Ceiling Advice Needed

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Todzilla

Todzilla

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Friends,

Studio builder informed me that he won't finish ceiling. That is my responsibility (what can I expect for $10K?). Walls are filled concrete, floor is well supported ply on joists on overengineered footings.

Ceiling is just the exposed 2X6 joists with plywood sheathing on top. This will clearly leave the ceiling as the weak link in soundproofing.

What are some effective and cheap ways to sound proof the ceiling? I assume it would be ideal to have a ceiling that is essentially decoupled from the roof, although this may be structurally challenging.

Any thoughts would be helpful.

Thanks,
 
What's a fella gotta do to get some help here?

Do I have to stop acting like an asshole? Well, that won't be easy, but if that's what it takes, I'll muster the energy.

Seriously, any help on ceiling construction would be helpful...
 
Todzilla,

I'm assuming that the roof unfinished ceiling you are dealing with is a sloped (gable end) roof? So you basically have a structure similar to a standard garage right now?

Velvet Elvis
 
Tod,
Is it possible to post a photo of the roof structure as it is. I can think of a couple of acceptable ideas BUT I would prefer to know what is there before I stick my neck out with suggestions:D .

ChrisO :cool:
 
Thanks Mates,

Here's the side view. Yes, it is a standard gable end roof, with Cinderblocks and bricks making up all the walls. The roof (and floor) are the only wood-framed aspects of the building. I suppose building code will compell me to put at least a shallow ventilation channel between the plywood roof and the insulation that I'll put in before the sheetrock (or whatever it is I put up).

But, does anyone have experience with treating a ceiling as a weak link? I've used resilient channeling before, but never on a nearly upsidedown surface.

Anyway, all thoughts are welcomed.

Cheers,
 

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Are you wanting to keep the high ceiling? If so, I you could nail plywood or MDF to the ceiling joists, then do a resilient channel and two layers of different thickness drywall from there... the weak spot would be the seams at the top and sides.

Velvet Elvis
 
Velvet,

Yes, I very much want to keep high ceilings. So your suggestion is to put ventilation channels, stuff some insulation and then go with MDF, resilient channeling, a layer of 1/2" sheetrock and finally a layer of 5/8" sheetrock?

Since resilient channeling supports weight rather than studs, would that be a lot for RC to hold?

Thanks
 
Todzilla,

Yeah that might be alot for it to hold up... but the auralex people seem to claim it can be used to hold two sheets of drywall on a ceiling.

I would not "stuff" the void full of insulation... just a couple of layers of something with both a good R value and a good sound barrier level. Stuffing it full will actually negate both the insulation and some of the sound deadening... having a little air space would be better.

Perhaps you could do Plywood, sheetrock, channel, sheetrock.

That would save some of the stress on the channel and still give you some mass.

Velvet Elvis
 
I think Velvet has covered most of what I was going to say....lol. My only concern would be that you don't overload the joists to the point that they sag, as you are going to add some serious weight to the roof structure.

Out of curiousity, what is the outer roofing material........youknow, the part the sun shines on:D

ChrisO :cool:
 
Chris O...
Good point on the overloading the structure altogether...

It would be hard to cross brace the roof line as well since you want the gable to remain vaulted on the inside.... hmmmm...

At one of the rooms I've worked in, they wound up putting a wooden support beam from the floor to the ceiling in the center of the room... to help offload some of the weight of an otherwise unsupported roof. It looks cool and works well, but divides the "open room" a little.

Velvet Elvis
 
If I understand this correctly, you are concerned about the weight of the ceiling causing the rafters to blow out just above the wall or bow in the center. Some of that stress can be taken up by a few rafter ties and simply making the ceiling not come to a pointy peak... see drawing. Another approach might be to put up false rafters that come to a peak below the outside rafters. This would proably be the best sound proofing method and should be really secure because they are resting on the concrete block walls. Both of these should also help any ventilation issues.

Check with an civil engineer too :)

Kevin.
 

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Civil engineer check:

The false rafter design looks a bit hairy. You will be adding outward forces to the top of the walls, which may cause them to break...
false_rafters.gif


Youa would need to add rather low rafter ties to keep the walls together:
false_rafters_with_ties.gif


BTW, are the walls of different height?

/Ola
 
Ola asks:
BTW, are the walls of different height?
Click to expand...

Todzillas drawing was much better then mine... it had equal height walls.

Kevin.
 
Wow! Great input, although I owe y'all answers to a bunch of questions.

1) walls are identical in height

2) There are rafter ties already in place, but they are way up high, only about 5 feet wide, less than 2 feet from apex.

3) Roofing is standard tarpaper with 30 yr. shangles on top of that.

4) There is a wooden support beam from the floor to the apex, but is is not centered from front to back. It is about 7 feet from the back wall, so about 14 feet from front wall. (It holds up the spousal doghouse sleeping loft). So there's some central support, but it still leaves a 14 foot span.

5) Builder is a conscientious builder and musician. I can discuss the load bearing capacity with him.

6) The suggestions given are really only adding one or two layers to what would normally be on the ceiling. I.e., an extra layer of sheetrock and/or plywood.

7) I believe every joist is connect to the walls via hurricane straps, which is appropriate for this part of the US

Anyway, keep the suggestions coming, I am getting great ideas from this dialog!

Regards,
 
Velvet Elvis said:
I would not "stuff" the void full of insulation... just a couple of layers of something with both a good R value and a good sound barrier level. Stuffing it full will actually negate both the insulation and some of the sound deadening... having a little air space would be better.
Click to expand...
Are you sure? Maybe you're right but I would guess that e.g. rockwool would help the soundproofing. I would have guessed that some rockwool attachet to the plywood would help stopping e.g. sound from rain. Then some air and finally the layers of sheetrock.

Keep in mind that the best soundproofing is "airtight seal" but you do not want to create an airtight seal, with no ventilation around your joists. Make the layers closest to your room airtight but allow for ventilation in the rest of the structure. Never ever create two airtight layers in a wall or a roof structure. Uless you like mold and rotting wood...

Todzilla, what's the climate like where you live? I read "hurricane straps" and feel that I'm not qualified to give you structual advise. The weather I have worry about when calculating roof structures is snow. Yes this would hold up but what if you add six feet of wet snow to it..." We make thick roofs over here :)
 
Ola,

Yes, ventilation will be critical, so seals will have to be made that still allow sub-roof ventilation.

As for weather, I live in the piedmont area of North Carolina in the US (think of the midway point between Washington, DC and Atlanta). The winters are rarely snowy or icy, although two winters ago, we had record breaking 60 cm snowfall. The summers are hot and humid, with temperatures sometimes hitting 40 degrees centigrade.

Wet rot will certainly occur if ventilation is not properly performed. I want good soundproofing, but I don't think I want rotten roof joists falling on my head while cutting tracks 8^).

Thanks for the advice,
 
Ola,

By "stuff" I mean over filling the cavity. Insulation loses its ability to insulate if you put too much into a cavity. I seem to recall reading the same about its acoustical properties. You can FILL the void (leave your ventilation channel in though!), but do not STUFF the void. Am I making sense?

Velvet Elvis
 
Velvet,

You mean fill it, but don't cram it, right?

ENclosed is a gif that shows my latest thought on how I might approach this. The only question is whether or not I can get away with the resilient channel straight from the joists with no intervening sheetrock. It seems like the remaining sheet rock will have a big job to maintain airtightness.

Any thoughts?
 

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Todzilla,

Yes... fill it (with the exception of the vent path) but do not cram it in.

Looking at your drawing, I would think a wiser move might be to cover your rafter system with plywood and seal that well prior to doing the resilient channels and the drywall... So you would be able to seal up the room using the plywood with the rockwool/insulation above it... then put the resilient channels in with your two layers of drywall.

Velvet
 
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