Yet another detached garage practice room thread

Hi all. Technically, this is my 2nd "I'm building a practice room" thread but since the first one was so long ago now (and I don't think I had all my ducks in a row then), I thought I'd start a new one. I've also included pictures. (Damn sketchup for not having a linux version.......) Anyway, I would like to contain a healthy amount of volume here (say, 100-115 db) and plan on doing a room within a room and think I've stumbled upon a decent way to accomplish this but wanted to get some outside opinions. My neighborhood at its most quiet is about 45-50 db and my closest (and most friendly neighbor) is about 30' away. My most unfriendly neighbor (and I'm being kind here) is about 50' away. The main question I have is what to do about a single support post that is connected to my first room (the 'container-room' or 'first room', I suppose). I'm most worried about flanking but perhaps there's something I could do to minimize it? Here's my first drawing .....and a cross section of the room with a rough plan for the support beam (i.e. layer drywall on top of all sides even though the picture shows only drywall on 2 sides. You know what I mean though.) --Note: The area above (where the plywood is) would be used for storage. (EDIT: This wicked drawing was fixed in the post below. El-Linko: viewtopic.php?p=98316#p98316) So a couple of questions then..... How much weight are joist hangers able to handle? According to this post about drywall weight, if I were to do 2 layers of 5/8" drywall on a room that's roughly 19' x 18', those joists would be holding approximately 2072 lbs! How much transmission loss would 2" between leaves give me as opposed to 1"? Technically, I could come in on the sides (wall-wise) as much as I want but the area between ceiling leaves is not as flexible as I'd like to have a decent amount of headroom. In regards to that support post in the middle of the room, could I reduce flanking with neoprene between the contact point of the 'main beam' and said support post? Is there a post material that is less "flank-y" than others (i.e. metal vs wood?) Perhaps neoprene where it meets the floor? I can't be the only one who's ever dealt with this. I welcome any thoughts. Thanks.

[tumbleweed blows across the screen......] [brisk wind blows through thread......] bump?

A couple of thoughts: The top sketch (just the framing) looks to be workable to me, but then the bottom one (with drywall) doesn't. In the lower sketch, it looks like you have the drywall attached directly to the support studs for the "main beam", which kind of defeats the whole purpose of the exercise since that beam is your outer-leaf, and the drywall is supposed to be your inner-leaf. It would be much better to attache that drywall to the inner-leaf framing that you show in the upper sketch.

How much weight are joist hangers able to handle? According to this post about drywall weight, if I were to do 2 layers of 5/8" drywall on a room that's roughly 19' x 18', those joists would be holding approximately 2072 lbs!

That is a question that you most likely wont get answered here. You should hire a structural engineer to visit you, check the existing construction, look at your plans for what you want to do, and give you professional advice on what you need in order to accomplish it, in terms of local code, materials, safety, construction techniques etc. Yes, there will be an awful lot of mass up there above your head, and yes it does need to be supported correctly.

How much transmission loss would 2" between leaves give me as opposed to 1"?

Minimum recommended air gap is 4 inches. Better is 6" or even 8", if you can afford the space. A wider air gap improves transmission loss greatly, since it lowers the resonant frequency of the MSM system. But don't get confused: The gap refers to the space between the SURFACES of your leaves, not the FRAMING of the leaves. So, for example, if you have a concrete outer-leaf wall, then a 1" gap, then a 2x4 stud frame with drywall on it, well your air gap is nearly 5" in that case: the 1" gap, plus the depth of the studs. (Unless, of course, you build that wall "inside-out" in which case the gap would actually be less than 1"!)

In regards to that post in the middle of the room, could I reduce flanking with neoprene between the contact point of the 'main beam' and said support post? Is there a post material that is less "flank-y" than others (i.e. metal vs wood?) Perhaps neoprene where it meets the floor?

It won't help much at all, since you will still have to nail/bolt/screw the beam to the posts and to the floor somehow. The nails(bolts/screws create a flanking path of their own that bypasses the neoprene. In any event, since that is all part of your outer leaf, it doesn't really matter if it flanks to the rest of the outer leaf or not. What DOES matter is keeping your outer-leaf entirely decoupled from the inner-leaf: no mechanical connections AT ALL. Not even one little nail. Right now, from your lower sketch, you are not doing that. That drywall needs to go in the inner-leaf framing, not the outer-leaf framing. - Stuart -

In reference to you joist hanger question, is it safe to assume you have Simpson hangers? If this is true it would be easier for you to contact them directly with your question about load, they can be contacted through the corporate website found at : http://www.strongtie.com These hangers are designed to meet and even exceed codes that apply. When properly installed, hangers replace a typical ledger/joist connection. But there can be outside influences that may require additional shear brackets. Certain requirements for live load may influence the distribution of these in a typical layout. Contact the hanger makers directly with your questions.

Stuart and xspace thanks for the replies. This is precisely what I was looking for. Unfortunately, I don't think my 2nd drawing is correct. I'll take some time this wknd to tweek it a bit and repost it. Again, though, many thanks.

Ok... Stuart, I've changed things to show that technically the drywall around the post will not come into contact with anything in the outer room. And....I've drawn another picture. This is a top-view of the support post which is connected to the 'main beam' of the outer room (and the floor of the main room, obviously). One thing I'm thinking, however, is of cutting a 1/4" gap between the slab of the main room and then pouring a new footing for this post to reduce flanking from the slab up the post and then into the main beam which is connected to everything in the attic of this garage. Any thoughts? I actually just spent a good hour combing through the Sharward thread (again!!) today. Quite a story..... Thanks guys.

"In regards to that post in the middle of the room, could I reduce flanking with neoprene between the contact point of the 'main beam' and said support post? Is there a post material that is less "flank-y" than others (i.e. metal vs wood?) Perhaps neoprene where it meets the floor? I can't be the only one who's ever dealt with this." The problem with a post that is carrying a load, like this one, is that it links the flanking overhead where it connects, directly to your floor. Sealing around it doesn't remove the effect it has as far as flanking into your floor. This is a critical part of your >existing< room, this post. It is supporting an overhead load and it is a difficult feat to remove/move or even support the overhead load while you attempt to demo the existing concrete and build a new/deeper footing for the post. Cutting the slab around the perimeter of the post as you are thinking to do, might only be a short term solution. As it is right now, the full slab is aiding in the distribution of the weight loaded on the post. Any change that is made to this connection will reduce the ability of the concrete to support the overhead load. It may settle immediately and cause a shift in the overhead load that could prove fatal. So you have a post that may dictate that either the post will simply remain or you will require much more attention to what is going on with this load and how can you properly and >safely< either remove it completely or rehab the footer in such a way that this load will remain unchanged.

Thanks, xspace. OK.....I should've added that this post does not yet exist. In fact, the main beam is currently only supported at both ends and NOT in the middle. The addition of this middle support beam is simply for additional peace of mind after I found out how much weight the structure will actually be supporting. If this were an actual support post that was currently being used, I would (most likely) not be messing with it at all. What I'd like to do, obviously, is limit the incidence of flanking from the floor to the main beam after it's been added in. Sorry for not being more clear from the get-go but your concern is appreciated. Thanks again.

OK.....so here's something I've been wondering about: My garage sits on an old exposed footing (i.e. the footing protrudes beyond the walls. For the record, I've flashed the whole thing so that water does not touch this footing.) Now...because the first leaf (the outer wall) sits on the same floor as the inner wall, would my proposed idea of cutting out the existing concrete and pouring an isolated footing for the additional support post be for naught? After all, if flanking from the floor is going to happen, wouldn't it be flanking to the outer leaf anyway? Since both leaves sit on it? Or perhaps giving the additional support post its own footing would reduce flanking by a bit? (Kind of like being "less pregnant"? :lol: ) It almost seems like flanking is flanking, right? Maybe this picture will illustrate my point a bit more: However, with all of that being said, the footing that the outer leaf sits on is the original "old" footing. A new slab was poured (before I moved in) that the inner leaf will be sitting on. These do touch though so it isn't like there's any "real" isolation going on but I'd imagine that there's some reduction in flanking simply due to the differing pours. Anyway.......any thoughts? Thanks, as always.

Alright, I've read enough posts on here to realize when someone could be more clear in their description of their respective issue(s). Am I not being descriptive enough? Unclear somehow? Just lemme know. Thanks.

Pure L wrote:

OK.....so here's something I've been wondering about: My garage sits on an old exposed footing (i.e. the footing protrudes beyond the walls. For the record, I've flashed the whole thing so that water does not touch this footing.)

External image, not preserved — original: http://i204.photobucket.com/albums/bb78/Pure_L/outside-view1.gif

Now...because the first leaf (the outer wall) sits on the same floor as the inner wall, would my proposed idea of cutting out the existing concrete and pouring an isolated footing for the additional support post be for naught? After all, if flanking from the floor is going to happen, wouldn't it be flanking to the outer leaf anyway? Since both leaves sit on it? Or perhaps giving the additional support post its own footing would reduce flanking by a bit? (Kind of like being "less pregnant"? :lol: ) It almost seems like flanking is flanking, right? Maybe this picture will illustrate my point a bit more:

External image, not preserved — original: http://i204.photobucket.com/albums/bb78/Pure_L/walls-top-view1.gif

However, with all of that being said, the footing that the outer leaf sits on is the original "old" footing. A new slab was poured (before I moved in) that the inner leaf will be sitting on. These do touch though so it isn't like there's any "real" isolation going on but I'd imagine that there's some reduction in flanking simply due to the differing pours. Anyway.......any thoughts? Thanks, as always.

You local building contractor might say: If you can open up a 36 inch hole (squared) at least 24 inches deep, then you can pour a block footing to put a support post on. The Contractor would know with some absolute what load the post would be maintaining...this is a critical evaluation. As to the slabs that are actually touching...it is what it is :) Sure there may be a frequency that gets lost in the flanking but with the weight, the mass the direct contact, don't expect to identify which one it is:)

Stuart, xspace.... I edited the picture from above. My pictures blow....... I'm workin' on it! But this would essentially be giving me one additional flanking path, correct? (i.e. As opposed to only the walls being on the same floor/slab, I've now got the walls plus this beam?) Is flank-factor cumulative like this?

That looks like it should work. I think! A SketchUp model would be better... .)

Soundman2020 wrote:

That looks like it should work. I think! A SketchUp model would be better... .)

Consider that gauntlet thrown, Stu!

Hi all. I'm putting some plywood on my door. In fact, it is very close to looking like this (1st seal is done, anyway!) One thing I'm wondering about...... Is there any product (Green Glue or something similar......I'm fully aware that it might not exist) that I should spread to fill any small voids where the plywood is not 100%, perfectly flat against the door? I plan on screwing it to the door, obviously, but if there's something that could be spread between the plywood and the door for extra "sauce", I'd be happy to hear of it. Thanks.

Bondo :)