Stairwell framing

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emkays
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Location: Toronto, ON, Canada

Stairwell framing

Post by emkays »

I'm hoping someone has some time to share advice on approaches to framing/drywalling a stairwell so that it can function well as the second "leaf" of an isolation assembly. Pardon the crude and very rudimentary diagram/description, but hopefully it helps to describe the space I have. I just want to get my head around the possibilities before the framers finish the stairwell assembly component in this space.

A brief description:
- red: concrete foundation walls below grade
- blue: rough indication of intended mix room
- green: is the envelope that needs to be built around the stairwell area. This area includes the framing for the stairs themselves and the (unindicated) walls necessary finish the interior of the stairwell.

The specific area I'm curious about is:
- I'd like to avoid making this a multiple leaf assembly. Between the a) mix room, b) stairwell area c) interior walls that would enclose the stairs from the inside. Though perhaps that concern is an unnecessary concern given the open nature of the rest of the stairwell area. I'm mostly concerned with affecting the efficacy of transmission of the walls near the stairs.
- the structural assembly supporting the stairs itself has not been confirmed yet. So perhaps that should be treated a completely separated assembly and not worry that this adds an extra "leaf".
- the part that's confusing is how to address closing off the stairwell from the inside (aesthetically but also for safety) but also accommodating an uninterrupted massive wall assembly of the whole stairwell area. The simplest approach would be to drywall the exterior of the stairwell envelop, but then I'm not sure how I would address the area where the wall framing connects with the stair framing.

Sorry that this is so open ended. I've drawn up all sorts of possible framing options, but there are so many possibilities I'm curious if I should look at this with an entirely fresh perspective with any suggestions I can get here.

Thanks everyone for helping me wrap my head around this.
emkays
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Joined: Fri Apr 03, 2015 10:46 am
Location: Toronto, ON, Canada

Re: Stairwell framing

Post by emkays »

Happy holidays everyone and anyone celebrating this time of year.

It's getting close to this part of the main building being framed and I wanted to post with my thoughts and perhaps a more specific question or two. In reference to the image attached which reflects one corner of the green wall assembly of the original post.

This first diagram shows a dual stud framing assembly with some options indicated. The stairwell being on the residential side, and the blue drywall being on the eventual studio side. At this early stage, I just don't want to make any bad decisions with the framing of the residential side. My main point of confusion comes from how to handle the potential three leaf scenario that's indicated here. The green drywall would be in place to enclose the staircase from the inside. This large spiraling stair case uses the framing as part it's structural assembly. My (hopefully incorrect) assumption is that this will leave it with many penetrations and that it only serves an aesthetic/safety purpose as seen from the stairwell side. Even if constructed with spacing between the stair stringers and the framing. Necessitating one of the following solutions.

So my thoughts/hopes are:
- I'm completely wrong about how the green leaf is constructed and that it can indeed be made more massive/sealed from the stairwell side. Obviously and ideally eliminating the red leaf. Ending up with the more ideal assembly in the second attachment.
- Or that I might have to add mass to the green leaf from the other side of the wall, between the studs. This one sounds laborious and wrong in various ways, but wanted to mention it anyways.
- Or that the red leaf is an acceptable compromise since the inner green leaf isn't relatively significant enough given my assumptions above.

Also, if I can figure out a way to make a good two leaf 'Green' and 'Blue' assembly, I'm also left with the third attachment: how to handle framing that interrupts the Green leaf.

Any thoughts on the above would be appreciated.
DanDan
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Re: Stairwell framing

Post by DanDan »

Well done on the sketching and effort you are putting into this. But I am struggling to distill a question.
You have three sketches in the last post. The first looks as difficult to actually do as an 'inside out wall' And it has 3 leaves.
The second looks like normal independent studded MAM partition walling. It can be readily enhanced by increasing any of the three elements.
emkays
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Joined: Fri Apr 03, 2015 10:46 am
Location: Toronto, ON, Canada

Re: Stairwell framing

Post by emkays »

Hi DanDan. Thanks for replying. Sorry my yammering has veiled the actual question ;) It's a bit difficult to describe the problem I'm trying to solve and I'll try again.

I guess my question is: which of those thoughts are the likely correct approach given the specific details of the stairs impacting the ability to seal the inner green leaf? The core of the conundrum being that the stair side will likely be difficult to drywall without many penetrations caused by it's need for structural connection to the framing. This is the part I don't quite know how to handle. So, more simply:
1) attempt to create a proper sealed leaf on the stairwell side as best as possible. The diagram is labelled 'Ideal assemby'. Realizing however that even with a space between the stair stringers and the framing, there will be many structural penetrations that will need to be somehow addressed. The main crux of this is that I fear that that they cannot be adequately addressed. Resulting in the next thought.
2) build a "sort of" three-leaf assembly in the first diagram. Assuming that the inner green leaf is of a traditional/light/unsealed construction. Perhaps partially negating it's negative impacts. Ultimately resulting in better isolation than #1 since the red leaf can be constructed as a much more sealed leaf.

To clarify what I clearly poorly labelled:
- only the first two images refer to potential solutions to the scenario.
- the third is a secondary question that stems from going with the one labelled "ideal assembly". We can ignore that one for now since there are a few logical solutions there. I was mostly curious what others would do on this one.

Thanks for taking the time to read this and hopefully my second description is better this time around. My gut tells me that I'm wrong about not being able to adequately seal the structural penetrations and that it remains the better route, but I'd love to hear from others.
gullfo
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Re: Stairwell framing

Post by gullfo »

depending on the volume levels and frequencies, the structural transfer is going to become the loudest sound levels passed. so using the "ideal assembly" should be used and consider either a third drywall layer or a viscoelastic layer between the two.

on the "interruption" side - consider changing how the walls butt, (presuming the perpendicular wall is not a support wall for the isolation wall), to each other to carry the drywall (isolation drywall) across to complete as much sealed mass space as possible. the fasteners should not have air penetration since you'll be alternating the layers and staggering the screws as well as sealing each layer, those should not be a problem. :-)
Last edited by gullfo on Tue Dec 29, 2020 10:35 am, edited 1 time in total.
Reason: some missed words
Glenn
emkays
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Re: Stairwell framing

Post by emkays »

Thanks Glenn. Great points and I appreciate your thoughts pointing me in a good direction! I think "ideal assembly" is best and I'll talk to the stair contractor. My worries stem from the fact that I've never built such a big stairwell that ties into such a system. I just want to make sure that I can seal well enough around the structural elements that connect the stairs to the framing.

And yes, I still have a chance to change the framing design of the "interruption". That's the ideal solution there!
gullfo
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Re: Stairwell framing

Post by gullfo »

if it's not already built, consider doing some things to keep the stairs from be directly attached to the isolation walls as this can reduce the structural transfers - think isolation bracing to reduce the contact on the side walls.
Glenn
DanDan
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Re: Stairwell framing

Post by DanDan »

The structure borne sound from the stairs will be strong. You need a stand alone stairs.
emkays
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Joined: Fri Apr 03, 2015 10:46 am
Location: Toronto, ON, Canada

Re: Stairwell framing

Post by emkays »

Appreciate the direction towards looking at structural borne implications. Luckily, use of the stairs is very limited during critical times. Of course, as always, there are many other considerations when things are tied to a residential build. This one has a particularly long and difficult story. I should be hearing from the stair contractor though soon with an idea of the design they had in mind. It definitely won't have any consideration for isolation but I'll take it from there. It's a big 4-landing stair case to get down 16'...eep. Looks like I might be in for a bit of a puzzle and I'll share back my thoughts here. Hopefully there will be some patient readers left ;)

I had initially thought of creating an isolated isolation framing around the stairwell area as well. Thanks for the suggestion. Something I had forgotten to go back and play with until your comments. Not sure the realities of the space will allow that, but I'll add that to the list of "sketchup variations" to explore over the next few days.

I appreciate the posts
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