Outer Leaf for my garage studio

Hi— I’ve been “lurking” on this site for a few months, now, and I’m quite grateful for all that I’ve already learned—thank you! I’m finally to the point in my own project where I could use some advice. I live in Seattle, WA, and I’m going to build a studio in my one-car garage, which I’ve enlarged as much as my property and local building codes allow. Originally, it measured 11’ by 18’ (outside dimensions). I’ve added on to the front of the building so that it now measures 11’ by 30.’ I wish I could make it wider, but that just wasn’t possible. My hopes for this space are to play with small groups of musicians (3-4, including myself) and to be able to record live drums. Ideally, I would like to have separate tracking and control rooms, but I realize that the relatively small dimensions I have to work with might make that difficult. Whatever the plan for the interior ends up being, I will definitely use double-wall construction. The floor is concrete slab on grade, and I’ve decided after reading a lot of the posts on this site that I won’t float the floor. Isolation will be quite important, though; my neighbors’ house is only about 12’ from the garage, and they have three young kids. My plan in this respect is to do as much as my budget allows, trying to get the most “bang for my buck.” If, in the end, I still feel that acoustic drums are too noisy, I’ll have to settle for electronic ones. Budget-wise, I’m doing all the work myself (used to be a carpenter), so I’m saving there, but I guess I might prefer to add another layer of drywall rather than spend a ton of money on Green Glue, for instance. The reason I’m posting this now is that I would like to complete the exterior shell of the building while I continue to learn on this site about the particulars of designing and building the interior, as well as becoming competent at Sketchup. Hopefully, once the building is roofed, sheathed, and sided, I will have a plan ready to begin the interior build-out. So, on to my question (the first of many, I’m sure): I’ve decided that I’m going to end up pulling off most of the siding on the original structure so that the finished product will look as good as possible. Given that fact, I would then have the opportunity to attach an extra layer of sheathing (exterior grade drywall) to the exterior of the entire building before doing the siding. My thought is that this would be an easy way to beef up the outer leaf. I would then add another layer of drywall inside the building, between the studs, making the outer leaf a sandwich of drywall/wood/drywall. My concern in doing this is that the original building is 100 years old, and because of that, the sheathing is a mixture of 1x4’s, 1x6’s, and 1x8’s—not the most airtight thing in the world, although there are no visible gaps between the boards. If I don’t want to caulk every single joint between every single board, am I better off beefing up the outer leaf from the inside (two or three layers of drywall between the studs)? Or should I think about adding two layers of drywall on the outside of the building, thus avoiding the hassle of fitting all that drywall between all those studs? I guess one other option would be to remove all the old sheathing and replace it with new so that I have a more consistent leaf. I should mention that the new addition has 1/2” plywood sheathing on the front and on the side that faces my house, but the side that faces the neighbors’ house has 5/8” exterior drywall (required by fire code because of its proximity to the property line). I suppose that if I had it to do over, I could have sheathed all the new construction with exterior drywall (which is quite expensive, by the way) but I didn’t think of that possibility until now. What I’m getting at here is there are three different types of sheathing on the garage right now: the 100-year old 1x material, the 1/2” plywood, and the 5/8” drywall. The bottom line is, I’m concerned that one layer of this leaf is made up of multiple pieces of wood that might lessen the mass I’m trying to achieve by beefing it up in the first place. I just want to be sure that whatever I do, I’m being smart and not spending a bunch of time and effort to get poor results. I can’t think of anything else to add—thank you in advance for any advice you can give me!

"I would then have the opportunity to attach an extra layer of sheathing (exterior grade drywall) to the exterior of the entire building before doing the siding. My thought is that this would be an easy way to beef up the outer leaf." If I had it to do, this would be my process as well. Adding mass directly to the outside and then adding an additional layer on the interior seems the most logical way to go. 5/8" OSB plywood is a typical structural sheathing and is most often the more economical solution vs. exterior grade sheetrock, so you may want to look into OSB if you have not already committed to the exterior sheetrock.

Thanks for the quick reply, xSpace. That gives me another option to look at. I should still probably use the exterior drywall on the side facing my neighbors (fire code) but I could do the rest in 5/8" OSB. I guess the reason I was thinking of exterior drywall over the entire outside is that I thought it would add more mass than other products like OSB. Is that not a big enough consideration considering the additional cost? Secondly, are you saying I don't need to worry about the fact that one of the layers of my outer leaf would be comprised of strips of 1x4 and 1x6 material (in the original structure)? This fact would not detract too much from the mass of the outer leaf? Or do I need to consider investing the additional time and money into tearing off that old sheathing and replacing with new OSB or plywood? Thanks!

Bigsby wrote:

I guess the reason I was thinking of exterior drywall over the entire outside is that I thought it would add more mass than other products like OSB.

REFERENCE AREA - Useful threads/links: viewtopic.php?f=2&t=2125 According to the information on the linked page [under "Weights/Densities of common materials"] sheetrock is a few pounds lighter in density then OSB plywood. But OSB is a more rigid product...so that is the trade off, but for a structural exterior application, the OSB beats the other. If you install an exterior grade plywood to the exterior of the 1X sheathing material that exists on the building and then you install sheetrock on the interior side of this same wall, you can effectively trap the leakage of the loose material that exists in-between these two products. In reference to removing all the existing sheathing, you have to ask yourself exactly what am I going for and what do I expect. I do not know of any one here that would suggest doing that, any one that I support, so it is one of the areas that you live with what you have. Trust me, the numbers are far more complicated to review then to actually hear :) That only means that you have to arm yourself with the correct information, no matter how many months it might take to accumulate it, because you can do all kinds of shit wrong and you may never be able to hear how bad it is with nothing else to compare it to. Good luck, Brien

Thanks, Brien-- [quote]If you install an exterior grade plywood to the exterior of the 1X sheathing material that exists on the building and then you install sheetrock on the interior side of this same wall, you can effectively trap the leakage of the loose material that exists in-between these two products./quote] --I was hoping this was the case, but wasn't sure. This is probably the direction I will take: an additional layer of 5/8" OSB over the existing sheathing on three sides of the building, with an additional layer of exterior drywall on the side that faces the neighbors. I appreciate the advice. --Mark

sorry again..

Arsenic wrote:

My design is very close to this one.. So please forgive me if this is considered "hi-jacking"..

Please start a NEW thread to develop your build.

xSpace wrote:

Please start a NEW thread to develop your build.

Sorry.. The other board I follow is weird about creating new threads. I'll do this. Thanks for the headsup! :)