Ceiling, frame joints and rockwool....

I'm about to start building my drum practice booth, which will be 310L x 220W x 210H. I'm planning to build a 2 x 4 frame and mount 2 x plasterboard on the outside and 3 x plasterboard on the inside. Door will be 2 double glazed sliding patio doors on the same strech of 2 x 4 frame. Anyway, I'm still very confused about lots of things, but have a few initial questions / problems. 1 - The construction will be at one end of my garage, and will be very close to existing walls. I'm trying to leave enough room to move around it to piece the frame together / attach outer wall, but this may be difficult. With the ceiling I will have difficulties putting on the outer plasterboard and screwing it in efectively due to the small amount of headroom. Any ideas? How do I attach the rockwool to the ceiling, given that I'll be putting it on from underneath ( - it will just fall back down on me...) 2 - What grade of caulk can I get away with? Will a decent bathroom type sealent suffice? 3 - How do I join the ceiling and walls together? I'm thinking of assembling the walls with the outer skins before tying them all together into the frame (due to the limited room to manouvre). Will it be ok to do this? 4 - I cant seem to get hold of any resilient channel. I was thinking of buying some rubber sheeting and spacing this in between layers 1 and 2 on the inside to give a gap and a decoupling effect. Any comments? Hope I make sense! Hy head hurts Cheers James

Unfortunately, I've got to run for a little while but I suggest you stop right now and read the reference material on this site. From what you described it sounds like you are heading down an expensive and possibly worthless pursuit. It sounds like you're building a triple leaf structure and that's not a good thing. I'll say more later if no one else chimes in. len

James, please start at the TOP thread in this forum; you've yet to edit your profile to include a location, so we can't very well tell you where to get RC or anything else... The more of the BOLD points in that "don't even THINK..." thread you can fill in, the better... Steve

You are missing something in the "leaf" count equation! You already have one leaf in your existing walls. Trying to build a new wall covered on BOTH SIDES with just enough room to get behind it is not only an extremely difficult task, it's also more than likely useless from an isolation standpoint. Steve was right - We need to know more information to be able to help. We have no idea where you are so some suggestions may be way off the wall for your area. In case you hadn't noticed, this board has contributors from all over the world. len

Sorry about that.. have updated profile, but I'm in Cardiff, United Kingdom. My construction will be built in my garage, which is single brick on all sides, new OSB roof coated with a plastic roofing paint. I was planning to build a 2 x 4 frame and mount 2 sheets of 18mm plasterboard on each side, filling the interior with rockwool. I hadn't regarded the garage walls as a leaf - it would be very difficult to insulate the entire garage effectively and sound leakage to the road is quite poor at the moment. My construction is a free standing room within the garage. I'm using the acoustics 101 guidelines from Auralex as a rough guide. Obviously I want to be as thorough as possible for my limited budget. As I'm in the UK, its harder to get some of the items that would be obvious to those in the USA, which is why I thought I'd try and invent my own style of resilient channel.. I'm familiar with the basic principles of sound insulation, and have built a booth before which was marginally effective, but lots of corners were cut (no stringers between studs, only 1 sheet of chip board on each side of frame, etc). It was rough and ready but worked enough to not disturb the neighbours upstairs in my old place. I specifically wanted to ask about caulk - is there much of a difference between the $2 a tube stuff and the $10 a tube stuff for the purpose of simply plugging all of the little holes and ensuring a seal? I'm also undecided about the doors at the moment. If I can buy 2 sets of double glazed sliding patio doors I may use them. Failing that, I'll buy 2 cheap firedoors and pad them out. The ceiling wont be accessable from the outside too much (garage roof low and I want to get the construction as high as possible - leaving probably a 20cm gap between top of booth and garage joists). For that reason I'll have to insert insulation for the booth roof from below. Any tips / advice gratefully received. I have next week off work to get started and I'm employing a carpenter to help me out (saves me buying all of the tools and as he's currently employed I'm getting a good deal...) Cheers James

Are your single brick walls exposed (in other words can you see the individual bricks and motar)? If so, you can gain quite a bit of isolation by covering the inside surface (in the garage) with a coat of motar or cement. Painting that gives you another dB or two. It's a cheap way to buy some isolation and it doesn't have to look all that pretty since no one will see it once the studio walls go up. You don't need to insulate the whole garage. Use the 2x4 framing (use 2x6s on the ends so you have enough wood to screw into after the first layer or two) and only drywall the INSIDE of the wall. Staple string or wire or something on the backside of the 2x4s to hold the insulation in. It's not that heavy so it won't need to provide much support. Just enough to keep it from falling out after you've put up the drywall. The insulation does very little for isolation. It's primary purpose as I understand it, is to be in contact with the drywall to damp it's natural resonance. I believe you also get a little better result if you use 24" centers instead of the more standard 16". I believe this lowers the resonance frequency. Take the drywall you were planning to put on the "outside" of the 2x4 wall and put at lleast one layer of it on the inside (for a total of 3 or more). The more mass you have, the better your isolation. Also make sure you get longer and longer screws as you add each layer - you don't want them falling down later because you are trying to hold up drywall with just a screw in drywall and not the stud. You should spend some time reading Paul Woodlock's Studio Build Thread on forum.studiotips.com. Ok, it will take a LOT of time (130+ pages) but he did an incredible job and did something with his ceiling joists that gave him some extra headroom. He's also in your neck of the woods (at least from this side of the pod it seems close). The PRICE of the caulk is not as important as the kind of caulk you get. You need accoustic caulk or don't bother with it at all. I got OSI-175 in the 29 oz tubes (the big ones) for only $3.00/tube. I'm sure they have a distributor there. Check the references here for building materials. I'm sure someone has posted a link to a caulk supplier over there. Hope that helps a little. len

Cheers for that.. I'm still a little miffed why plasterboarding both sides of the frame is such a bad idea - surely a double leaf 'room within a room' would be more effective? Aside from that, I dont want the garage wall to form part of the construction as the width of the garage is too wide for me, so if I dont put plasterboard on the outside of the frame the rockwool will be constantly exposed. Alternatively, what about if I do 2 layers of plasterboard directly onto the inner frame, then put resilient channeling on and do another 2 layers secured into the channeling? I've found a stockist of this now.. and a cheap supplier of acoustic caulk :) . I'd still have a problem securing the rockwool in between the frame though if there isn't board on the outside of the frame (the frame is totally freestanding, in case you were wondering..) I'm also a bit miffed about using longer screws as I put more levels on. Wont this result in sound being transmitted down the screws through all of the layers? Is there a certain type of screw that would be best to use for this reason? I'll limit screws to 4 per sheet anyway. Is it an idea to caulk around the screws before screwing in? And what length of screws? So many questions... :oops:

badass_mcfunk wrote:

I'm also a bit miffed about using longer screws as I put more levels on.

I don't understand why you are miffed about this. What do you expect the screw to "hold on to" if they aren't long enough to reach into the wooden studs? A screw into drywall (i.e., from the second layer into the first layer) won't stay up. You need to be at least 1" into the stud. The idea of more layers is to make it "appear" accoustically as one thick layer. 4 screws per panel WILL NOT HOLD! If you are going to insist on this, let me extend my condolences to your family now. You should have no less than 1 screw every 12" on inner layers and every 8 inches on the last layer. This is for safety more than anything else but by having lots of screws, you will also "bond" the layers together tighter so they will act as one thick layer. As to holding the rock wool in, as I said, just staple string back and forth across the back side to hold it in. Gravity is the only thing worry about here.

badass_mcfunk wrote:

I'm still a little miffed why plasterboarding both sides of the frame is such a bad idea - surely a double leaf 'room within a room' would be more effective?

The reason this is a "bad idea" is because you are NOT making a double leaf, you are making a triple leaf because you have to consider your CURRENT walls as a leaf unless you are planning to tear them out. I know it doesn't make sense logically but this is physics and it's been PROVEN to be the case. We aren't just making this stuff up. len

Len, Aside from the excellent advice you are giving Mr. McFunk, i have to disagree with one point you made ... insulation's purpose is not just to physically dampen vibrations of the drywall, it does help absorb sound. that is why, if possible/practical it is recommended to fill the entire cavity between leaves with insulation. the canadian studies have shown a direct correlation between more insulation and better isolation, up to 100 percent fill. the idea of dampening the drywall is certainly important too, but i wouldn't think it is even the primary benefit of insulation. insulation does affect sound energy within the wall, in the same way it works inside the studio, by turning sound energy into heat energy.

Thanks for your advice Len Just one more thing though.. If I am only going to put drywall on the outside of the frame, I'm not entirely happy about it just being held into the frame by string on the outside. Surely bits of rockwool fibres will come loose / float around in the air within the garage? I really cant understand why an extra layer of plasterboard on the outside of the frame wont help.. it will then be a few feet gap until the garage wall (which as I mentioned before is sealed poorly and too large to do anything constructive with).

Badass, i had the same plan as you initially, only a few feet from my room to the walls of my garage. in that case i was going to build a 2 leaf construction. say you were building this in a huge warehouse, of course you would build 2 leaves in that case. however the more i thought about it the more i though, why am i wasting this extra space that i can't do anything with, so i just made my room bigger, to the sides of the garage. so my exising garage walls are my outer leaf. however you would naturally seal up and "beef" up the existing garage walls if needed. i think you have brick so beef may not be needed. i am adding layes of wallboard to the iside of my original garage walls. it may be a lot of work to seal the existing garage walls but it's also a lot of work to build a stud wall right? anyway i think this is a gray area on the 3 leaf thing. i would say read up on why 3 leaves are bad and then after you are more knowledgable let your gut be your guide. just as an example, many of us are building what are essentially 3 leaf ceilings because there just is no other practical way to do it. but, go in with your eyes open, weigh the costs and etc. you don't need resilient channel if you have two separate walls. only if it is a single stud wall. you can't screw drywall to drywall, it has to be into a stud. if you go into drywall the screw will just spin around and around, and it won't hold. as far as the garage door i'm leaving mine in place but somehow adding gypsum sort of directly to it, and sealing the whole thing up. good luck

I don't know where you're getting all this 18mm plasterboard from, it sounds expensive, and heavy! Stick with 12.5mm SE, fiver a sheet from B&Q, and I guarantee 3 sheets of that will be cheaper than 2 sheets of 18mm. A brick wall outer is usable. At least in here in the UK we don't often see the hollow bricks that they use overseas, that would cause probs. Get the walls rendered internally, a nice thick layer will gain a few DB's of soundproofyness. After that, the weak points in the existing garage will be door, windows if you have any and the ROOF! Your brick walls are many many more times effective at soundproofing than a sheet of OSB, consider attaching plasterboard directly to the underside of the OSB and adding 2x2 between the joists to hold it up and prevent sag. If your joists are big enough (6x2 or more) then add 2 layers of plasterboard. Can you post some pics of the existing roof from the inside?? The advice you've been given so far is all good, use existing garage outer as one leaf and new walls as inner leaf (one side only!) I wouldn't bother with RC, you could use it to attach plasterboard on the existing joists, but the other way of using new joists-between-existing-joists will only cost you a couple of inches height and will provide much better isolation. Be sure to explain to your carpenter that the new room mustn't come into contact with the existing garage AT ALL, even one screw could erm, screw up your isolation. (Floor contact is of course unavoidable unless you want to spend thousands on a new floating floor.) Just because he's an experienced carpenter don't assume he knows anything about soundproofing. Another query, will this room take up the entire width of the garage or just be in one corner, ie: how many of the existing walls will it be 'right up against'

Thanks for all the advice The booth will just be at one end of the garage (which is also a very odd shape, hence me wanting to do a completely free standing construction without utilising existing walls). It will be in contact with the back wall and 2 side walls. Should I just render / board that section of the garage and then build the frame in there (still free standing, not attached to the rendered garage walls). There would then be (outside in) existing brick wall > render > 2 x 4 frame a few inches away not touching wall > rockwool> 3 x plasterboard on inner frame. On ceiling it would be coated OSB > joists > 2 x plasterboard > 2 x 4 frame > rockwool > 2 x plasterboard. In the other half of the garage the existing brick garage walls would remain unrendered with some sound leakage. The ceiling would also remain just OSB with no added plasterboard. Due to the size of the other half it would be a mammoth task to render it all and seal properly. .... what about the rockwool just held in to the frame with string on the outer frame side, given that the frame will not be in contact with the existing wall? Not sure this should be exposed, or have I got something wrong??

Dan Fitzpatrick wrote:

Aside from the excellent advice you are giving Mr. McFunk, i have to disagree with one point you made ... insulation's purpose is not just to physically dampen vibrations of the drywall, it does help absorb sound.

I probably overstated the case too often I get the impression from reading newbie posts that they think insulation is the same as mass and that clearly is not the case. It does have SOME effect but it's not the same effect you get THERMALLY with the same material. It would make an interesting experiment if some one took a big cardboard box, measured the sound coming from a boombox inside it, then covered it all with insulation and measured again. I think a lot of people would be disappointed. badass_mcfunk, I have built (ok, am in the process of building) an entire studio using the technique I described. There is no back on any of my walls and I used either wire or string in a lattice to hold the insulation in. Because my rooms are all completely enclosed, there are no floating insulation pieces to get into the air. The air space between the walls should be sealed from the rest of the house/garage should be as close to air tight as you can get it. I would also like to add that it is YOUR studio not mine. You can build it anyway you like. I'm not your neighbor and I won't be recording there so all of these decisions are up to you. You should note however that other than Dan's comment about insulation/isolation, note of the real experts on this forum (and believe me, I make no claims to being an expert) have jumped in and said my advice is a load of crap. Silence does not necessarily imply agreement but if someone starts giving bad advice, the moderators usually jump right in and try and correct the situation. len

No reason to jump in, other than a few minor clarifications - started a sketch but gotta go do "honey-do" stuff for a few hours, will answer this more after... Steve

I'm back; first, if you read through the first 2 or 3 threads listed in the REFERENCE section, it will explain a lot about walls and how they work - Second, the only time screws cause problems with leakage is in a single frame wall with multiple layers of plasterboard. The minute you go to separate frames the problem goes away almost entirely, because the insulation inside the wall attenuates the small amount of flanking caused by fasteners; the frame and the plasterboard ON the frame act as one unit, separated from the second mass by air/insulation. Third, acoustic caulk only SEEMS expensive; a decent household type caulk that might hold up (butyl based) here in the US costs around $4.50 per 10 oz tube; acoustic caulk comes in 29 oz tubes, and can be had for about the same as the butyl so the cost is actually LESS per foot of caulk bead. This is generally what you should be considering for best isolation - we still need to see/hear what your roof is like though. If there's room, a separate ceiling joist system is best rather than use RC or similar - separate frames always give better isolation, and if your roof is relatively light the extra frame would allow more layers of plasterboard to be hung safely... STeve

Many thanks Steve, looks like a good plan :D I have posted some photo's showing various aspects of the garage. I have spent a few hours looking at the reference section and also Pauls Studio diary and things certainly look clearer (I had read this section origionally, but it didn't make sense at first... I'm a drummer after all...). You will see from the photo of the left wall by ceiling that it is a double skin wall on that side, but the inner wall does not go all the way to the top. I was planning to mortar over the exposed bit of outer wall. I'm still debating rendering the whole lot - I thought it may be acceptable just to mix up some quick setting mortar and plug all of the bits that look dodgy. On closer inspection this evening, most of the wall is surprisingly good, and I am in the process of tanking the floor / up to 1 metre up the wall with Thorseal. I think as far as the outer leaf of my construction is concerned, the ceiling is the biggest problem. After the roof was fitted (about 2 months ago) the OSB got mouldy very quickly due to damp (hence the tanking with Thoroseal). I've sprayed and brushed the ceiling with mould killer and its fine now, but may return as ventilation in the garage when the booth is built may lead to condensation. To boulster the OSB I was thinking of putting sections of plasterboard against it and fixing by wooden notches screwed into the joists then caulking, but because of the damp / mould I'm worried about putting plasterboard directly next to the OSB. Any other suggestions? Obviously if I do a layer of plasterboard directly onto joists I'm back with the '3 leaf' problem. Any cheap / quick solutions? I've found a good supplier of acoustic caulk at only £2 per tube, so I'll be using that. The only other thing I'm unsure about is the doors. I'm thinking of 2 x solid internal fire doors from Wickes (£30 each). One will go in the main frame, the other in the stud wall (as per Steve's diagram). Can I do any kind of a small 'passageway' to keep the enterence to the booth neat? How do I do this without the wall / frame touching? Thanks once again for all of the great advice James

What is above the OSB? If you had it get wet before, unless you solve that problem, I'm afraid that you might get (deadly) black mold back and you wouldn't see it after you're finished until it's too late. Solve that problem first. As to rendering all the brick/block walls, I'd do it. It buys you isolation and isn't that hard to do. Of course, I'm not the one doing it. :-) len

The OSB is coated with some rubberised paint stuff - I had it done properly by a roofer. It was a really wet few days when he did it so the OSB got a bit damp, and with the added problem of the garage walls being damp this caused condensation on the ceiling side of the OSB resulting in mould. I'll give it another spray, but I'm concerned about adding another layer of anything without it being totally dry, which will be hard to achieve at this time of year. Any suggestions as to what I could add another layer with, given this? The walls have now been treated with waterseal on the outside and I'm tanking the inside this weekend so it shouldn't get damp in there again. Incidentally, I may render the outside of the left / back walls in the summer to add extra protection against penetrating damp. The right / front walls are already rendered. Cheers James

Me again.... I've thought of a plan for my troublesome ceiling: I thought I'd paint mould resistant paint onto the existing OSB, then fix plasterboard onto it, caulk the edges and paint with anti condensation paint. What do you think?? Also - Has anyone got an effective method for holding the insulation into the frame, so it doesn't drop out the back when its being inserted? String has been suggested, but this would involve me getting a staple gun or painstakingly putting small screws into each frame section. Would a strip of duck tape running down the middle of the back of each section do the trick? I've bought 80 slabs of 1200x455x50mm Isowool to make life easier. Bit on the thin side but a friend who does loft conversions recommended it - I haven't done accurate calculations but I think I'll have loads left, so will do some double layers. I start frame construction on Monday and have a hired hand all week, so I'll get as much done as possible. I'm expecting to have most of the booth finished by Friday.. time will tell. I'm floating a floor using delta fix acoustic battens, which seem quite cheap (£2 per metre). Cant find anywhere that stocks U boat type fixtures locally or I'd use them. Battend going onto concrete, isowool in between battens, 12.5 mm chipboard on top and then laminate flooring (if I can find some cheap). I'll leave a gap in between the edge of the battens (and everything that goes on top) and the inner booth wall so the floor is isolated from the booth walls. Better go and finish the damp proof membraning.. Still undecided about rendering inside as I'll be doing the exterior when its warmer. I realise it will make a difference but I really dont think I'll 'need' to do it - I can always do a really thick render on the outside if I find I haven't got the degree of sound insulation that I need. Thanks again James

badass_mcfunk wrote:

Also - Has anyone got an effective method for holding the insulation into the frame, so it doesn't drop out the back when its being inserted?

First off, a staple gun is only a couple of dollars over here at any office supply store or Walmart. It doesn't have to be fancy. A couple of alternatives are: 1) "Insulation supports" - These really amount to pre-cut pieces of wire that you just push between the studs and they are held in by friction. The wire is pretty stiff and I could find NO tool known to man that could cut one. They have little points that dig into the studs. 2) I ended up having to do this even with the insulation supports because they were really too long (and therefore they bowed in the middle). Get a small drill bit long enough (and sharp enough!) to drill through your studs. Drill holes about 1/8" away from the back edge of the studs every 12" to 18" vertically and then get some cheap wire and string it through the holes. It's not as hard or as time consuming as it sounds. len

I'd be really concerned about your wet OSB - when you paint over wet wood with ANYTHING, all you do is trap moisture so it can rot. If you don't have a dehumidifier available, I'd at least direct a couple of fans toward the damp spots and a heater, and let the wood dry before attempting any coatings. Otherwise you're asking for a big headache... Steve

The OSB isn't wet, and I dont think its even damp anymore - its certainly fine to touch. I'll give it a good blast with a hairdrier before painting it. I cant use a dehumidifyer in there at the moment because of the Thoroseal I've used for tanking - it may crack it. I'll give the OSB a bit of heat and paint with mould resistant paint, then cover with plasterboard and seal. Managed to find a staple gun for £6 and some garden wire to hold isowool into the frame. Still unsure about how to do the 'passageway' from the stud wall into the framed room. I'm assuming that a gap of about 10" between the 2 walls will be ok? I'm thinking of building an enclosure using 9 x 1 attached to either wall making a very short tunnel, which will tidy up the enterance and leaving a 1" gap where the walls aren't touching.

...Another problem. I've screeded the floor using a self leveling compound, but having just tried laying a length of 4 x 2 down, there are some small gaps under it. I dont think I'll get the floor 'totally' flat and even without proffessional help. Will I be ok to leave it as it is and caulk around the base of the frame? Any other solutions?

Get some Sill Seal. :)