The interior of exterior walls

Sword9 · Post by **Sword9** » Sat May 21, 2005 5:12 pm

I'm wondering what is the best construction method to use to "finish" exterior walls in a two wall system which are also exposed to the inside. For instance, in a hallway. See the picture below of the closeup of my design. The flat black line underneath the 13.5 is an outside perimeter wall. In this instance, it'll be a wood shingled outside wall with a layer or three of wooden wall board and some insulation between the studs. On one side is the outside world, on the inside is the studios. In some places there is inches between this wall and a studio wall, but in other places like this hallway, the inside portion of the wall is exposed to the "public" as they walk down the hall.

How do I finish the inside of the wall (where the insulation will be exposed) without creating a 3 or even 4 leaf system when it's up against the other rooms? Also, how do I seal the ceiling in my outer room within a room without cutting a lot of chunks out of my gypsum to make a good seal with the outer walls and still fit between the studs?

Sword9 · Post by **Sword9** » Mon May 23, 2005 9:27 pm

would fabric over these areas be okay if I had some sort of mesh installed to hold my insulation in place?

Deluks · Post by **Deluks** » Wed May 25, 2005 11:28 am

Can't you continue the wall in the top right (in green) using the same construction?

(I'm assuming the red line is fabric covering over insulation, if not then you already have a have a 3 leaf system right there)

I think the width of the walkway/hallway would be enough for 4 leaf to not be a major problem, some photos would help.

Sword9 · Post by **Sword9** » Wed May 25, 2005 10:34 pm

well here's the whole plan for perspective.

In thinking about it more, I guess the best way to do my outer shell is to make the walls be "inside out" type walls. I'm just a little worried about how much extra work and trouble notching my ceiling around the studs is going to be to make an airtight room. Not to mention all the 16" wide strips of gypsum I'll have to cut to go between studs.

The other pic is of my current inside-out plan(although the shingles and outer wall board part is not so set in stone, since I don't know exactly what the neighborhood will need to make it look like the other buildings.)

Thanks for anybody taking a look.

(edit: I've redone my wall design. Hopefully it is more readable and looks better.)

(edit #2: old inside/out wall design deleted as it was horribly flawed.)

Sword9 · Post by **Sword9** » Sun May 29, 2005 1:00 pm

So I've just learned that my friend is building the studio to match his house and thus the construction is different than what I thought it was going to be. Instead of going cedar siding, exterior wood wallboard, then studs and interior finish, the construction is going to be cedar siding, styrofoam board, studs. I'm wondering if I do the construction I'm proposing for my outer shell (which is the thick black line making up the entire exterior of the building) would I be creating a multiple leaf situation that is bad? Or is the styrofoam and siding letting enough air pass to not qualify as mass?

Then my other question is, will it really matter? I'm planning on two layers of gypsum on this outer wall and ceiling and 3 layers (of varying thickness) on all interior studio walls and ceiling. Thanks for any ideas/suggestions.

knightfly · Post by **knightfly** » Mon May 30, 2005 9:10 pm

Sam, styrofoam is closed cell so won't act as an "air" space; however, it's also WIMPY as mass, and thin siding or shingles won't help much as far as acting as the outer leaf of a mass-air-mass wall - adding a couple layers of wallboard between studs will help some, but where each stud is located the only mass would be a small amount (siding) and an even smaller amount (styro) - so I'm not sure how well just adding inserts BETWEEN studs will work.

Inside that, you show a single frame with both masses attached to the same frame; considering the puny aspects of the OUTER mass, that wall won't be much for isolation IMO. To help combat the wimpy outer leaf (even WITH two layers of gyp inserts) you would need separate frames and 2-3 MORE layers of gypsum with a total air gap from innermost insert to the first surface of the INNER gypsum of at least 10-12" - the deep air gap will help m-a-m resonance a fair amount, but a lot of that gain could be LOST if the outer covering provides air space (like shingles) -

Just some random thoughts... Steve

Sword9 · Post by **Sword9** » Mon May 30, 2005 10:02 pm

That picture is only the exterior wall. All inner studio/CR walls will be 3 layer gypsum with the frames at least 6" apart from facing studs to facing studs. In many places, the distance will be closer to 10-12 inches apart. These rooms will be on totally isolated different slabs of concrete too.

A couple of posts up, I posted the old proposed design of the exterior walls and the actual floorplan that I'm currently going working on (some slight modifications are always happening, but it's pretty current.) The thick black line that makes up the outer 34'x42' rectangle is the wall(s) that this question is about. I'm going to remove the original inside/out wall example just so I can try to avoid confusion. The Ceiling of the outer shell will also be two layer with 3-4" insulation behind it like the exterior walls.

thanks.

knightfly · Post by **knightfly** » Tue May 31, 2005 6:02 am

Sam, sorry but I need more detail on this to be sure; I've marked your plan with what I need - just pretend that I will be the builder, that YOU won't be there to supervise, and that you want it EXACTLY right. Then draw a sketch labeling each and every layer from one side to the other, roughly to scale - include actual measurements.

The problem is, everyone describes things differently; to some, a 3-layer wall means one frame, 3 layers on one side; to others, it could mean one layer on one side, two on the other - to still others, it could mean a double frame with one layer on one frame, two layers on the other.

If you draw a sketch, I don't have to rely on what I THINK you mean... Steve

Sorry, forgot to attach the markup; here 'tiz -

Sword9 · Post by **Sword9** » Tue May 31, 2005 8:49 am

Sorry for all the confusion. Once I really get stuff sorted out, I have a CAD guy we're hiring to do the blueprints, specifically because drawing is clearly not my thing.

Hopefully this image will help clear this up.

So I guess right now my wall will be a Mass-Air-Mass-Air wall, since I've had to flip the position of the insulation between the studs on the exterior wall. So the construction will be(from top of drawing to bottom of drawing): "B" Gypsum(5/8",1/2",5/8") 3 layers, Insulation between studs, minumum 6" air gap(from studs of A to drywall of B) but often greater distance, "A" Gypsum(5/8", 1/2") 2 layers, Insulation between studs, styro board, shingles.

thanks.

Thanks.

knightfly · Post by **knightfly** » Tue May 31, 2005 3:13 pm

Sam, the top drawing is what I think you mean to do; the middle one is what I would do INSTEAD; and the bottom one is WHY -

I'm running behind as usual, if I left anything out just yell... Steve

Sword9 · Post by **Sword9** » Tue May 31, 2005 10:05 pm

Thanks for calculations Steve. You are correct. Your layout in drawing one is exactly what I was hoping to get away with. Although it adds quite a bit more labor costs, your second drawing seems to be the way I'll have to go. I do have some construction questions though.

How do you affix the gypsum between the studs? Do you just angle the screws into the studs, or will I need some kinds of brackets? I'm sure of the caulking and sealing, just wasn't so certain on the actual screw schedule.

My second question is, given my current plans, what'd be the best way to lower the resonance and improve my STC with your suggested construction? Would it be a 3rd layer of gypsum or MDF or some other wall covering? This design is out in the country and there is a reasonably good distance between the studio and any neighbors. I'm not incredibly worried about that low end sound getting out, since the distance will help greatly, however the passing tractor or car could be trouble in the other direction.

Third and last question, How do I do the ceiling of the outer shell now? Will I have to notch out rectangles in my gypsum to slide in between the studs and butt up against my gypsum that'll be in between the studs to achieve an airtight room?

Thanks for the help, and thanks again for crunching the numbers.

Sword9 · Post by **Sword9** » Sun Jun 26, 2005 8:19 am

I'm still having a hard time figuring out how to secure the gypsum between studs. I'm pretty sure that you can't angle in screws or nails, since you'd just have powder when pressure is put on it.

Do I put up cross bracing between studs and run screws through those? Or is there some sort of bracket made for this? I'm sort of at a loss on this technique I guess.

Post by **sharward** » Sun Jun 26, 2005 2:41 pm

See this thread -- it covers it really well.

Sword9 · Post by **Sword9** » Sun Jun 26, 2005 8:03 pm

None of those solutions really seem to be cost/labor effective for the more than 1600 sq ft of walls this method needs to work on. Plus, I don't have a subfloor to screw into.

I'm beginning to wonder if I should just put my drywall on the exterior like I had once planned, and fill the walls with sand. The studs probably wouldn't support that though.

knightfly · Post by **knightfly** » Tue Jun 28, 2005 5:41 am

Sam, is there a pic up of your roof design - gable, hip, mansard, flat, ?? And, is this building already existing or all new construction as it sounds like? Thanks... Steve