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Basement Sill Plate soundproofing options
Old 2 weeks ago
  #1
Basement Sill Plate soundproofing options

Hey guys,
I'm in the midst of my basement room within a room build. My neighbors are getting a new roof installed and the contractors were walking by the side of my house while I was doing some prep work in the basement... and I could hear them talking as if they were in the next room. So I did what any builder would do... panic.
Is it normal for basement sill plates to let in/out so much sound? I've read Gervais' book several times before starting construction and I don't recall learning about a proper sill plate muffling technique. Will the two 5/8s drywall Im putting on my interior wall and ceiling be enough or can I do more?

Maybe drywall slabs hung vertically up against the sill plate between the floor joists??

Help.
Old 2 weeks ago
  #2
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Kyle P. Gushue's Avatar
Im not sure specifically which sill plate your referring to.

Rod depicts how to seal up the sill plate that rests on the foundation. This is what the house framing is built on.

If you look at the details for adding mass you will notice that the drywall between the ceiling joists, continues into the bay which is formed by the house walls, and floor joists. Directly above the sill plate.

If its the footer for the studio walls, then the drywall perimeter backer rod and caulking will seal it off. There is no need to seal the footer itself.
Old 2 weeks ago
  #3
Quote:
Originally Posted by Kyle P. Gushue View Post
Im not sure specifically which sill plate your referring to.

Rod depicts how to seal up the sill plate that rests on the foundation. This is what the house framing is built on.

If you look at the details for adding mass you will notice that the drywall between the ceiling joists, continues into the bay which is formed by the house walls, and floor joists. Directly above the sill plate.
We're on the same page. I'm referring to the sill plate that rests on the foundation, AND the end joist. The sound leaving my basement, currently, is very audible outside.

I sifted back through Rods book and found two pics that I believe you are referring to. Ive attached them to make sure we are referring to the same thing, as well as a pic of the cavity in my basement...

So, according to Rods first example, he is suggesting to pinch insulation between the sill plate and the concrete foundation, then seal with sealant. In his second example, he shows a 2x6 inserted perpendicular between the joists and the end joist, seated on top of a piece of drywall and sealed with backer rod and caulk.

There appears to be no gap between my concrete foundation and sill plate (as you can see in my pic) so I dont think the sound is getting through that way... I think its traveling through my end joist.

Would this be a possible solution?:
- Compress two pieces of R13, no more than 25%, into the cavity.
- Cover the cavity with a piece of 2x6 and seal the edges with all weather caulk or expanding foam.
- Attach 2 layers of 1/2" drywall with Green Glue

I should mention that I am creating an independently-framed ceiling, so none of my inner shell with be coming in contact with this area. I just want to cover all my bases.
Attached Thumbnails
Basement Sill Plate soundproofing options-img_0219.jpg   Basement Sill Plate soundproofing options-img_0220.jpg   Basement Sill Plate soundproofing options-img_1245.jpg  
Old 2 weeks ago
  #4
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Kyle P. Gushue's Avatar
You want to seal between the foundation and the sill plate, it is not airtight and it needs to be. Even a 1/32" of an inch 12ft long, is a significant hole if you turn it into sqft. Use the sealing method described in the book.

For the rim joist, (above the sill plate) refer to figure 10.9 (pg 258 on my kindle). Look at the added mass between the floor joists, and how it extends to the rim joist. Notice the seems are staggered where they meet.

The drywall in the pic you linked, is fire blocking. You need both, fire blocking, and the added mass to the rim joist, as well as a sealed sill plate.

The book doesn't include anything that isn't absolutely necessary, so the plans can and should be followed verbatim.
Old 2 weeks ago
  #5
Found it!!! OMG thank you

You know I dismissed this pic last time I read through the book b/c I figured it was describing only soundproofing the HVAC.

This is a lifesaver! Figure 10.9 for the win

And Kyle for pointing it out, of course!
Old 2 weeks ago
  #6
Hey Kyle, or Rod, or anyone,
In figure 10.9, where exactly does the thermafiber go? Does it rest between the firestop and inner wall header? Or....
Old 2 weeks ago
  #7
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Kyle P. Gushue's Avatar
Quote:
Originally Posted by JMillz.Perc View Post
Hey Kyle, or Rod, or anyone,
In figure 10.9, where exactly does the thermafiber go? Does it rest between the firestop and inner wall header? Or....
The thermofiber is between the header and firestop.

Keep in mind that assembly is using Channel for the ceiling, not an independently framed ceiling. The firestop details vary by assembly.
Old 2 weeks ago
  #8
I see I see. Im using Figure 4.28 as well for my independent ceiling. Im using figure 10.9 as my blueprint for getting drywall against the end joist.

By the way:
1) in Figure 4.20, is the 1x3 ledger board holding the drywall in place? Or is it only there for replacing the cross bridging?
2) Its described to screw the drywall/green glue sandwich directly to the underside of the subfloor.... I guess theres no worry about transmission through the screws? Its probably not a big deal. I just want to triple check! I only get to do this once
Old 2 weeks ago
  #9
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Kyle P. Gushue's Avatar
Quote:
Originally Posted by JMillz.Perc View Post
I see I see. Im using Figure 4.28 as well for my independent ceiling. Im using figure 10.9 as my blueprint for getting drywall against the end joist.

By the way:
1) in Figure 4.20, is the 1x3 ledger board holding the drywall in place? Or is it only there for replacing the cross bridging?
2) Its described to screw the drywall/green glue sandwich directly to the underside of the subfloor.... I guess theres no worry about transmission through the screws? Its probably not a big deal. I just want to triple check! I only get to do this once
1. You temp nail the new drywall in, toe nailing it to the stud (a powered finish nailer makes this easier). Then the ledger board holds the layers in, and you re-install the cross bridging. (Fig 4.21)

2. You can screw directly into the floor underneath, or toe nail like the diagrams. The added mass and existing floor are all a single unit acting as a whole, so no concern about the screws provided they dont penetrate up thru the floor. Either way you fasten them, you need the ledger board and bridging underneath, the screws/drywall can loosen over time from the deck flexing. I would tend to want to mud over the screw holes if i screwed them in. Ive not seen rod address wether or not mudding them is necessary.
Old 2 weeks ago
  #10
reinstalling the cross bridging will be a challenge for sure. Im nesting my independant ceiling rafters within the cavity between the existing joists. my 2x6 will hang down below the existing joist about 3", leaving me with an room ceiling of about 6'9".
Im looking in to the feasibility of using blocking between the existing joists instead of its original cross bridging, but installing it horizontally instead of vertically. Otherwise, the existing cross bridging, once replaced, would push my 2x6 down 3 more inches and give me a ceiling height of 6'6"
Old 2 weeks ago
  #11
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Kyle P. Gushue's Avatar
Quote:
Originally Posted by JMillz.Perc View Post
reinstalling the cross bridging will be a challenge for sure. Im nesting my independant ceiling rafters within the cavity between the existing joists. my 2x6 will hang down below the existing joist about 3", leaving me with an room ceiling of about 6'9".
Im looking in to the feasibility of using blocking between the existing joists instead of its original cross bridging, but installing it horizontally instead of vertically. Otherwise, the existing cross bridging, once replaced, would push my 2x6 down 3 more inches and give me a ceiling height of 6'6"
Figure 4.28 shows the bottom of the 2x6 ceiling 3&5/8" below the bottom of the floor joists, with the cross bridging.

Im unclear why you'd lose an additional 3 inches. Different floor joist spacing than the drawing??
Old 2 weeks ago
  #12
My existing joists are 16โ€ oc, but they are only 2x8. The issue with my build has always been that the distance from the bottom of my existing joists to the concrete floor is only 6โ€™11โ€ To begin with.
So losing 3&5/8โ€ by installing my new joist below the original cross bridging (fig. 4.28), and adding the additional 1&1/4โ€ for two sheets of 5/8 drywall brings my ceiling height down to 6โ€™6โ€ from the concrete.
Iโ€™m fighting for height.
My plan is to remove the original cross bridging and nest my new joists 2&1/2โ€ below the subfloor, which leaves room for two 5/8s GB and a 1&1/4 air gap to the top of my new joist.
My new 2x6 joist, then, will hang 1/2โ€ lower than the existing 2x8, leaving a 1/2โ€ air gap between the original joist and the drywall ceiling.
This allows me to have a ceiling height of about 6โ€™9โ€; a 3โ€ difference over Rods design.
But it eliminates me being able to use cross bracing

Checking my states code (pic attached), it seems to only require blocking if the joist exceeds a nominal 2x12.... am I interpreting that wrong? Because it seems like Iโ€™m not required to have it....

I am planning on running 1x3 horizontally between my existing joists every 4โ€™, just below the GB under the subfloor to have โ€œsomethingโ€...
My ceiling is only 19โ€™x11โ€™, roughly; my joists run the 11โ€™ span. So Iโ€™m not sure whether I really need the cross bridging...

Dissect, please! This is the only structural design issue I have.
Old 2 weeks ago
  #13
Oops! Hereโ€™s the section of code about bridging
Attached Thumbnails
Basement Sill Plate soundproofing options-69423dbb-e42e-46b2-9727-044501e7a080.jpg  
Old 2 weeks ago
  #14
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Kyle P. Gushue's Avatar
Quote:
Originally Posted by JMillz.Perc View Post
My existing joists are 16โ€ oc, but they are only 2x8. The issue with my build has always been that the distance from the bottom of my existing joists to the concrete floor is only 6โ€™11โ€ To begin with.
So losing 3&5/8โ€ by installing my new joist below the original cross bridging (fig. 4.28), and adding the additional 1&1/4โ€ for two sheets of 5/8 drywall brings my ceiling height down to 6โ€™6โ€ from the concrete.
Iโ€™m fighting for height.
My plan is to remove the original cross bridging and nest my new joists 2&1/2โ€ below the subfloor, which leaves room for two 5/8s GB and a 1&1/4 air gap to the top of my new joist.
My new 2x6 joist, then, will hang 1/2โ€ lower than the existing 2x8, leaving a 1/2โ€ air gap between the original joist and the drywall ceiling.
This allows me to have a ceiling height of about 6โ€™9โ€; a 3โ€ difference over Rods design.
But it eliminates me being able to use cross bracing

Checking my states code (pic attached), it seems to only require blocking if the joist exceeds a nominal 2x12.... am I interpreting that wrong? Because it seems like Iโ€™m not required to have it....

I am planning on running 1x3 horizontally between my existing joists every 4โ€™, just below the GB under the subfloor to have โ€œsomethingโ€...
My ceiling is only 19โ€™x11โ€™, roughly; my joists run the 11โ€™ span. So Iโ€™m not sure whether I really need the cross bridging...

Dissect, please! This is the only structural design issue I have.
Im interpreting the code the same as you, but i would just call the building dept to be sure. Im not a licensed builder, engineer, or architect. If it does require bracing maybe there are some unobtrusive ways to do it.

Two concerns of mine. The 1/2" airgap is like bare minimum afaik. Wood isn't perfect and can flex under load. It makes me concerned your cutting it too close. An inch is standard. Maybe shoot 3/4 if an inch is not doable.

The other one is if the resulting height on your current plan violates code for minum height? I think 6'8 is the min here in Massachusetts. Also are you counting the drywall mounted to the bottom of the new ceiling?
Old 2 weeks ago
  #15
Quote:
Originally Posted by Kyle P. Gushue View Post
Im interpreting the code the same as you, but i would just call the building dept to be sure. Im not a licensed builder, engineer, or architect. If it does require bracing maybe there are some unobtrusive ways to do it.
Ill put a call in today. I'm gonna pitch my idea of using horizontal 1x3s every 4' as an alternative to cross bridging.

Quote:
Originally Posted by Kyle P. Gushue View Post
Two concerns of mine. The 1/2" airgap is like bare minimum afaik. Wood isn't perfect and can flex under load. It makes me concerned your cutting it too close. An inch is standard. Maybe shoot 3/4 if an inch is not doable.
Thats a really good idea. I'll drop the ceiling another 1/2" to get a bigger gap. Thanks for the idea!

Quote:
Originally Posted by Kyle P. Gushue View Post
The other one is if the resulting height on your current plan violates code for minum height? I think 6'8 is the min here in Massachusetts. Also are you counting the drywall mounted to the bottom of the new ceiling?
I am taking the width of the two sheets of drywall in to consideration. I'm not 100% on how much Green Glue will add to the width, if anything, so in my calculations Ive been allowing for an 1/8 to 3/8" margin of error just in case.

My code says in order for a basement room to be considered a "living space", and therefor counted towards the total square footage of the home, the ceiling has to be 7ft. Anything less will not meet the requirements for a living space. Minimum height for any room, storage or otherwise, is 6'8".
Im shooting for 6'9".
Old 2 weeks ago
  #16
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Kyle P. Gushue's Avatar
Quote:
Originally Posted by JMillz.Perc View Post
Ill put a call in today. I'm gonna pitch my idea of using horizontal 1x3s every 4' as an alternative to cross bridging.



Thats a really good idea. I'll drop the ceiling another 1/2" to get a bigger gap. Thanks for the idea!



I am taking the width of the two sheets of drywall in to consideration. I'm not 100% on how much Green Glue will add to the width, if anything, so in my calculations Ive been allowing for an 1/8 to 3/8" margin of error just in case.

My code says in order for a basement room to be considered a "living space", and therefor counted towards the total square footage of the home, the ceiling has to be 7ft. Anything less will not meet the requirements for a living space. Minimum height for any room, storage or otherwise, is 6'8".
Im shooting for 6'9".
Good stuff.
Old 2 weeks ago
  #17
Talking

Quote:
Originally Posted by Kyle P. Gushue View Post
You want to seal between the foundation and the sill plate, it is not airtight and it needs to be. Even a 1/32" of an inch 12ft long, is a significant hole if you turn it into sqft. Use the sealing method described in the book
Hey Kyle! Check out the first pic. Itโ€™s a good view of a door to my garage....FROM MY BASEMENT foundation wall below the sill plate....so....

Found the culprit!!! (First attached picture). Almost changed my studios name to โ€œFlanking Pathway Productionsโ€.
Dealt with it!!! (Second attached picture) as per Rod Gervais
Sealed It!!! (Third pic) as per fire code.

Donโ€™t worry I did all my concrete walls as per โ€œthe bookโ€
Attached Thumbnails
Basement Sill Plate soundproofing options-d34fe9b0-0fec-40a5-9eea-0c51e8c223e9.jpg   Basement Sill Plate soundproofing options-25571b65-3254-4da7-b7c4-f2c3e0a10926.jpg   Basement Sill Plate soundproofing options-f390ac0f-ba52-4f5a-9d98-d1b8f88212c5.jpg  
Old 2 weeks ago
  #18
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Kyle P. Gushue's Avatar
Excellent work! Its great to see things done well. Maybe by the end of the build you will change the studio name to "Money Pit Productions" lol.

Cheers man.
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