling. If glue is not used on the second layer of sheet rock, would you use longer screws and screw it to the rc channel? Thanks.

J Wah wrote:

...could you define flanking?

Flanking is the transfer of sound energy to structural components via firm connections, like fasteners or brackets. Think of the "two cans and string" experiment -- the sound flanks along the string. You are using resilient channel for decoupling, which eliminates flanking. I'm sure I won't win any contests with that definition, but I think it gets the point across. :wink: Edit: Here's a better and more official definition:

Custom Audio Designs wrote:

Flanking sound transmission occurs when the sound takes a secondary route instead of the direct noise path. Flanking transmission can be either airborne or structure borne. (Source)

So, there you go... Not just structural paths, but airborne paths as well.

It does get the point across. Thanks. Anyone have any thoughts on screwing the second layer of sheet rock to the rc channel with longer screws?

J Wah wrote:

Anyone have any thoughts on screwing the second layer of sheet rock to the rc channel with longer screws?

I think this has been asked and answered. :)

Awesome. Thanks.

And thanks Keith; dang, boy, sounds like you've been getting even less sleep than I have lately - is there anything here you HAVEN'T read yet? :lol:

knightfly wrote:

...dang, boy, sounds like you've been getting even less sleep than I have lately - is there anything here you HAVEN'T read yet? :lol:

Yes -- the rest of the fifteen freakin' posts you just lobbed onto this thing so far! Just keep reading... Just keep reading... Just keep reading... (Think "Dory" on "Finding Nemo...") Just keep reading... Just keep reading... ;)

I'm sorta like a tomato - eventually I "ketchup"... (covering head and running from thrown objects, INCLUDING tomatoes... :mrgreen: :mrgreen: :mrgreen: :arrow: :arrow: :arrow: