Exposed ceiling joists and Acoustical Issues?

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I am converting a garage apartment into a studio. The apartment as configured has a steeply pitched roof but only a seven foot ceiling. The ceiling joists tie together part of the roof beams and two small shed roof which were put in to provide floor space.

I have no idea whether the removal of the ceiling joists will have structural implcations, but I have no desire to have several tons of 2x8s and slate tiles come down on my head, either. Therefore, I am going to leave them be and push the ceiling up to a height of 9 feet for better acoustics.

So my question is: Will leaving these ceiling joists (2x4s, 16 inches on center, around 10 feet long) have any acoustical impact? They certainly will give me something to work with on track lighting, since I can mount lights directly on them using wire mold, and will be able to position lights up and down, depending on how I want to light the room. I can also hang microphones from them.

Any thoughts?
 
Eminant collapse?

Hi, are the joists perpendicular, or parrallel with the monitors? I doubt if they will have a serious impact, although I'm no expert. However, someone here probably can give the real scoop, as ANYTHING that is solid, and takes up space, impacts sound by either reflection or absorbsion. They might resonate at a certain frequency, and the wood itself will absorb, how much is probably miniscule. However reflection is another aspect, as a sound wave hitting anything will be reflected to some degree. It is this "some degree" that I am not qualified to say anything about. And since you have no way of telling the difference between them being there or not right now, raising them seems a little drastic. Especially if they are still going to be exposed IF I understand your description, these are ceiling joists, not roof rafters, is that correct. If so, you can see the underside of the roof, correct. If that is the case,if you ARE planing on removing these, and you have a slate roof. Do not. If I'm seeing this correctly, these are "ties", which "are" the ceiling joists. They keep the walls from pushing out from the roof load, which pushes down. If it can not push the walls out , it can not push down. Therefore, no collapse. They are there for a reason other than nailing sheetrock to. And that is structural. Hope this helps. At least, thats my 2cents
fitz:)
 
If I picture your garage apartment correctly, you have ceiling beams that are parallel to the floor, with a peaked roof above that. If thats correct, here are a few suggestions.

1. The Spacial

Since recording studios generally sound better with more air available, one option is to sheet rock the inside of the eaves (roof) after insulating, then paint the horizontal beams a contrasting color or the same color, depending on your preferences. While your beams will still be in the same place, you'll have lots of air above that add to the overall volume of the room, which will add for nice sound, and a more open feeling, especially if there is a skylight or two up there and/or painted bright white or yellow.

2. Beam reduction

Another option is to double up every other beam, then cut out the middle beams. What you do is buy additional 2x8's, using 1/2" carriage bolts is cover both sides of an existing ceiling beam with the new 2x8's, bolt it all together, then repeat every other beam. Once finished doubling every other beam, cut out the beams in between. You will now have 32" between the beam centerlines, and not reduced the structural integrity more than a few %. You can put a ceiling on the top of the beams, or do the "spacial" above.

3. Beam relocation.

This is my favorite option, actually. For every horizontal ceiling beam you have, buy two more of the same size and thickness (2x8, 2x10, etc). Mount new pairs of beams as above with carriage bolts, however mount the new beams 1/3 or 1/2 the way up the slanted joists (roofline). By doubling the joists, you're adding strength, allowing you to cut out the existing joists. Personally, I would leave the end joists 16" off the wall, and sheet rock the ceiling from the wall to the first joists on either side, then vertically up to the new joists. Or, you could leave it open as in #1 if you like. Either way, you have more volume in the room and not sacrificed structure enough to cause the place to come crashing down on you.

A structural engineer could confirm my above suggestions, but all three work out very well for studios. The last one is my favorite, if I haven't mentioned that already. You end up with a nice 16" ceiling perimeter at the existing joist height, then a big square/rectangular raised ceiling above that. Some nice halogen track lighting way up there aiming down would be nice, and you wouldn't have the heat of the bulbs blasting on your head.
 
Truss's?

Hi, something just occured to me. If these are indeed ceiling joists, and they are 2x4, and they tie the 2 opposite walls togeather, can you see the peak of the roof at somewhere approx. plumb to the middle of the room? What did you say the span of the room is(or of these joists?) I've seen large spans with 2 x 4 bottom chord construction, but they were part of a roof "truss". These are usually found in newer construction, as they are easy to constuct at a mill, and then delivered to the jobsite. They are engineerd to carry the load such as slate. These usually have metal sheer plates nailed
at all joints. They work by distributing the load to specific points. These are not easily modified, and should you indeed have these, frederic said the magic word. Engineer.
I am not an expert in this field, just trying to help the design floiw happen:D However, this may NOT be the case, you may have custom truss's built by the homebuilder, or even, homeowner and or carpenter standard contruction. In either case, you have a slate roof. And I don't mean to be condencending, but slate is heavy. As frederic suggests, I would get a professional opinion on this one as far as how high to raise the "tie" if you canBut frederic is right on if its standard construction and a lightweight roof. Ok, thats my second 2 cents. Thats enough. Hi frederic:)

Ps, I've seen truss's where the bottom chord(your 2 x 4), is also a gable, creating a cathedral ceiling, which an engineer may be able to tell you how to do. That is another option.It also creates a larger airspace between the cieling and the roof, and, creats a cieling that is not parallel to the floor. Helps with standing waves I believe. Of course, that is if you sheet rock the bottom chord(cathedral ceiling).The pitch of the ceiling will be less than the pitch of the roof.
fitz:)
 
Thanks for the input

I was going to raise the ceiling so that it was above the existing joists anyway to give more acoustical headroom to the room. I like the idea about taking out every other joist and doubling up the remaining joists but I think I will consult an engineer before I get myself killed.
 
Hey Ob, you're back - I'm glad to see I'm not the only one that takes 10 times as long as they should to make decisions - although, in your case, considering a few tons of flat rocks on your head, time spent weighing (pun intended) your options is only a case of sanity rearing its ugly head.

If you decide to leave the ceiling height chords where they are and open, you will have reflections off the flat surface, diffraction off the corners, (bending) and some diffusion due to all the above. The extra room volume would be good as has been mentioned. If the joists cause smearing problems with your stereo image, due to early reflections, you could hang a "cloud" over the mix area and still get the advantage of greater room volume. This could be as simple as a sheet of plywood hung from the joists and covered with acoustic foam, or a framed fiberglas absorber covered with cloth.

If you decide to raise the chords, an engineer is definitely the way to go. If you go too far, you will cause the part of the rafters that is below the level of the chords to act as an un-supported rafter, which negates the truss effect and isn't a good idea even without 3 tons of flat rocks overhead.

If you go ahead, another option would be "scissor" trusses. I tried to find a link for you, but my fucking ISP has their head so far up their ass that a glass belly button would only contribute to indecent exposure...

Anyway, scissor trusses (do a google search, maybe you'll get luckier than I am) would let you improve everything. You could build them in place without compromising structural integrety, using 1/2" plywood tie plates each side of the chords, fastened with plenty of construction glue and either ring-shank nails or screws, using lots of clamps until the glue dried. I built trusses in place in a barn that I wanted the inner poles removed from, worked great. Survived a near hurricane the next winter...

The scissor truss approach would give you a vaulted ceiling, so you'd get more volume than a flat ceiling, you'd have non-parallel surfaces (good) and could put your median listening plane perpendicular to the roof peak for best acoustics. You'd have to watch and not get into the dreaded "triple leaf" scenario, which actually diminishes sound proofing. You could make sure the lower chords of the trusses are oversized enough to support 2-3 layers of sheet rock, put your insulation up at roof level, place Resilient Channel directly on the lower chords of the scissor trusses, attach the sheet rock to the RC, and tune the room with absorption as necessary.

Since you're obviously giving this project the thought it demands, I figured I probably wouldn't slow you down too much with this idea, and it might be the best way to go... Steve
 
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