Second floor studio questions

  • Thread starter Thread starter WagTheDog
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By "surface bonded," I think Steve is referring to the method of laying concrete blocks dry, and coating the wall inside and out with a slurry that, where I have seen it, includes resin and chopped fiberglass. Because there are no mortar joints to compress or fracture, it's supposed to be stronger and more stable; and maybe it is better from a sound isolation standpoint, too.

But, Steve, back to what WagTheDog and I were discussing (well, speculating about), what are your thoughts about adding mass to a floor above a garage, assuming that it is not floated? What do you think of Wag's ideas for materials?
 
I've got my space in a bonus room above a garage also. Rather than adding mass to the floor, the issue seems more to be that the SPAN of the garage (20+ feet) make the floor like a drumhead. I would suggest adding some jackscrews in the garage space between the car stalls under the support beams to cut the length of the span. If you cant isolate the floor from the garage, then work on isolating the garage from the outside. Blow insulation into the garage walls. Insulate the overhead doors. Curtain the windows. Make the garage "dead"...let it be a sound trap.
Ive got a 12/12 slope on the outer roof. I built closets along the outer walls 3' deep, and insulated the outer wall and the closet wall, with a 3' dead air space in the closet ( well, not really dead air space..theyre full of sh**, but you get the idea). The ceiling is just insulaled to the max between the outer roof and the sheetrock. I learned that second floors and especially slope roof attics/bonus rooms make difficult places for studios, but we dont have basements here.
 
I have a 2X16 joist that runs down the middle of my garage (the dotted red lines are the joists):

studio_joists.jpg



So my maximum span is about 7.5' on the 2X12 joists going across.
 
Is the 2x16 joist support in one or more places along its run, or just at the ends? You'd be amazed at how much deflection you get across that span.

If you dont have any added posts in the garage, that is by definition a clear span and will exhibit vertical movement. Jump up and down on the floor upstairs...you will feel it move.
 
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You mean what does the 2X16 joist sit on? One side is on an exterior wall, the other is on the interior garage wall. Here is a pic of when the house was being built....
joists1.jpg
 
"By "surface bonded," I think Steve is referring to the method of laying concrete blocks dry, and coating the wall inside and out with a slurry that, where I have seen it, includes resin and chopped fiberglass. Because there are no mortar joints to compress or fracture, it's supposed to be stronger and more stable; and maybe it is better from a sound isolation standpoint, too."

Exactly; do a google search on surface bonded block and one on dry stack block, there are a few pages with pix and explanations. By filling all the cavities that aren't already filled with mortar (for strength purposes) with SAND, you make that block wall into a SINGLE leaf of mass that's well-damped. Then the inner gypsum on studs (and the air gap between) along with the mass of the outer leaf, make up your mass-air-mass construct. Wider gap and more mass help lower resonance to below audibility... Steve
 
Thanks for the cross-reference to the "other" thread. I have been mining John's site for a while now, trying to plan for my own over-the-garage space, and that's a helpful addition to what I have found so far on "attic" studios. Two points that haven't really been resolved yet in that thread are (a) should he build a floated floor and (b) the fact that the garage roof has continuous soffit vents.

As to (a), there has been much discussion about the weight issue but not Rod's point about the probably poor isolation value. Apart from being a drum head, it also looks like it would be a third leaf (since there is a ceiling in the garage below). Steve has made a suggestion about adding additional material to the existing floor which seems like the best way to go.

As to (b), the soffit vents mean that the air space between the outer (roof) leaf and the inner (single new wall) leaf will not be sealed, which technically blows (!) the whole M-A-M system. Presumably that venting is still needed. Hasn't Rod recommended that, in such cases, it is better to build a new "inner outer leaf," e.g. sheetrock on the inner face of the rafters, then an inner leaf separate from that? Then Wag's original idea of a two-leaf knee wall would also be appropriate.

I don't mean to confuse the issues, but I am faced with the same decision. Perhaps I should raise these questions in the "other" thread.
 
Ok, I see the structure, and it confirms what I am thinking.
Think of that upstairs floor as a drumhead. if you press your finger down on the middle of a drumhead, what happens?? You dampen the sound, and by cutting the length of the span, you increase the frequency at which the floor will resonate. It takes a lot more energy at higher frequencies to make that floor move (transmit sound) than at a lower frequency. This is a gross simplification of the principle. Its just a simple way of stiffening (??) the floor and reducing unwanted vibration.

BTW my biggest sound hit is when my son comes ho,me and hits the garage door opener button.......that fu**ing motor is mounted to the underside of MY floor (drumhead)!!
 
I decided not to go with a floated floor.....I'm thinking now that I will put down a bunch of Green Glue on top of the existing floor and add a layer of MDF. I'll also have a QuietPad over that and then a layer of 6mm laminate flooring.

I need to take a more recent picture of the studio build....I'll do that this weekend.....the soffit holes are covered up with a couple of layers of MDF and insulation.

Floating a floor would add a third leaf.....garage roof/plywood flooring/floated floor. That's the main reason I'm just going to add more mass to the existing floor.


P.S. Techno, I have the same problem...the garage door opener....I put some rubber washers on the hanger braces to deaden it, but with limited success.
 
Ah, okay, that answers the soffit vent question, in your case. I am uneasy about blocking them, since inside my roof it gets pretty warm in the Summer, and there can be a lot of condensation in the Winter. I guess the condensation wouldn't be an issue if the inner leaf is a vapor barrier, though.

That seems like the way to go for the floor.

And maybe the "kill" switch on the garage door opener is the only answer for that. Besides, keeping the garage doors closed may help with isolation - I'd kill not only the remote control but also the wired control (our cars stay in the driveway all the time, anyway -- too much other stuff in the garage).
 
Well, the insulation and MDF is not sitting right down on the soffit holes....the MDF is level with the plywood floor so it's 12" from MDF to soffit board. There is about 6" of gap between insulation and soffit holes. Air will still come up thru the soffit holes, it will just travel down the soffit board until it finds an opening into the attic. The insulation I'm using is 6.25" 23"X93" Owens-Corning R-19 unfaced (W-61). It gets hot here too, about 100 in summer but not too bad in the winter....we get maybe 3 snows a year, a couple of hard freezes for a few days.

Right now I'm trying to figure out what to do about the studio doors....whether to make one big door or do the double-door thing....leaning towards the double-door solid core.
 
Went to Lowes yesterday to look at doors....they didn't have any solid-core prehungs....called them again a few minutes ago and now they have some.....Reliabilt ....only 1 3/8" but solid pine.

My question is, do I need 2 doors or one, going into the studio? I already have a door going into the actual "attic" area......here is a diagram:



Here is an actual pic:





The distance between the doors (the center on each) is about 4'.....should I double up where I have "New door" in the diagram or would 1 door work? The existing door is a 32" with weatherstripping.
 
Better if you can do something more like this; notice that the change gives you a continuous outer leaf of mass that includes your existing door, and a continuous INNER leaf of mass that is NOT connected to your outer leaf? It also gives you a vestibule (sound lock) that's large enough to move gear in and out of without fighting two doors at the same time. Some good seals on the doors and some absorption material in the sound lock, and it won't be your weak link... Steve
 

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Steve,

When you are referring to the inner leaf not connected to the outer leaf...just want to make sure I'm understanding this correctly.....I'll use the west wall as an example.....from inside out.....I'll be putting up 2 layers of 5/8" sheetrock onto the 2X6 joists that run at about a 45 degree angle, then insulation, then I have roof sheathing, then roofing paper, then shingles.....the outer leaf and inner leaf will therefore be sharing a common stud (the joists)......am I messing up there? It would be difficult to do it any other way.
Here is a sideview looking north....the thick brown lines are a sideview of the joists, the blue lines are the sheetrock to be attached.
sideview0708.jpg


Here is a more accurate view, taking your attachment......the east wall is further away from the inner leaf kneewall than I have been drawing.
studio_layout_0708.jpg


Thanks for your help!


P.S. Rick, if you find the answer to your "problem", let me know......I have a terminal case of it myself.
 
im pretty sure the lowes in your area will also carry 'solid' luaun doors... ie they look like hollow dorrs but are solid filled with mdf... = lots of mass ... and no pine panels to rattle in their frames..

but pine looks a hella lot better

also, after looking at your picture they make solid doors that are stamped mdf.. that look like the one in your existing wall..

gl
 
Wag, since there are only your roof rafters and wall studs carrying both your inner and outer leaves in most places, perhaps you ought to hang your sheetrock on RC (resilient channel).
 
Wag, since there are only your roof rafters and wall studs carrying both your inner and outer leaves in most places, perhaps you ought to hang your sheetrock on RC (resilient channel).
Click to expand...
I agree. Your plan kind of fools people. Going just by the plan, double walls makes sense but the section and pics shows a very different aspect, being there are NO walls on one side, just roofing rafters, no?. It would be difficult at best to suspend a decoupled cieling from the rafters using ANOTHER set of rafters for a total room within a room type affair. RC offers easy decoupling in this application I believe. Or, if budget allows, maybe Risc clips/hat channel perhaps. Whatever, I would at least use RC.
Two other ideas as well. If your isolation goal warrants it, and If the rafter dims and spans allow it, you could beef up the roof leaf by adding a layer or two of drywall BETWEEN the rafters, right up against the roof shiething. Use 50% application of Green Glue between the roof shiething and the first layer of drywall and between two layers of drywall for the best benefit of multiple layers acting as one. Two 1/2" layers will act as ONE layer of 1" from my understanding. Same with the layers mounted to RC, although I would have the span/rafter weight calcs checked. I may be totally outta the ballpark with this one. Steve or Rod will probably have something to say about this as well. Reason is, my status as an expert is borderline novice when it comes to structural. For that reason, my disclaimer is always in full force when it comes to structural/acoustical advice...ie....I ain't no expert. ;)

PS, you might also consider a ROLLOUT fiberglass/puck product for the floating floor aspect. It might just be the ticket. Again, the disclaimer rules.
 
Sorry.....I'm really not trying to "fool" anybody. Just bad drawings I guess.

Yes, on the west wall it is nothing but the roofing rafters. Same on the east wall until it meets the knee-wall. The north wall that I will build will be a separate wall, same with the south wall. The existing north wall has a window and is of course an outside wall. The south wall is an existing window and I'll build another wall parallel to it too....on the other side of the south wall is a bedroom.

I agree it would be next to impossible to have a true room-within-a-room in my situation.

Are you saying do RC on the west and east walls or all the walls? If I went with adding a couple of 1/2" drywall between the rafters (glued onto the sheathing), would I still use RC on them? I know the RC is for decoupling, but would adding the extra mass to the roof sheathing give enough STC to make RC unnecessary? I was thinking that any sound escaping from the roof would be hard to hear on the ground since it would be so high up, so I wasn't that concerned about it. I am more concerned with the south wall and the floor. Am I thinking wrong?

What exactly are you talking about on the "ROLLOUT fiberglass/puck" flooring? At first I was going to float the floor, but seems like it would create a third leaf.....leaf 1 being the garage ceiling, leaf 2 being the thick plywood floor. If I put pucks on the existing plywood and then a layer of MDF on top of the pucks, wouldn't that be a third leaf?

Thanks for you guys help, I appreciate it.
 
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