Framing walls to existing drywalled ceiling

Hi All I am about to start building walls on top of a floated floor for my control room (a few pix are here). There is a layer of existing drywall on the ceiling and I am wondering about whether or not to remove it prior to connecting the walls to the ceiling joists. The attached drawings illustrate the issue. Can anyone make a recommendation? Also… If RC is not used for second layer of drywall on ceiling will the consequences be dire? Can anyone recommend a vendor from which to purchase acoustical sealant online at reasonable cost? Does anyone have experience with a product called “quietrock” that is sheetrock with a high STC rating (supposed to eliminate the need for RC)? Thanks for any advice anyone can offer – I can get a lot of it from local contractors, but it is not always clear that they have the appropriate acoustical sensitivities! :?

scalpshifter wrote:

Does anyone have experience with a product called “quietrock” that is sheetrock with a high STC rating (supposed to eliminate the need for RC)?

This question has been asked and answered. Using the "Search" feature to look for "quietrock" (one word) will turn up many threads about it.

Thanks very much for the info on quietrock - way out of my budget! Much appreciated - I'll be more diligent about using the search function e

Perhaps I'm misunderstanding something. Are you connecting the new walls to the existing ceiling? If so, I don't think you want to do this. You want to build a new ceiling on top of your new walls so the whole assembly (floor, walls, ceiling) floats. At first glance it looks like you're rushing into this, but maybe you're not I dunno. There are several garage studio builds to reference at on this forum. I would check a local drywall supply house for acoustic sealant. I've dealt with 4 different drywall suppliers for my little project and all of them carried some type of acoustical sealant at around $3.50 for a 29 oz tube. I'm not one of the experts here, so take all of this lightly. Best of luck

yeah man that doesn't make sense to me either ... the whole point of floating the room (i see you've already done the floor) is that it does not touch the exterior leaf or structure in any way. also i wonder how heavy your inner floor leaf is (no more than 1" of wood at the most it looks like) ... it may not too late for you to add mass to the floor, which will imporve your low freq performance by lowering the resonance frequency in your floor cavity. right now your floor as it stands will amplify some audible frequencies ... do you know which ones :) ... being that you are on a slab you may still be ok but this might be worth checking into dan

Thanks for the input - very much appreciated. I have been planning this project for about 6 months and have gone through several design iterations with some input from people in this user group but I have no doubt that there is PLENTY of room for improvement. My goals are a bit different than average so I have made some design decisions that seem (and well may be) strange. I do not record live bands so sound isolation in the in to out direction is not top priority, but sound isolation in the out to in direction (screaming kids, tractors, etc.) definitely is. I want my control room quiet, yet I only have 8’3” of vertical distance in the structure within which I am building the room. Thus, with the floor height, and a dropped internal (inside the control room) ceiling consisting of 2 layers of drywall and RC, I will have just over 7 feet of vertical distance. I am going to then lose another 3 inches or more with baffles/absorbers that will be attached to the ceiling to eliminate ceiling reflections. When this is done I will not have enough vertical room for a self-contained ceiling. My compromise was to attach the walls to existing ceiling joists and then suspend a ceiling (as described above) within the control room to minimize sound transfer. I understand that this is less than ideal and I would appreciate any suggested alternative approaches. It seems like this approach has worked in some of the basement studio project I have seen on this site. In answer to one question the floor has two layers of 3/4 inch sheathing glued and screwed to a lattice of 2 x 6 (12” OC) with cross bracing every 2 feet (also screwed rather than nailed together). I used a weight calculator spreadsheet and it suggested that the room would weigh about 7000 lbs fully loaded. I used that number, and an empirically determined compression factor for EPDM (which, I know, is a non-linear spring…) to estimate the number of square inches of EPDM required to achieve a minimum of 10% compression (assuming I will add more gear over time and the room will increase in weight). I am planning to build a second layer of walls (on the slab) that will create more mass/air separation between rooms – but I am being careful to avoid multiple leaf systems. The real weakness of this design is the ceiling but I have not been able to think of any reasonable alternatives. Thanks again for your input!!!

Whats above this ceiling? Is it attic space? Still dealing with ceilings a bit myself, but I think you can take the drywall off and drywall above the joists. This creates the outer leaf. Probably good to do if you can whether you are floating the ceiling or not, because it gives more airspace between leaves. An alternative to floating the ceiling is RC or Kenetics sells "better than RC" ISOmax clips that are decoupled with vinyl and increase airspace. There are many models for different apps. Also look into RSIC clips. they are similar and I dont know which is best. (I think Kenetics)

That is GREAT - I was just out there holding a 2x4 above my head thinking if I could live with 8 inches of air above my head when standing in there - your idea of flipping the drywall above the joists (yes there is an insulated attic above) is primo - gives me more head room (no pun intended) and makes the task more tractable. I am still debating attaching the walls to the existing ceiling joists rather than building an independent ceiling. The longest span of the room is 18 feet, which seems to be too long for 2 x 4 construction. So…. I am leaning toward connecting the walls to the existing ceiling joists. No matter what I do it sounds like removal of the existing drywall is a good idea! I’ve contacted Kinetics about there products - thanks again for the lead. One question about the walls that are on top of a floated floor – I’ve seen suggestions for putting a decoupler (EPDM or neoprene) between the bottom of the wall and the floated floor AND I’ve also seen the alternative of connecting the wall directly to the floated floor. I am planned on doing the latter - is that a bad idea? Thanks!

Whether you pull down one layer of drywall off the ceiling and replace it with two above the joists, or you add one extra layer to your existing ceiling, be sure your joists can handle the load. Drywall is heavy, and a collapsed ceiling would hurt like hell if you lived to tell about it. ;)

scalpshifter wrote:

The longest span of the room is 18 feet, which seems to be too long for 2 x 4 construction.

Most definitely! :shock: Not even with just one layer of gypsum! Nor would it pass code!

So…. I am leaning toward connecting the walls to the existing ceiling joists. No matter what I do it sounds like removal of the existing drywall is a good idea!

Have you considered: (1) removing existing drywall from ceiling, (2) adding new drywall above attic joists, (3) attaching new "inner" ceiling joists to tops of new inner leaf walls, where the joists run in parallel with your existing ceiling joists, tucked up and in between the existing joist spans, and then (4) attaching your inner ceiling panels to the new joists? Think about it: You could use 2x6 or even 2x8 joists on your inner ceiling, but much of the joist height could be tucked into the cavity you reveal by "moving the outer ceiling up." :cool: There are threads on this forum with photos/illustrations of that concept. (I'm afraid I don't have time to look for them right now.)

I’ve seen suggestions for putting a decoupler (EPDM or neoprene) between the bottom of the wall and the floated floor AND I’ve also seen the alternative of connecting the wall directly to the floated floor. I am planned on doing the latter - is that a bad idea?

Steve has said that if you float a floor, there's no need to float the walls on the floating floor. In theory, your entire "inner room" can be firmly fastened to itself all over the place -- it's firmly attaching the inner box to the outer box that you should do your absolute best to avoid. That's where the flanking happens! Hopefully I haven't misunderstood your situation or confused matters. I've been known to do both! :roll:

Hey Scalpshifter...just took a look at your floor...lookin' good! :D

Nice keith. Thats the ceiling problem Ive been working with.(Not to mention my cathedral ceiling dilema, which is looking good, or Im refusing to deal or worry about). Im looking into the possibilities of double joists, added collar ties, and maybe trusses(if I can figure out how). Im sure I need structual help, and in this case I think there are answers. Check your deal out my friend. A studio that caves in never can recover its former glory and reputaion. The one thing youll learn here is if it sounds easy, promising, inexpensive, or simple its probably not true or effective or it can suck worse. Thanx Steve "the truth teller". At least my origanal plan was cheap simple and looked cool. Welcome...

The addition of inner ceiling joists is a cool idea - I'll find the thread and check it out - thanks! Here is the Midwest it can get COLD for 5-6 months with a foot of snow on the roof - so in addition to the concern of extra internal stress on the existing joists I have to be sure that they do not have to dig out my frozen carcass in the spring due to the external stress from the snow! I've had enough stuff fall on my head already and I need the few remaining neurons... My current plan is to build the inner walls on the floating floor and, for lateral stability, tie them to the existing ceiling joists with decouplers made from EPDM (I still have LOTS since I bought 10 lineal feet, 3 feet wide, and used about 3 inches!) and angle or some other type of bracket. I read through the Kinetics site and got some ideas based on their products. My goal is to allow the walls to move a few millimeters in the vertical direction as the floor moves down (with added weight) but, as suggested, NOT let the walls be mechanically coupled to the ceiling (while at the same time not letting them cave in when I shut the door).

I have a multi-leaf issue with which I am grappling. I have read a number of threads about the problem (though I have not found the actual theoretical explanation of the problem – but I am still looking). In my case, the internal double framed wall necessarily approaches the external single framed walls at 12-degree angles (please see diagram below). This creates a non-uniform multi-leaf problem that I expect will intensify as the walls get closer together. I understand that when this problem is unavoidable the best approach is to make the adjacent walls(s) more robust (the add mass rule). I would appreciate any suggestions about how to handle this problem and any pointers to a discussion of the theory of leaves and transmission loss. In the just for laughs department…. Based on the size, modes and empirical data from my existing CR, I am expecting this room to have some definable bass frequency problems so I was thinking about building Hemholtz filters at the multi-leaf weak points as energy sinks for some of these frequencies. The orientation of the filters will be 12 degrees away from optimal with respect to the standing waves and I can not get my head around :? the effects they might have on weakening/strengthening sound transmission through the wall. Any thoughts?

take the drywall off the inner side of the wall if you can . yuo can also beef it up(outer leaf) by putting drywall inbetween studs. alot like the roof.

Actually, looking at your diagram. You have 4 leafs(i think)(as long as the outer wall is sealed, ithink) If it aint built yet, read more about 2 leaf rule, and check with an expert.(like steve)

scalpshifter wrote:

. . . EPDM (I still have LOTS since I bought 10 lineal feet, 3 feet wide, and used about 3 inches!)

Ouch! So, you found the places selling the stuff with a 10 foot minimum, too, eh? I was lucky -- I was able to buy a "scrap" of EPDM sheet, 60 durometer, 3' x 2' x 1/2", for about $75 delivered. However, before you congratulate me, realize that I may end up not using any of it on my project! :oops: Also, Mike is absolutely correct. Think of sound traveling from inside to outside (left to right) and how many layers of mass it travels through in your current drawing:

1. Inside layer(s) of wallboard on first frame 2. Outside layer(s) of wallboard on second frame 3. Inside layer of wallboard on original wall 4. Outside layer of "whatever" on original wall

Remember, a "leaf" is defined as a barrier of mass. The walls inside your home are two leaf -- typically one layer of gypsum wallboard on each side of the wall. (Notice the difference between the term "leaf" and "layer": one leaf can have many layers.) That's single wall, two leaves. It also happens to be a pathetic two leaf system -- each stud is a flanking path, because the outer leaf is not decoupled at all from the inner leaf, and each leaf is weak because it only has one layer of gypsum wallboard. Making sense?

Yes - that all makes sense - thanks! The inner double frame section is decoupled from the single frame section at the bottom due to it (the double frame) resting on the floating floor. But at the top - depending on how I ultimately figure out hot to connect things with minimun mechanical coupling - there will be some flanking - no doubt about it! Also, the walls I build will have two layers of wallboard to help in the mass department. I am still interested in the theory as to why multiple leaf systems compromise acoustic isolation so I am on a quest to sort that out. BTW - I pulled down a section of the existing ceiling to find a lot of insulation and some cross bracing that will make drywalling from the other side a challenge (plus the attic is tight - space wise..) So I took a break and ate some lunch..... I think that ultimately I am gonna have to tear down all the existing ceiling - but I have to psych up for that!!

scalpshifter wrote:

. . .walls I build will have two layers of wallboard to help in the mass department.

You may need more than two layers. My latest "drawn" plans consist of three layers, and my latest "not yet drawn or fully decided upon" plans call for four or even five layers.

I am still interested in the theory as to why multiple leaf systems compromise acoustic isolation so I am on a quest to sort that out.

Think of each wall being a "repeater" of the wall closest to it at certain frequencies. The mass of the third (or subsequent) leaf will reduce some sounds but amplify others. Other than that, just know that it's a law. I don't need to know how or why gravity works the way it does -- I just accept it. ;)

I pulled down a section of the existing ceiling to find a lot of insulation and some cross bracing that will make drywalling from the other side a challenge (plus the attic is tight - space wise..)

Post pictures. :cool:

Thanks for the great info. It makes sense... My problem is that I am a scientist/inventor by day so my brain is wired to try to understand everything (even graviton exchange) - which usually leads to either total frustration (95%) or some cool discovery (5%)... In the interest of minimizing clutter I was going to archive my project photos at this link, but I'd love to post some here if it is OK with everyone. I am a skinny dude and the existing wallboard is 5/8 thick and 12 feet long (i.e., heavy) so I guess it comes down in 4 foot sections :) I'll go snap some pix of the fiasco and post 'em shortly. Thanks again

OK here we go.. I have a gallery at this link that shows the attic space from above, the hole I made to increase the amount of work I have to do, and the attic heater which is being moved. The HVAC is being done professionally and will involve relocating the heater to another section of the attic (far, far away) and running the appropriate ductwork to minimize noise (or so they say...). Check out the home made intake plenum - I did not construct this but it is amazing - requires at least 8 filters at a time! :shock: I'd really appreciate opinions about whether or not I need to remove the ceiling - put it on top of the joists - before dropping a floating one in the CR. I am out of GOOD ideas about how to attach walls to the ceiling joists with the existing drywall in place.

Earlier, I wrote:

Have you considered: (1) removing existing drywall from ceiling, (2) adding new drywall above attic joists, (3) attaching new "inner" ceiling joists to tops of new inner leaf walls, where the joists run in parallel with your existing ceiling joists, tucked up and in between the existing joist spans, and then (4) attaching your inner ceiling panels to the new joists? Think about it: You could use 2x6 or even 2x8 joists on your inner ceiling, but much of the joist height could be tucked into the cavity you reveal by "moving the outer ceiling up." :cool: There are threads on this forum with photos/illustrations of that concept. (I'm afraid I don't have time to look for them right now.)

Well, I just had a bit of time, and I found this one. There are some great CAD illustrations on the bottom of the first page. :cool:

Thank you awesome Sharward for the kickass span calculator link which tells me that with two layers of 5/8 inch drywall (weighing about 2.3 lbs per square foot) I should be fine using 2x8 Douglas Fir for a maximum span of 18 feet and a maximum live load of less than 10lbs per square foot. One consideration is that my room is not square, but since the longest span is about 18 feet, the rest should be gravey.... One queston: should the "internal" joists rest on both parts of the double frame wall. It seems that that might short circuit the walls, but if the joists rest only on the internal frame, the outer frame presents the same old problem of where to attach it at the top... as always - thanks for everyone's advice!

Hey, Mr. skinny/mad scientist/crazy inventor/masochist :wink: first, join the club; second, for a half-assed explanation check out my last post, last illustration on may 30, here http://www.johnlsayers.com/phpBB2/viewtopic.php?p=26761 Next, your pix confused me; is that an A frame with an attic, or wierd trusses, or??!? can you either get a wider shot of roof framing in the attic, or at least a sketch of what goes where framing wise? Thanks... Steve

Hi Knightfly Thanks for the post - you have to be one of those guys who can survive on 2 hours of sleep, based on the number of questions you answer on this site!! I'll snap some more photos and see if I can figure out the truss design well enough to draw it if the photos don't make sense. To me it looks like a more or less generic prefab truss design (the kind you see stacked together on 18 wheelers on their way to a construction site) with some cross bracing. But what do I know (molecules, no problem.... trusses, back to the library :) . The room is a north to south (meaning the spine at the top runs N/S) "shop" attached to a E/W (i.e., orthogonal) garage. It is about 28 by 30 feet total, with 2/3 on a cement slab and 1/3 over a "tornado shelter" which is a narrow basement hallway with cement on both sides and a wood framed ceiling. I'm attaching a sketch of the general floorplan. It has changed slightly - the tornado part (not over cement) is the left hand section. I checked the link you suggested and did find some info on STC values for single and double framed walls and the multileaf concept - but it was not a May 30th posting so I am not sure I got the info you intended me to - still it is a great help, right on target, and I'll go digest it for awhile. Pix shortly..thanks again! e

Here is my interpretation of the general truss structure for the shell within which I am building the studio (please see attached, not to scale, figure). One of my (many) concerns is that if I build a double framed wall (inner and outer leaf structure) things will be wacky (scientific term) when that structure approaches the existing shell which already has sheathing on the inside and paneling on the outside (and I am not sure about what is in between these layers). I have read about "at what distance does a (non-proximal) wall become a leaf (sounds kinda zen), but did not dissect out a precise answer. There may not be a precise answer since the system is a continuum (but probably not linear?) and it might boil down to whatever threshold one is willing to establish in terms of sympathetic resonance and all that). This is why I am trying to better understand the theory of multi-leaf structures. I just want to avoid any totally bonehead decisions... I'll turn on the babble governor now...