Help / Comments - New Construction - Sort of...

Being on the second floor, I would give some special consideration to the rigidity of the floor system. This can be greatly enhanced by doubling up all the floor joists under this room - we're talking an extra few hundred bucks for lumber. In addition, the best scenario would also include T&G 3/4" plywood, glued and screwed (they'll probably be using nailers, so just go back on your own and screw it down w/ one foot spacing. The builder will probably insist this is all overkill, but it makes a substantial difference in the strengt of the floor, and can be accomplished for the price of a cheap "tweak" (and this is the only logical time to do it). Perhaps someone will suggest the best means (materials) for sound isolation to the lower level. Have fun, and good luck ... Tom

Make sure you get a good electrician that understands that he is not paying you to do the job...some of these guys like to do it their way.

Your dedicated room will make you a very happy audiophile...congrats.

Dave

"I have also requested the entire room be hung with double layers of sheetrock"

Double layers of drywall may not be a good idea unless you are going with a double wall. The added drywall will reflect bass back into the room I would think.

Short of a double wall construction I would think that 2x6 or more stud thickness will allow more insulation to be packed in behind the sheet-rock to absorb bass.

Dave

Tburn's advice is dead on. Cost is small rellatively speaking and reward is high.

As far as the walls and insulation it may be a good idea to type in room dimensions into an in-room frequency response Excell spreadsheet to find the problem frequencies and then read the appropriate chapters in Master Handbook of Accustics to fight the problematic frequencies. It is impossible to build the perfect room but you can build a damn good one.

Here's one place to start. Look through the rest of the site for excellent information on new construction techniques.
http://www.acoustics101.com/walls.asp

I think Tburn nailed it...

Thanks for all the responses thus far. In general would it be key to double up the floor joists under the room, or the 3/4" plywood screwed? Is it imperative for both? I am just asking in case the builder comes back unable to do it for the cost allocated. Should I request that rather than the double layer of drywall, or keep that as well.

The mention of the 2x6 had my thinking the walls were relatively thin on the innerwalls, perhaps 2x4 (if they go that small for inner wall) I am not positive on the house being framed that I walked through. I will have to drive over tomorrow and take a look again.

Is there an order of importance of what is "key" ?

Thanks for all the links too... some reading to do now.

Hi Audiofankj - in response to your question concerning the floor, IMO it would be most beneficial to double the floor joists, especially considering the fact that you use an analog source in your system. Without looking at the framing blueprints nor knowing what length of span is required, I would assume typical construction methods would entail using 2X10 joist lumber (and dependent on local building codes, the builder may be able to get away w/ using 2X8's). This, of course, is quite sufficient to carry normal second floor loads, but will still possess a certain amount of "flex". Again, doubling the joists will greatly strengthen the floor system, and while you're at it, spike the hell out of the doubled pairs (and to really get serious, lay some construction adhesive between the pairs before nailing) You are essentially forming "built-up" beams by doing all this labor. And timed right, you and some buddies could do this on a weekend (the contractor would need to know so as not to apply the decking before you got to it). As an aside, but probably prohibitive if working within a tight budget, is the availability of new types of trussed or plywood I-beam joist systems which could also be considered (you'd need to consult an architect on this subject).

Concerning the plywood, it pretty much depends on what the finished flooring will be, and how they typically do the work in your area. I would want a finished floor no less than one to one and a quarter inch minimum thickness. For example, if you go with a wood floor, this would equal approx. one and one-half inches finished. And, again, using construction adhesive on top of the joists before the subfloor plywood is layed will be of benefit.

Sorry - don't really know what level of experience/knowledge
you have with constuction techniques - kinda hard to know how to discuss here. If interested, just drop an email and we can discuss this ad nauseum. I was "complaining" to another AudiogoNer just recently that most of my forum participation is of the 'asking for help' variety, but this is one area that I can offer some suggestions. Regards ...Tom

Thank you Tom. I will shoot you an email later, as my knowledge of construction is very limited at best... I do think the builder we have chosen is using the "I beam" joists under the floor, but I will have to confirm that. Thanks again for all the input.

Ok, I stopped by the subdivision this evening. Our house hasn't begun construction yet, however another with almost exact floorplan is near completion of the framing stage. I think the builder is using what I think I have heard termed as "engineered lumber" ... all of the boards seem to be precut to certain specifications for this "Earth Craft" home... The joists holding up the flooring on the second story bonus room appear to be a 10" long piece of plywood sandwiched with what appears to almost be the size of 2x4's on either end by about 16 feet long (the width of the room)... side view they appear to look just like " I ". The total height/depth of the " I " joists was about 14" tall by the width of the room. The spacing seemed quite wide to me, about 18" or so... I wasn't able to get an extremely accurate measurement. The flooring was 1/2 or 5/8" plywood nailed in. I will most likely go back through when mine is being built and at least screw the floorboards in as well...

Any suggestions on what I saw? - Thanks again.

Just a heads up, Kirk - sent ya an email ... Tom

Audiofanki, they are called engineered I joists. The ones with the 2X4 on the top and bottom are the best. 18" centers, I would think more like 16" centers, hopefully not 19.2" centers. With these I joists the builder usually does not install any bridging supports between them. I would find out how much he would charge you to install solid bridging at least down the center span of the I joists. Sub floor 1/2" or 5/8"? Are you installing a hard wood flooring over this? another 3/4"? If not and it is carpet usually the subfloor is 5/8" min and even 3/4". An above post suggested a min of 1" to 1 1/4 thickness, that is a good idea but you need to get on the ball and talk to the builder. You may have a floor thickness issue of the area just on the other side of the room entry door to contend with.

As for your wall construction you may want to check out this site.

http://www.asc-soundproof.com/iso-diagrams.htm

Jim

Tom - Thanks for the email & advice!

Jim - It has been a monsoon here lately, I will most likely try to get up to the subdivision and get a better measurement on the I joists. From what I have seen so far, you are correct. There is no bracing between the I joists, and they seem to be spaced fairly wide at about 20" between the I joists. Is there a rule of thumb to follow or look up? Yeah the sub floor was either 1/2" or 5/8" - I will try to nail that down tomorrow as well. I will not be going with hardwood in that room, as the wife and I plan on turning it into a family room/children play area in 5 or 6 years, thus she wanted it carpeted. At that point I will move the system to the basement which will be a 16' x 24' room. But that may happen further down the road as well, thus I would like to make sure the floor has minimal bounce.

Do either of you feel that putting solid bridging supports down the center span will reinforce the floor enough? Or would you try to add a few more I joists and minimize the spacing between the I joists a few inches? If either of those are done and I am going with carpet, should I ask for another 1/2" layer on top of the initial 1/2" or 5/8"? Or does 1" thick exist and just request that?

As for the noise "isolation" I have a fairly accepting wife. She really isn't worried about me "containing" the sound much at all. Since the back wall (behind the speakers) of the listening room will back up to our beds headboard in our master bedroom I will be installing the "wide green insulation tape" ( found here : http://www.soundproofing.org/infopages/Tape.htm ) on the both sides of the studs on that wall. The isolation tape basically seems like a gasket material that will provide for some isolation to reduce the vibration and sound transmission from the drywall to the studs and through to the other sides drywall.

Also, do either of you feel the request for a second layer of drywall will be advantageous? I was thinking more rigidity of the walls would be helpful. If it really isn't helpful to double up the drywall, I will most likely transfer the funds allocated for the additional drywall to the flooring or joists.

FYI- I do have some time to work on this for a few weeks, as our contract just went in last week, they are working on the permits now and should be breaking ground in a few weeks... so by the time the basement is poured and the framing begins, I anticipate it to be at least 6 weeks or so away.

Thanks again for all the help.

I personally would not want the floor joists on 19.2" centers. Pay the extra for 16" center. Basically you would be adding one "I joist" for every 8' run. 16" center is a lot better solid floor. Something does not add up with the 1/2" sheeting over the floor joists. 3/4" min is usually used if covered by carpet. I bet the house you were looking at was 5/8" subfloor with 5/8" or 3/4" hardwood floor to be added over that.
Sounds like this is just going to be a temporary audio room.
I would forget the extra drywall and such. Save the money for the audio room in the basement. That will be a better room than one on the second floor. Especially if you want to crank up the volume.

Jim

Thanks again Jim. I am not fluent in builder/construction terminology, thus I am assuming if I ask the contractor to put the I joists on a 16" center, that is the amount of spacing between the I joists? The house in which I was measuring was not mine, just the same floorplan so I am unaware of what flooring they will be finishing in that room. However, as I am going with carpet you say to request a minimum of 3/4" subfloor? Even though this will most likely be a "temporary" listening room, it will still be five or six years, so I would have no problem with the double drywall of the walls - IF it will help at all sonically. We will most likely turn it into a small home theater room that doubles as a family room.

Thanks again!

Hello Kirk - I concur w/ Jim - I simply wouldn't accept any subflooring (plywood) less than 3/4", and I would further stipulate 1/4" (preferrably 3/8") underlayment before laying carpet. I will simply state - a finished floor thickness of only 5/8" inch would be a joke! And I also agree, since apparently the subfloor will not be all that beefed up, to specify 16" on centers for the I-joists. To check this, find the midpoint of the top flange of any joist (width/2) and place a mark - then do the same on the neighboring joist. Measure the distance between these two marks - that will tell you the on center (o.c.) spacing of the I-joists. Jim was also correct to recommend solid blocking between the joists. I did a quick read about wood I-joists on the net, and from what I gathered, they will still exhibit flexing, but this can be reduced with blocking. A lot of this depends on your builder - is he a hands on carpenter, leading the crew, or does he drive around to his sites all day, in a new pickup and carrying a briefcase. IMHO, the latter variety will cut every corner imaginable to add to his bottom line. 'Nuf said.
And to reiterate one last time, insist on construction glue being applied on top of the joist before the plywood is layed. Unless you are present during this phase, there is no way of knowing if this was indeed done, other than to find the empty "tubes" laying in the trash pile later. You need to tell the builder you expect to see these. Quite simply, there is either the right way or wrong way to frame a house. Again, best of luck ... Tom

16" center to center. Do not let the builder talk you out of it. If you can go into one of the houses being built just go to the middle of one of the rooms. Bounce up and down just a little, you will know what I mean. Even heavy walking across the floor you will fell the spring in the floor. If the joists are indeed 19.2" center to center you will want to change the specs on the first floor and the second floor. Now, you know why the builder is installing the joists the max allowed 19.2" center to center. The builder is cutting his cost one "I" joist for every 8' of run. Here is your problem as I see it now. You have already signed the contracts. If you decide you want to change the joist spacing to 16" CC The builder has the pricing leverage. Use your head when you talk to him.

Thanks much Tom & Jim - Much appreciated. I was able to drive over again today and re-measure. It does appear the current spacing of the I joists to be 19.2" center to center, I didn't measure this - don't know how I forgot but did measure just about all else. It is as follows, and hopefully not as bad as initially thought:

The I joists are a height of 14" exactly - that is including the "2x4" on each end of the I joist. They are being installed width wise of the room, approx just under 16 feet.

I measured the plywood subfloor to be 3/4" thick with the tape measure. However, stamped onto the subfloor was ' T&G Engineered - 23/32" ' I am assuming this means they are tongue and groove pieces of plywood? Full pieces were 47.5" wide by 8 feet long. They were laid in a staggered pattern as well.

Let me know if this will be sufficient for a subfloor, with the construction glue & 16" on center? Or should I also ask for blocking?

I did have my wife with me, and had her stand in the middle of the room and jump up and down a good foot or so in the air, and I was about a foot from her, there was approx 1-2" of flex noticable in the floor. However with her walking I could feel it, but not notice any bounce... again this may be different with a needle on the record.

Also, this house is just in the beginning stages... frame just went up, plumbing is going in now, and shingles being put on... as the windows were going in today if any of that is of relevance.

Thanks again. Any other thoughts on what to request of the builder before I talk to him? As of now:

- I joists on 16" centers

- minimum of the 23/32" T&G engineered subfloor (if acceptable to you guys?) construction glued to the I joists

Do I ask for the blocking? Or at this time, make certain he is aware I want the primary layer of drywall taped and mudded as normal, then the second layer laid on top and finished...

23/32" that is the thickness, nominal 3/4". Like a 2X4, if you measure it, it is not really a 2X4. The solid bridging in the sound room would be nice. What it will do, no matter where you are walking it will also transfer the load to the joists on either side of the one the weight is on. Did you notice if the T&G was screwed down. In my city it is. Glued and screwed.
Not sure why you want the first layer of rock mud and taped. If you are not going to use wall damping pads between the two layers of rock just make sure the sheet rocker uses a lot of wall adhesive between the two staggered layers of rock. Again glued and screwed. Not nailed. Bass will pop nails over time. Infact I hope the rockers in your area, screw all the rock in the house, not nail it. Also make sure the electrician knows this room will be double rocked. So he can set his rough-in boxes for the correct depth. By the way, any idea the distance your electrical audio oulets will be from the main electrical panel? Those dedicated circuits...

The flooring appeared to be nailed, however my current neighbor is a retired contractor and mentioned we could go over on a Sunday morning and sink screws into the floor after they had put it in. It seemed fine before, however with the construction glue, would that still be alright to go back and do after the fact?

The request for the first layer of sheetrock to be mudded was advice given to me, that if it is not, it won't be any more effective than just a single layer if both layers aren't mudded. Is this true? I was also told the second layer should be a different thickness to help break up the waves, as if they are the same thickness, it will almost act as just one layer is up and not really help with the transfer of sound. I haven't seen the drywall yet, however I would assume they nail the drywall rather than screw it - that is how most I have seen appear. Not sure about us coming in after the fact and screwing it in, as it will have to be re-mudded again...

again - any thoughts or advice greatly appreciated. Once we have all the "basics" down, I will compose an email stating my wishes on the construction of this room...

good tip to ensure the electrician knows the room will be double rocked to set the boxes at the correct depth.

The main electrical panel will be in the basement, hopefully somewhat centrally located... if that is the case, I assume I will need about a 20-30 ft. run of romex for each duplex...

I got a chance to go out and look at some new homes under constuction. In my earlier post I was mistaken, they are just nailing the sub floor to the "I" joists. Glued and shot down with a nail gun. "I" joists 16" on center. In regards to you personnally screwing down the subfloor, in the audio room on a weekend, I would not do anything in the way of work in the new house with out the builders permission first, unless you are the general and the builder is a subcontractor under you. He will not like it at all. Not to mention it could be a liability issue. If you want it screwed down have the builder do it.
You need to read the info on this website, every thing you ever wanted to know about about an audio room. You will find the answers to you drywall questions.

http://www.asc-soundproof.com/iso-diagrams.htm

Jim

Before you drive the builder crazy, I suggets you give him a good listem on some high end gear too improve his appreciation of your goals.

(probably best not to mention you are using cryoed wire and sockets, he will think you are nuts)

What is the idea behind the extra sheetrock? Are you going to have a gap between the layers with insulation? It would seem to me that making the wall more stiff (cement like) would reduce flex and redirect bass freq's back into the room?

Are you thinking two 1/2 inch layers? You may want to ask Rives or someone at his acoustics forum over at the Asylum weather two half inch layers would have any benefit over one 5/8's layer...I think not but I could be wrong.

As much insulation as you can possibly stuff behind...and then some extra may be a better idea. I did a double wall build when I did my room but had to do most of the work myself because the contractor would not have put up with all the extra crap I wanted for any kind of price I could ever pay...seems those guys are in a hurry to get to the next job...something about time being money I think he said.

Dave

Spoke with the builder and the I joists will be 16" on centers, subfloor is 3/4" screwed and glued. It sounds like the wall that is "shared" behind the speakers in the listening room, and behing the headboard in the master bedroom will be address with a stagger stud wall... most likely with some type of isolation tape on the studs behind the sheetrock.

Hi Kirk - good deal - sounds like you're on your way! Best of luck with the new home, and of course, the listening room. Now, if I could just get this hum to go away (heheh) ... Tom

Audiofankj, Just curious, will you be using any type of damping material between the two sheets of sheetrock?

Jim

Hey Jim-

At this point, no. Just staggering the second layer of drywall, and it should be a different thickness as well. I will be utilizing a damping material tape on the studs, and will be "stagger studding" the wall that the listening room and the master bedroom share. If you have any recommendations let me know - especially if they are reasonable in cost!

Kirk

Kirk if you are not going to use a damping material between the two sheets of rock I don't think it will make any difference if the rock is of two different thickness. I would probably just use two sheets of 5/8" and apply PL200 adhesive every 12" so the two sheets can not vibrate against one another caused by heavy LF bass from the audio system.

Jim

Thanks Jim-

Do you think it is best to just go with a single layer of sheetrock or to go with the dual layers and the PL200 in between? My concern is I may not be present when they are putting the rock up and will really have no idea if they use enough of the PL200, let alone if they use it at all...

Would appreciate your thoughts, and thanks again.