yet another basement

[musicman74]

First I'd like to say this forum rocks! I've been reading endless posts and gathering mass amounts of info(my brain hurts ) Anyway, I've done some homework and think I'm ready to start building, would just like to make sure I'm on track.
For now I want to build the live room and focus on the control room when more time and money permit. My goal is to achieve a decent amount of isolation fromthe upper level and vice versa(footsteps,t/v etc)and to and from the outside as well as the preposed control room. Again, it doesnt have to be totally isolated, just want to get the most bang for my buck.
I play in a moderately loud band and isolation toand from the outside is fair(no complaints from the neighbors in2+yrs)Would like to improve upon it somewhat though.Ihave a modest digital recording setup which will stay in the live room for now.
The plan is for a jam room/recording spacein the back half of my basement. Attached is a crude drawing of the space. Ceiling is 7'6" tall except where the hvac bulkhead runs it's 6'6". Joists are 2x8 and have a 12' span. The wall pictured between live and control rooms is a wood stud frame on 16' cntrs. the 2 long walls in live room are cinderblock-2x2slats-insulation-1/4"paneling. The back of the room is a wall of builtin closets 2'deepfrom floor to ceiling. the floor is concrete slab. There's a gas line that runs parallel about 1' from bulkhead below floor joists(had 12x12 acoustic tiles on2x2 slats, the line is flush w/slats).
My idea is to fill the ceiling with mineral wool(2 layers of 3 1/2" bats)and mount 1 maybe 2 layers of 1/2" or 5/8" drywall on resillient channel. For the wall between live and controlroom: 2 lyrs drywall on RC on2x4 wood studs fillw/ mineral wool and 2lyrs of drywall on CR side. For the 2 long walls(Currently cndrblk-2x2 slats-1/4" panels) I would like to conserve space and use the existing slat frame, fill with 2" rigid insulation and mount 2 lyrs of drywall on RC. Am I in the right direction? I need to come up w/a door solution for the55" opening. Wanted french doors but dont think I'll get much isolation. Maybe sliding glass?
I was also wondering if I could reuse the 1/4" panelling in my mass-air-mass wall plan or would it be too much for the RC?Will 2 lyrs of rock on RC be ok on joists w/12' spanfor the ceiling?(I should add that the RC will be run parallel to joists, mounted to the 2x2 slat framing that was for clng tiles)
Sorry for the long winded post, just wanted to give as much detail as possible. Hopefully I'm on the right track and appreciate any advice you can give.A donation to this great site will be in order for any help given.
Thanks again!

Keith

[knightfly]

Hi, and welcome to the board -

First -

For the 2 long walls(Currently cndrblk-2x2 slats-1/4" panels) I would like to conserve space and use the existing slat frame, fill with 2" rigid insulation and mount 2 lyrs of drywall on RC. Am I in the right direction?

No, see the attached drawing of what you propose, and why it's not the best idea -

I need to come up w/a door solution for the55" opening. Wanted french doors but dont think I'll get much isolation. Maybe sliding glass?

Sliding glass might be a bit better if you get a GOOD one (not cheap) but french (exterior rated) should be about as good and will allow full use of the opening. Otherwise, consider building the wall out for a 4 foot rough opening and building your own door, if you're fairly brave

Hope this helps... Steve

[SB]

are there transmission loss numbers that go with the block diagram, or am I just not seeing them?

[musicman74]

Steve, thanks for the reply.
From looking at your diagram I'm assuming that my idea would be the first one pictured which would be a 3 leaf wall?I forgot to mention that the other side of the wall w/out the opening is the exterior and is underground except for about the top 2'.

Assuming the block is hollow would it be best to remove the 2" furring and mount the gypsum directlyto the cndrblk?

Will I need a vapour barrier or should I just paint the block and use adhesive to attach gypsum?I remember reading a link about mold problems w/vapour barriers somewhere, not sure.

I'd like to "recycle" the 1/4" paneling as one of the layers, could I construct as follows - cndrblk(painted)-1/4"paneling-1 or 2 layers of 5/8" gypsum?

I suppose using RC on this wall will create a 3 leaf wall but i'm planning on using RC on wall between live and control rooms and on ceiling, will this work?

As for the ceiling,it has 2" furring strips perpendiclar to the joists. I would be mounting the RC to the furring then 2 layers of 5/8" gypsum. Will this hold up?

Should I fill between joists w/3" or 6" of mineral wool?

Thank you again for your time,I just want to make sure I don't make things worse.

Keith

[knightfly]

"are there transmission loss numbers that go with the block diagram, or am I just not seeing them?" -

I KNEW that question would come up immediately after I posted that; truth is, I've NOT done calcs on exact TL's on these; some are available at the many Canadian posts on wall construction, look in the REFERENCE section links. Others won't be there; I was mainly trying to explain what a LEAF is, and which types of add-ons will make too many leaves. I've had no extra time to finish this, I hope to do that and add it to the REFERENCE section in future.

From looking at your diagram I'm assuming that my idea would be the first one pictured which would be a 3 leaf wall?I forgot to mention that the other side of the wall w/out the opening is the exterior and is underground except for about the top 2'.

Right, it would be 3-leaf. If you're using a sub and mixing loud, or recording drums/bass, you would notice the loss of LF isolation by doing this - if you have no neighbors, it doesn't matter at all...

Assuming the block is hollow would it be best to remove the 2" furring and mount the gypsum directlyto the cndrblk?

Acoustically, yes. For other considerations, it gets trickier.

Will I need a vapour barrier or should I just paint the block and use adhesive to attach gypsum?I remember reading a link about mold problems w/vapour barriers somewhere, not sure.

This is one of those "other considerations"... I'll try to clarify things, but will probably just end up confusing BOTH of us - Anything you put on a wall, including paint, may act as a vapor barrier - latex paint usually won't act as a barrier, but oil base generally will. Plasticized gypsum panels, plasticized 1/4" "wood grain" panels, etc, WILL act as a vapor barrier. So will the paper backing on insulation, although this is a VARIABLE vapor barrier (sorta) it's safer to NOT have backing on insulation unless it's where you WANT a vapor barrier to be.

Generally, where the barrier should be is nearest the WARM side of the wall - for cooler climates, you will be HEATING the room so the vapor barrier should go toward the INSIDE of the wall, on the studs behind the wallboard. If you use plasticized wallboard, FORGET the vapor barrier because this would give you TWO barriers, in between which you will grow stuff that would make Alexander Fleming very proud Also, if you use a couple of coats of oil-base paint on the inside surface you should NOT put a vapor barrier inside the wall, for the same reason.

Are you starting to see why the answer about putting gypsum direct on your block walls isn't easy? If your block walls have been SEALED to help keep moisture under control in the basement, that's a vapor barrier - if you now add gypsum, and full-face laminate it to the block, the glue may also act as a vapor barrier - then, another layer of gypsum, your old panels (possible vapor barrier) and the wrong kind of paint, and you could end up with several barriers, between which moisture will get trapped and do NASTY things.

I've asked Rod Gervais to check in here and add his recommendations, since this can get so tricky; I think, lacking his advice to the contrary, that I would (assuming you actually NEED more sound proofing here) (and assuming your blocks have been sealed) strip-glue the first layer of wallboard onto the block using construction adhesive, and pushing the boards HARD against the block to squish the adhesive as much as possible - then mud and tape, put the second layer up at right angles to the first, and again strip-glue with construction adhesive - I don't know of a good way to fasten wallboard direct to block using actual fasteners, without defeating the purpose of the extra gypsum; I would NOT use this method for CEILINGS, however. Put whatever finish you want on the last layer of wallboard, but do NOT put anything I mentioned above that can become another vapor barrier; you likely already have one in the form of your sealant on the surface of the block wall.

I'd like to "recycle" the 1/4" paneling as one of the layers, could I construct as follows - cndrblk(painted)-1/4"paneling-1 or 2 layers of 5/8" gypsum?

If you follow the preceding paragraphs, and your paneling has a waterproof finish of any kind, the answer is no...

I suppose using RC on this wall will create a 3 leaf wall but i'm planning on using RC on wall between live and control rooms and on ceiling, will this work?

RC is fine (or RSIC clips and hat channel) where both sides of a frame have mass attached - under those conditions, resilient mounts on one side will help mid and high frequency TL, but NOT the lows. Only mass and wider air gap will do that. If you have double frames, for either a wall or ceiling, then don't use any resilient mounts; exceptions would be when an added wall has hard contact with the rest of the structure; then, the RC will decouple the wall surface from that structure and improve flanking noise.

As for the ceiling,it has 2" furring strips perpendiclar to the joists. I would be mounting the RC to the furring then 2 layers of 5/8" gypsum. Will this hold up?

This depends on how the furring is fastened to the joists; if by screws and they penetrate the joists by at least 1 inch with properly sized pilot holes, then sure; otherwise, I would re-attach them properly.

Should I fill between joists w/3" or 6" of mineral wool?

Whether ceiling or floated floor, a complete fill with light compression on walls and light to medium compression on floors - if rockwool in ceilings, you can save a bit and just let gravity help you; the object is mainly to have the insulation rest against the panels, so they are damped and don't ring. For a (floated) floor, gravity doesn't help. If batts aren't quite thick enough to press lightly against the underside of the flooring, you can use unfaced fluffy fiberglass batts cut into strips about 1/3 to 1/2 the width of the joist cavities, and lay these on top of the other insulation before adding the vapor barrier and floor on top of the joists... Steve

[z60611]

"are there transmission loss numbers that go with the block diagram, or am I just not seeing them?" -

I'd bet that several of those are described in "Noise Control In Buildings" by Cyril M. Harris

[knightfly]

Yeah, Bob, I think so too; if you're feeling ambitious, I'd gladly accept any numbers you come across; I can add them to the drawing and re-post it, seems like it might be a good addition to the database for a LOT of people... Steve

[rod gervais]

OK - on the question of vapor barriers and proper placement.

If drywall is being applied directly to block (or a concrete foundation) then no vapor barrier is required.

As a back up I would suggest the installation of a combination vapor barrier and mold resistant paint for the walls.

This is available as a finish product or as a primer/sizing for wallpaper applications.

This effectively locks the vapor into the room.

Any vapor which might migrate through the block (or concrete) from the exterior would meet a surface slightly warmer than the concrete itself (and hence the temperature of the moisture itself) and would not be able to make "dew point" and condense.

All of this assumes that there are no active water problems related to the foundation - and that there is not excessive moisture within the basement itself.

If the relative humidity is high in the basement - it can migrate along the foundation and still cause problems with mold - and thus would require the use of a dehumidifier to maintain proper humidity levels.

Reccomended humidity levels should not exceed 45% maximum and if at all possible 40% for extended periods of time.

I personally reccomend that levels be maintained between 35 and 40% - if you have a piano in the space (which requires 43% for the soundboard) this can be acheived with a humidifier made to install within the sound board itself.

If this opens the doors for more questions please feel free to ask away.

I'm sort of busy right now - so if i don't answer right away please send me an email to give me a nudge.

Sincerely,

Rod

[knightfly]

Cool, Rod, thanks a lot - looks like I'm understanding this part a LOT better, slightly different wording to say essentially the same thing - guess there's hope for me after all Steve

[z60611]

Knightfly
"Noise Control In Buildings" by Cyril M. Harris, apendix 5.2, has about 60 constructions with TL numbers involving masonry/concrete. It is the best source I've come across for these thus far for concrete block TL numbers.

However, much to my surprise, not one of them has two layers of gypsum, the way ALL of your pictures do.

Nevertheless, I'll quote one of the 60 here:

Description: 8" (190mm) concrete block [48lb/ft^2 (236 kg/m^2)], 1.5" (38mm) wood studs, 1.5" (38mm) fiberglass batts, 5/8" (16mm) gypsum board

STC: 55, Rw 55
63hz 32
80hz 29
100hz 29
125hz 37
160hz 42
200hz 49
250hz 48
315hz 47
400hz 49
500hz 50
630hz 52
800hz 55
1000hz 57
1250hz 60
1600hz 62
2000hz 61
2500hz 58
3150hz 61
4000hz 66

test lab: NRCC

[knightfly]

Thanks Bob; looking at those #'s, I'd say the single layer of gyspum with that air space makes a mild damped panel trap effect (worse TL @ m-a-m) at around 90 hZ... Steve

[musicman74]

Hello again,
I've been kind of busy and havent been able to do much with the project lately. I have managed to get the ceiling underway. After discovering and correcting a few junction boxes hidden above the ceiling tiles and running a few wires, i have filled between the joists w/ roxul (full fill,slightly bulged to dampen panels).
Before I hang the r/c and drywall up there I still need to figure out what to do about these damn block walls. Steve and Rod's posts were very informative(thank you very much ) but I'm still a little confused.
Upon further investigation, the outer block wall appears to be filled/solid. I only assumed this because upon looking at the top row the cavities seem to be full of morter(the joists rest directly on the block, is this normal?).It seems unlikey that they would be filled and I dont want to make a 3 leaf wall. The house was built in the late 50's, is it common to fill the block other than for special reasons such as sound isolation?
My two options are:
1-hollow block wall:
remove the furring strips, paint the block and glue 2 layers of 5/8 wallboard up.
2-solid block wall:
leave furring strips up, add unfaced insulation(703 or roxul?), vapor barrier then 2 layers of 5/8 wallboard on rc.
Does this sound correct? Would it be safe to just assume the block is hollow and glue directly onto it?
Steve, Iknow you said to ditch the paneling but I'm cheap and hate to see it go to waste. Is there any way to use it as a vapor barrier?I know this may seem half baked but maybe paint the finished surface w/vaporlock paint and face it towards the block?
Also, the other block wall is an interior load wall. does a vapor barrier apply here as well? This wall appears to be hollow.
Once the walls are up I plan on doing surface mount for the audio cables as to facilitate removal if I sell the house. As for the HVAC I have one outlet w/2 90 degree bends going into the room. The duct is 6" aluminum, would the fiber glass flex duct be better? I've also seen these insulated air outlets at home depot, would they be helpful here?Do I need an intake in the room? Man there sure is alot that goes into this. Sorry for adding more questions to my post, but you guys have been extremely helpful!
Thank you again for your time.
Keith

[sharward]

Steve, Iknow you said to ditch the paneling but I'm cheap and hate to see it go to waste. Is there any way to use it as a vapor barrier?I know this may seem half baked but maybe paint the finished surface w/vaporlock paint and face it towards the block?

Seems to me like an awful lot of trouble (and expense, for the paint) to go through to salvage paneling and avoid using plastic...

Gold plated paneling maybe?

[musicman74]

Sharward:
Point well taken
I was thinking in terms of extra mass,different thicknesses etc. But I think I'll spare myself the trouble and just hang the drywall.
Keith

[knightfly]

the outer block wall appears to be filled/solid. I only assumed this because upon looking at the top row the cavities seem to be full of morter(the joists rest directly on the block, is this normal?).It seems unlikey that they would be filled and I dont want to make a 3 leaf wall. The house was built in the late 50's, is it common to fill the block other than for special reasons such as sound isolation?

The top blocks would be filled regardless, so they don't leave the wall cavities open to the framing sill plate. Whether the rest of the cavities were filled is open for debate. That far back, someone might have actually cared enough to fill them for no reason other than it's stronger. Hollow blocks just mortared together are kind of weak as far as shear strength is concerned, so they might be. The only way I know of to be sure, is to take a masonry drill and put a hole in one of the blocks about 4" away from a vertical seam - if you hit air, you'll know.

Either way, you can stuff the hole full of concrete Fixall and smooth it over. If the blocks are earth-filled on the other side, it won't make a lot of difference because the heavy mass of earth will compensate for the "three-leaf" effect quite a bit if not totally IMO...

I think in this case that the least BS way to do those walls is glue two layers of wallboard to them, mud/tape/texture/paint (latex paint, NOT oil base) -

if the blocks are hollow, you won't have a 3-leaf wall.

If they're solid, you'll have a "mass law" wall.

Hollow block without extra mass is about STC 48, add two layers of gypsum and you're around STC 52-54, with a better bottom end than some walls simply because of the added earth mass.

IF they're solid, then it's straight mass law, and you're looking at about STC 60 with about 34 dB TL @ 50 hZ, and that's BEFORE you add the gypsum. With two layers of 5/8, you'd see about only 1-2 dB improvement across the frequency range.

One problem with re-using your paneling is possible rattles - unless you glue it solid, it WILL rattle. It's also not much mass for so much trouble. I'd give it to a homeless person to sleep under...

Also, the other block wall is an interior load wall. does a vapor barrier apply here as well?

Probably not. If both sides of the wall are at about the same temperature, then no barrier is needed. If it's hollow, you won't have a lot of isolation from it, around 46-48 like the other one. Adding gypsum to both sides won't add much, because of the mass that's already there. If you want a lot of isolation on that wall, you'll need to find a way to fill all the cavities with sand and add a separate frame and two layers of gyp with insulation between.

HVAC - you'll need both an inlet and an outlet if you want to breath without fanning the door. Flex duct tends to kink, but would be better than the aluminum for sound. IF you can run the flex so it does at least a total of 180 degrees of turn without kinking, that will work. Choose the largest diameter you can fit, and adapt your existing vents UP in size to it keeping the connection FLEXIBLE in whatever way you can (no hard contact with the rest of the HVAC system.

Going up in size will reduce the air velocity; noise generated by moving air is proportional to somewhere between the 4th and 5th POWER of the velocity, so a larger size will make a noticeable improvement in quiet.

Try NOT to have either duct dump into your room between you and your speakers; this will cause some wierd phasing problems due to dissimilar air temps and speed of sound varying.

I'm not sure what insulated air ducts you're talking about, if you had a pic or a link it would help... Steve