How to deal with Existing 3 Leaf wall

Hello, I'm currently in the process of designing a studio space in a building prior to purchasing the actual building itself. Discovered a potential challenge with the exterior walls of the proposed building. The building itself is a Mainstreet type storefront with storespace on either side. The structure was constructed originally in 1940. Walls adjoining other stores is comprised of (from our side to theirs) White coat / Brown coat / Hollow concrete block / Furring strip / sheetrock. If I understand the information here on the forum this is a three leaf wall that will allow the adjoining tenant to appreciate all the great drummers and bass players we will be recording. The space available within these three leaf walls with no other partition walls existing is approx 40' wide by say 75' with a few anoying columns right down the middle. The ceiling ht is 13'. I was originally planning on using these three leaf walls, as the outer wall, of a wall within a wall type construction. Now comes the head scratching. Obviously I can't make changes to the adjoining space (furring strip and sheetrock). Do I build a studio space that's a wall, within a wall, within existing walls? Or is that just adding an additional leaf........and thats bad right? Ummm ok, now what? I did search posts, found a great deal on the subject of multileaf walls (not that I understood much) but found no work around for this scenario, or guidance regarding a remedy. (edit 6/10 Uncomfortable with attempts to fill the block. Building is 40'+ tall and like I said built in 1940. Worried about integrity of block if I go poking holes in it.) You probably need additional information right? Tell me what you want and I'll provide it if I can. Thanks in advance for your input. Speaking of thanks, can you imagine what it'd be like sinking your life savings into a joint, building it out, opening for business and having the geezer next door complain to the powers that be and close you down! Yikes. So in other words, thanks for this forum! Bryant

Please resize the image as per John's dire warning...

Sorry about that, did the resize before posting and then attached the wrong one. The circles in front of my eyes are just now beginning to spin slower from all of the reading while searching on this subject. I hope you can forgive my indescrestion (sp?) Looking forward to your input. Bryant

Ok How about building a wall like below that's supposed to have an STC of 67 at some specified distance from the existing wall? If I don't attach to the exterior wall does this prevent an excess of leafs? Is there a more cost effective way to accomplish this?

Actually, since the "mystery distance" is somewhere between 10 and 30 FEET, your best bet (short of finding a different space) would be to build HALF of that wall but put ALL FOUR layers of 5/8 wallboard on the same side of the frame, such that your air gap between existing and wallboard is at least 12" - (not feet this time) I made some assumptions here - one, that the furring strips on neighbor side are "2x2's", 1.5" thick, and two, that your block are 1" thick web 8" thick overall. IF those are close, then the added furring/1/2" drywall will contribute a resonance (weak spot) at around 115 hZ, right where serious bass starts to kick in more or less :cry: 1" light concrete block webs have a critical frequency between 400 and 500 hZ, another dip in wall performance. By adding a second, free-standing frame with 12" air gap, you make the side of the blocks toward YOU, combined with the 12" gap and 4 layers of drywall, into approximately STC 75 wall with a m-a-m resonance around 23 hZ, and only a slight dip around 500 hZ. Don't cheer yet; this is BEFORE we deduct the weak spots of the other half of your block wall, centered at 115 and 400-500 hZ - these will weaken the combination of your side of the blocks and your added 4 layers of drywall, mainly at those two frequencies or near them - I've no way of calculating exactly how MUCH, but if you have that much space moving the drywall away from the blocks by another foot will help. The end result should make it so you'd need to be at around 100 dB SPL playing drums in order to just be audible next door - this is of course assuming no OTHER flanking paths for the noise, such as common floor slab :cry: If the space either side of yours is either vacant or has an understanding tenant, I'd set up some drums in your space and have someone kick the crap out of them while you're next door listening, so you can get a reference point - that should give you an idea whether the space has gaping holes or not - as it stands now, the kick drum and probably one of the toms (maybe the snare, depending on tuning) should be the loudest thing you hear, and they should be pretty noticeable. HTH... Steve

Alright, Thanks Steve for your quick response! I believe your assumptions regarding the block are correct as I doubt (don't know for sure) that they made thin wall block in 1940. In the rear of the space I'm attempting to use, the block is visible and is indeed 8x8x16. The furring, well.... I walked the adjoining space several months ago as it is for sale too. I observed some 2x4 framing that was exposed in a utility room to the rear of the store space on the adjoining wall but couldn't tell you what they used on the main space. I did notice that the wall has some electrical boxes for duplex and such but I couldn't tell you how large the airgap is for sure. Question: If their wall is furred with 2x4's instead of 2x2 what would that resonance freq be? Do you have a reference available with this type of info? Question: If I know that there is a weak spot at say 115hZ on the other side of the wall, is there a material that can be added to the plaster on my side (mass of the block wall) or as one of the layers of drywall that addresses the nasty freqs? Would surely like to avoid building a 13' x 75' helmholtz resonator if possible. :shock: Hmm do you maybe have a reference for this info too? Most of the architectural specs I've come across show the STC of the panel as a part of a wall assembly. I don't recall having seen specific freqs listed for a particular panel. That would be cool to have! Because I do have the space, I can place the inner wall at 2' or even 3' if that'd help. Regarding Potential for Flanking Noise #1 I know the slab is not common as the adjoining space is at least 12" higher. This may be a concern: The block does appear to be set on the slab and I assume the pour was monolithic (poured with a depression for the footers at the same time as the floor) For this reason I had considered floating a floor. From your comments I suspect this is not an option. #2 There are steel ibeam columns every 16' down this wall attached to cross member ibeams supporting the floor structure above. I suspect these ibeams could be a path for flanking noise. My plan at this time is to remove sections of the 2nd floor decking and framing to result in a higher ceiling in the main tracking space. The cross member Ibeams have 2x12 joist 12"OC with slat and hardwood laid on the span between them. Had planned on cutting hardwood and slat then removing 2x joist. This would leave the cross member Ibeams exposed above the tracking space but of course they would have to remain attached to the ibeam columns imbedded in the block wall. The ibeams at this elevation are 12" (they become progressively smaller on each floor for example 2nd floor columns and cross members are 10" and third floor columns and cross members are 8". ) I have not yet purchased the space. It sits about 8 hours away from where I currently live. What I'm doing now is costing out the design for the studio space and for a living space (third floor) to see what I can afford. By itself the shell is very affordable and it still might be worthwhile even if it requires some quirky acoustic fixes. I certainly understand the need to bang on some drums for reference and if I buy the joint the drums will be there, oh yes, they'll be there! But for the sake of costing, my optomistic hope would be to factor in the fix, not need to utilize it, and then use the cost savings to buy MORE GEAR WOOHOO. (One of Sharward's one man drywall lifts is looking pretty good about now or maybe a ribbon mike or three) My assumptions as to wall composition are based on visual observation while on site and a little bit of construction experience. Without whipping out a sledgehammer on a wall I don't own :twisted: .......tempting yes..... its just a best guess. For instance what if it's really two block walls back to back? Everything changes right? Thanks again Steve for your quick response to my earlier post. I look forward to any insight on the questions above and your thoughts regarding the potential for flanking on those Ibeams and any possible methods to curtail it. Haven't found any threads that address flanking noise from Ibeams. Surely it does resonate like a great big huge bass guitar string. Peace Bryant

Deeper furring (2x4) would lower this frequency to around 68 hZ (not good) - there is no "magic bullet" for specific frequencies, only more mass and wider air gap for the parts you DO have control over - so if that wall is furred with 2x4's, you'd just need to widen the air gap and maybe add another layer of drywall to the inner wall you're contemplating. References for this - sorry, proprietary software that costs $1000. OTher than that, you may find something free/useful here http://www.studiotips.com/ join, and you can download useful calculation stuff for free. I'm not sure why you think floating an entire room isn't an option; what did I say (link please) that led you to that? IF this is commercial space, the floor slab may be plenty strong enough for this. A fully floated inner room would eliminate 98% of any isolation problems, especially if you keep that extra leaf in mind when doing the side walls... Steve