Can someone point me were to find a stc rating of 50 for existing wood floor assembly consisting of 3/4" t&g plywood and 2x10's. the floor needs to have a 1 hour separation so im adding sound batts and (2) layers 5/8 typ 'X' g.w.b. (essentially RC 2601) The building inspector is telling me this assembly is unacceptable unless I can prove the stc is 50
Thanks
Chad Miller
Jul 1, 21 1:19 pm
Ask a local architect in your area and pay them for their time.
s=r*(theta)
Jul 1, 21 3:13 pm
I honestly dont mind paying, but pay to just have a 10 min conversation of "blah blah blah?
Missed the part where it needs to also have a '1 hour separation'. I assume this means a 1 hour fire rating. No idea if it's a fire wall or partition.
s=r*(theta)
Jul 1, 21 3:04 pm
its a floor/ceiling
JLC-1
Jul 1, 21 3:38 pm
the existing wood floor is a problem if it doesn't have sound board underneath, a sound test would show anything done in the ceiling below as insufficient - the channel and the glue helps a lot, but it's the impact sound that's difficult.
Everyday Architect
Jul 1, 21 1:42 pm
When I'm in this type of position I usually call up a helpful gypsum board rep. They usually have something close that has been tested for both hourly rating and STC. If not, you might need to get into resilient channels on the bottom of the 2x10s or something that has been tested for STC.
Chad Miller
Jul 1, 21 2:02 pm
You can also use the UL Design Wizard.
Everyday Architect
Jul 1, 21 2:17 pm
Good luck with that. When I just looked at it I started by identifying floor-ceiling assemblies. Then limited those to wood joist assemblies. Then entered in the hourly rating. Then clicked on the STC rating and "no results found."
Really the UL search only shows one floor-ceiling assembly with an STC rating (STC 60 is the only option available to select) ... and it's using steel joists with concrete floor. https://iq.ulprospector.com/en...
YMMV
Chad Miller
Jul 1, 21 2:34 pm
Are you using the Product iq that requires a login or the general search?
Chad Miller
Jul 1, 21 2:42 pm
Didn't see the link. Yup - the OP is screwed. Going to have to use an existing assembly with engineered beams and argue that the the dim lumber has performs better.
Looks like the OP will need to ::gasp:: actually hire an architect to do some calculations and argue their case to the building department!
Everyday Architect
Jul 1, 21 2:52 pm
Chad, the OP is a regular here and an architect. They posted the following back in Feb 2019 "Im a licensed PM w/ 14yrs of experience at a small 6 person office w/ 85% of our projects being multifamily and strip malls."
Chad Miller
Jul 1, 21 2:56 pm
Then they should probably know how to figure this out . . . .
All joking aside. This is going to be a tough assembly to create. The OP may need to work with the building department to see about using separate assemblies.
Yes I am licensed in multiple states and I have never run into this condition. the original building is a 6 plex built in 1964, 4 units up, 2 units down. at some point they gutted a lower unit and used it as a assembly space / multi-purpose / meeting room. flash fwd to June 2021 the owner wants to convert it back to a dwelling unit given no one is gathering as often because of covid, as I explained the exist. floor / ceiling in OP, clearly the existing assembly is not even 1hr rated nor has the min stc of 50, my next move is to argue the existing building code and where we are not reducing the standard but equal or greater that the existing
Jay1122
Jul 2, 21 11:12 am
Ah, so it is a bottom unit with units above still occupied. You can only work on the bottom of the floor. RC channel is definitely not enough. I would go with the spring isolator. Anyway, use the existing code, see if you can get away.
Jay1122
Jul 2, 21 11:22 am
Ah found it. This will satisfy.
Well, this is fun searching for these things. I care about acoustic performance deeply even in a single family house. Going to need it when I design my own house one day.
we do existing timber and wood a ton and always use resilient on ceilings... others have already commented as much, but I'm a bit surprised with the "oh, a toughy, hmm, might have to use RC channel" is RC channel really considered that much of a $ add to people?
SneakyPete
Jul 1, 21 4:35 pm
Why does a building inspector give a fuck about STC?
JLC-1
Jul 1, 21 4:49 pm
I'm actually glad he does, I would love to have the time and money to test my apartment, I'm pretty sure it doesn't meet code. (I dont have a newer IBC on pdf)
Chad Miller
Jul 1, 21 4:49 pm
Same reason why a building inspector would care about fire ratings. It's required by local building code.
Everyday Architect
Jul 1, 21 4:49 pm
Maybe because it's a code requirement.
SneakyPete
Jul 1, 21 5:47 pm
That'll teach me to stay away from multi-family. :P
Chad Miller
Jul 1, 21 6:44 pm
Yeah, I'm doing a small milti-family project now. Only need 1/2 rated fire partition with an STC of 50 for floors and walls that separate units. Compared to what the OP is dealing with it's easy.
s=r*(theta)
Jul 1, 21 10:49 pm
Chad, im used to new construction or demo and remodel, I think this is the first in my career where im fitting up or a converting a 700s.f. assembly space back into a dwelling unit in a small milt-family how it was originally designed.
Chad Miller
Jul 2, 21 11:19 am
Are you in the US? I ask because if you're in Canada then the GA assemblies can work. If you're in the US the it's only UL assemblies or a prescriptive assembly.
Jay1122
Jul 1, 21 5:45 pm
This is probably what I would go with. NO UL listed but it is a standard assembly listed by the manufacturer with testing info meeting the criteria. Just add self leveling to the t&g wood and you only need one layer of gyp.
Chad Miller
Jul 1, 21 6:41 pm
I was thinking the OP would have to use some type of prescriptive, non UL assembly like that.
s=r*(theta)
Jul 1, 21 11:09 pm
the problem with the prescriptive is that stc is typically done by assembly, and not by material
SneakyPete
Jul 2, 21 12:38 am
What about hiring an acoustic consultant to write up a report? Give it a little heft?
atelier nobody
Jul 2, 21 2:15 am
GA-600
Chad Miller
Jul 2, 21 11:18 am
Again - dose the OP need a UL assembly? If so the GA's will not work.
Chad Miller
Jul 2, 21 12:04 pm
s=r - that's a good point. Also with a prescriptive assembly you have to convince the AHJ to accept what you're proposing.
b3tadine[sutures]
Jul 2, 21 12:35 pm
I was able to convince the AHJs that my calculated method worked, and it saved the client a couple hundred grand.
Chad Miller
Jul 2, 21 12:50 pm
It can work. All depends on the architect and the AHJ. Sometimes the AHJ will only accept listed assemblies. I've had both success and failures using the prescriptive method.
Can someone point me were to find a stc rating of 50 for existing wood floor assembly consisting of 3/4" t&g plywood and 2x10's. the floor needs to have a 1 hour separation so im adding sound batts and (2) layers 5/8 typ 'X' g.w.b. (essentially RC 2601) The building inspector is telling me this assembly is unacceptable unless I can prove the stc is 50
Thanks
Ask a local architect in your area and pay them for their time.
I honestly dont mind paying, but pay to just have a 10 min conversation of "blah blah blah?
Isn't that what we do though?
https://www.soundproofingcompa...
Missed the part where it needs to also have a '1 hour separation'. I assume this means a 1 hour fire rating. No idea if it's a fire wall or partition.
its a floor/ceiling
the existing wood floor is a problem if it doesn't have sound board underneath, a sound test would show anything done in the ceiling below as insufficient - the channel and the glue helps a lot, but it's the impact sound that's difficult.
When I'm in this type of position I usually call up a helpful gypsum board rep. They usually have something close that has been tested for both hourly rating and STC. If not, you might need to get into resilient channels on the bottom of the 2x10s or something that has been tested for STC.
You can also use the UL Design Wizard.
Good luck with that. When I just looked at it I started by identifying floor-ceiling assemblies. Then limited those to wood joist assemblies. Then entered in the hourly rating. Then clicked on the STC rating and "no results found."
Really the UL search only shows one floor-ceiling assembly with an STC rating (STC 60 is the only option available to select) ... and it's using steel joists with concrete floor. https://iq.ulprospector.com/en...
YMMV
Are you using the Product iq that requires a login or the general search?
Didn't see the link. Yup - the OP is screwed. Going to have to use an existing assembly with engineered beams and argue that the the dim lumber has performs better.
Looks like the OP will need to ::gasp:: actually hire an architect to do some calculations and argue their case to the building department!
Chad, the OP is a regular here and an architect. They posted the following back in Feb 2019 "Im a licensed PM w/ 14yrs of experience at a small 6 person office w/ 85% of our projects being multifamily and strip malls."
Then they should probably know how to figure this out . . . .
All joking aside. This is going to be a tough assembly to create. The OP may need to work with the building department to see about using separate assemblies.
depending on the floor finish and if they can add anything to it, they aren't that far off it seems ... https://www.certainteed.com/resources/techinfo/GypsumCAD_BIM/pdf/GA-FILE-NO-FC-5120.pdf
Dose it have a UL listing?
Yes I am licensed in multiple states and I have never run into this condition. the original building is a 6 plex built in 1964, 4 units up, 2 units down. at some point they gutted a lower unit and used it as a assembly space / multi-purpose / meeting room. flash fwd to June 2021 the owner wants to convert it back to a dwelling unit given no one is gathering as often because of covid, as I explained the exist. floor / ceiling in OP, clearly the existing assembly is not even 1hr rated nor has the min stc of 50, my next move is to argue the existing building code and where we are not reducing the standard but equal or greater that the existing
Ah, so it is a bottom unit with units above still occupied. You can only work on the bottom of the floor. RC channel is definitely not enough. I would go with the spring isolator. Anyway, use the existing code, see if you can get away.
Ah found it. This will satisfy.
Well, this is fun searching for these things. I care about acoustic performance deeply even in a single family house. Going to need it when I design my own house one day.
These Genie Clips are another option: https://pliteq.com/products/sound-control-clip/genieclip-rst/. Not sure about fire ratings. Call the rep to verify.
Check the gyp board manufacturers. STC 50 might be trouble - looks like you might be in resilient channel territory.
https://www.usg.com/content/us...
https://buildgp.com/assemblies...
https://www.nationalgypsum.com...
GA-600
Does the OP need a UL listing though?
That can be found in GA-600.
we do existing timber and wood a ton and always use resilient on ceilings... others have already commented as much, but I'm a bit surprised with the "oh, a toughy, hmm, might have to use RC channel" is RC channel really considered that much of a $ add to people?
Why does a building inspector give a fuck about STC?
I'm actually glad he does, I would love to have the time and money to test my apartment, I'm pretty sure it doesn't meet code. (I dont have a newer IBC on pdf)
Same reason why a building inspector would care about fire ratings. It's required by local building code.
Maybe because it's a code requirement.
That'll teach me to stay away from multi-family. :P
Yeah, I'm doing a small milti-family project now. Only need 1/2 rated fire partition with an STC of 50 for floors and walls that separate units. Compared to what the OP is dealing with it's easy.
Chad, im used to new construction or demo and remodel, I think this is the first in my career where im fitting up or a converting a 700s.f. assembly space back into a dwelling unit in a small milt-family how it was originally designed.
Are you in the US? I ask because if you're in Canada then the GA assemblies can work. If you're in the US the it's only UL assemblies or a prescriptive assembly.
This is probably what I would go with. NO UL listed but it is a standard assembly listed by the manufacturer with testing info meeting the criteria. Just add self leveling to the t&g wood and you only need one layer of gyp.
I was thinking the OP would have to use some type of prescriptive, non UL assembly like that.
the problem with the prescriptive is that stc is typically done by assembly, and not by material
What about hiring an acoustic consultant to write up a report? Give it a little heft?
GA-600
Again - dose the OP need a UL assembly? If so the GA's will not work.
s=r - that's a good point. Also with a prescriptive assembly you have to convince the AHJ to accept what you're proposing.
I was able to convince the AHJs that my calculated method worked, and it saved the client a couple hundred grand.
It can work. All depends on the architect and the AHJ. Sometimes the AHJ will only accept listed assemblies. I've had both success and failures using the prescriptive method.