Aaron's "studio" build

Neat ! Looking good! I like the way you built both frames at once, without putting any walls or roof on either of them, so you have access to everything while it is going up. Good idea.

Sweet! Inspector gave the go ahead for the sheathing and roofing to begin.

ajoantmug wrote:

We didn't bob the joist tails as this box will be sheathed in 2 layers of osb, then there will be a plate placed around the perimeter of the top of the box for the rafters to be placed on with a bird mouth cut.

I guess as long as you have weighed the three leaf factor into this roof assembly, sounds good and strong!

Xspace, this has been my biggest concern from the get go. I looked into doing a flat roof, basically just having a box in a box, but was strongly encouraged not to do this by roofers. Here is what I know: a) my box in a box will be a very sound structure for isolation b) my roof will be coupled to the exterior "box" via the rafter plate (Nailed through the sheathing and into the exterior ceiling joists. What I don't know: a) how much will this roof design limit the isolation of the structure as a whole b) does the amount of open space in the attic area limit the negative effects of having the roof coupled to the exterior box c) would putting green glue between the rafter plate and the sheathing have any positive benefit. My first post has a picture of how this is tied together. (the picture shows a fan, but I have since decided to go with a ridge vent so that there are no holes through either box). Any advice?

a) how much will this roof design limit the isolation of the structure as a whole

It will be your weak point for low frequency isolation. Three leaf reduces isolation greatly at the low end.

b) does the amount of open space in the attic area limit the negative effects of having the roof coupled to the exterior box

Not really.

c) would putting green glue between the rafter plate and the sheathing have any positive benefit.

Nope. - Stuart -

Thinking out loud here, well in writing: Though it is coupled, wouldn't the fact that there will be an air gap on two of the roof sides where the rafters come down to the plate and at the ridge vent mean that this is not a sealed space so it would not have as negative an impact as a sealed attic? Aaron

I haven't completely figured out the "how much three leaf is too much". But I do know it is done a lot. It is one of those areas you live with what you have. I am of the mind that your two leaf ceiling, if I understand what I am saying:), will have enough mass to overcome some of the three leaf effect of the roof/3rd leaf. There again, how much, I haven't retained that information. But, the three leaf is in the top most part of the structure. It should not alter the walls ability to isolate as planned. For getting the most overall isolation from the exterior...what you are doing is probably the best method. When you pop a roof on there(as a two leaf), run soffit, ridge and gable end vents, you have so many holes that the loss in TL from your current three leaf is better then the loss of pure isolation from a two leaf. Make sense?

Though it is coupled, wouldn't the fact that there will be an air gap on two of the roof sides where the rafters come down to the plate and at the ridge vent mean that this is not a sealed space so it would not have as negative an impact as a sealed attic?

Not really. It doesn't need to be sealed in order to act as a third leaf. The "sealed or not sealed" issue only affects the TL frequency curve, but a leaf that isn't sealed is still a leaf. That said, Brien is right: You have to live with what you have. I think I'd run the numbers to see if this is even going to be a problem for you. Maybe it doesn't even matter. But you'll never know unless you figure things out. Best case, you might not have to do anything. Worst case, if it is a huge issue, you can always re-design the roof. After all at this point all you'd have to change is a few dozen bits of wood! Sad, but not the end of the world. It would be MUCH sadder if you didn't check the numbers, then carried on building and only find out when you are finished that it didn't work too well! Hopefully it won't come to that, but spending a few minutes figuring out the numbers might save you some big heartache down the line! - Stuart -

Ok, I am taking it all in. Trying to do the math. Thanks!

OK. let's see if I got this correct: Fc=c[(m1 + m2) / (m1m2d)]^.5 So, then: Fc= 43[(22.61625 [removed] / (22.61625 X 14.364375 X .254)] ^.5 Fc= 43[36.980625 / 82.516547] ^.5 Fc= 43[.44816]^.5 Fc= 43 X .669447 Fc=28.7862247 Ok, so now what? Someone please hold my hand and walk me through this. :oops:

Greetings Aaron, I was hoping you could share what you have come up with on your ceiling / roof. Thanks, Stay Gold, Ken Hamilton

Ken, Thanks for the inquiry, but notice you are the first to respond since my last post. aaron

It's not what I am comfortable doing, but, with the overhead two leaf having a resonant frequency of 29Hz, that's pretty low right?

xspace, based on my limited knowledge/understanding this is pretty low, but this figure is for the system as a whole (not including the roof structure). btw: what part are you not comfortable with? aaron

I'm not comfortable with explaining math:0 But, yes, I realize it is two sides of one assembly which is why I said what I said. This is where I don't know to what extent the third leaf effects it or how to mathematically represent that.

gotcha we're stuck in the same place, just 100's of miles apart!

Sheathing is almost finished. I'll post some pics when it is completely done--hopefully in the next day or two. I know this is a no-no, but I apparently missed the stud a couple of times when nailing the osb, resulting in the nail protruding in between the joists. Is there anything I should do about this? I have made sure that I did secure the sheathing in those couple areas. thanks, aaron

Greetings Friends, Hope this finds you all well. Thanks Very much for providing so much great information. If anyone could help Aaron with his equazion / math, Please don't hesitate a response. I know it would be much apreaciated. Thanks So Much, Again. Stay Gold, Ken Hamilton Aaron's math: OK. let's see if I got this correct: Fc=c[(m1 + m2) / (m1m2d)]^.5 So, then: Fc= 43[(22.61625 [removed] / (22.61625 X 14.364375 X .254)] ^.5 Fc= 43[36.980625 / 82.516547] ^.5 Fc= 43[.44816]^.5 Fc= 43 X .669447 Fc=28.7862247 Ok, so now what? Someone please hold my hand and walk me through this.

Greetings Aaron: Hope this finds you well. I am not sure, but check out this thread and see if it helps. Mybe a PM to the gentleman could get you some ideas, or answers to your ceiling???'s viewtopic.php?f=1&t=10239&start=0 Take Care, Thanks Again, Stay Gold, Ken Hamilton

Greetings Aaron, Hope this finds you well, viewtopic.php?f=11&t=7169 viewtopic.php?f=10&t=9156&start=120 Stay Gold, Ken Hamilton

Ken, it would help me a lot, maybe some others, if you could define where it is you are going with the links? I don't get the connection?

xSpace wrote:

Ken, it would help me a lot, maybe some others, if you could define where it is you are going with the links? I don't get the connection?

Greetings Brien, Hope this finds you well. I was thinking that the Oasis build showed a uniqe ceiling that maybe Aaron could reference and maybe provide some information that will ease his mind or give him an idea of how he wanted to proceed with his ceiling. The Lou's Studio Build, I thought was very informative and detailed on how he dealth with his uniqe ceiling and upscale build. Again, I was thinking maybe Aaron could see something that would help him in his build. I am very sorry I wasn't very clear with my posting, I reread what I posted and I can clearly see that I wasn't clear..... If Aaron is going to use his attic space for ducting and or wiring, I was wondering if maybe using that space for hanging absorbers and make use of the attic as more of an assect instead of as just a third leaf - problem...???? Thanks Again Brien Stay Gold, Ken Hamilton

"I can clearly see that I wasn't clear....." Mind if I use that sometime ;) 'Preciatte it Brien edit: To the third leaf. Although no one of any stature has said otherwise, with the 28Hz that he got from the entire top area assembly, I think it most likely will help ease the effect from the roof. It is still a 3rd leaf, but you live with what you have, right?

Well, it has been a while.....longer than I had hoped, but weather, work, and kids make finding time quite difficult. The gable end with the sheathing missing is for the inspector to get in. I hope to get shingles on starting today.

I don't want to start anything you can't finish, but how is it that you plan to vent this roof? Is it going to come up when the inspector shows or is this something you guys have already planned for?