# Retrofit ceiling/ floor for ADU



## J2architect (Sep 28, 2020)

We have a 2 story type V building with 2 apartment units on the 2nd floor and we are converting an existing storage space on the 1st floor into an ADU. how do you retrofit the floor between units to comply with the 1 hour fire rating and 50 stc requirement without having to tear out the finish floor on the upper units? Is there a UL or certified testing number we can use to respond to the plan check comment?


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## ICE (Sep 28, 2020)

Well then  I learned something new today.  I didn't know that an apartment building is fair game for an ADU.  Are you within the city of Whittier or the unincorporated part of Whittier?

GA FILE NO.  FC 5120


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## mark handler (Sep 28, 2020)

FIND A TESTED ASSEMBLY THAT IS CONSISTENT WITH THE FRAMING AND HAVE THE ALTER THE CONSTRUCTION TO MATCH




AN ARCHITECT SHOULD KNOW THIS STUFF....


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## mark handler (Sep 28, 2020)

ICE said:


> Well then  I learned something new today.  I didn't know that an apartment building is fair game for an ADU.  Are you within the city of Whittier or the unincorporated part of Whittier?


AS OF JANUARY 2020


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## cda (Sep 28, 2020)

J2architect said:


> We have a 2 story type V building with 2 apartment units on the 2nd floor and we are converting an existing storage space on the 1st floor into an ADU. how do you retrofit the floor between units to comply with the 1 hour fire rating and 50 stc requirement without having to tear out the finish floor on the upper units? Is there a UL or certified testing number we can use to respond to the plan check comment?



Welcome !!!!

Took you long enough to formulate a question


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## cda (Sep 28, 2020)

Build 


J2architect said:


> We have a 2 story type V building with 2 apartment units on the 2nd floor and we are converting an existing storage space on the 1st floor into an ADU. how do you retrofit the floor between units to comply with the 1 hour fire rating and 50 stc requirement without having to tear out the finish floor on the upper units? Is there a UL or certified testing number we can use to respond to the plan check comment?




Build a one hour ceiling on 1st floor

If you can reference IBC, try a calculated approach


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## J2architect (Sep 28, 2020)

ICE said:


> Well then  I learned something new today.  I didn't know that an apartment building is fair game for an ADU.  Are you within the city of Whittier or the unincorporated part of Whittier?
> 
> GA FILE NO.  FC 5120



I am within the city but this applies throughout California. Thank you for the GA file, but this applies to new construction, do you know if there is another method for existing floor/ ceiling to be retrofitted from the underside?


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## ICE (Sep 28, 2020)

mark handler said:


> AS OF JANUARY 2020


Pretty soon every car wash will have an ADU.


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## cda (Sep 28, 2020)

J2architect said:


> I am within the city but this applies throughout California. Thank you for the GA file, but this applies to new construction, do you know if there is another method for existing floor/ ceiling to be retrofitted from the underside?



Besides the sound you only need one hour rating??

Densglass shaftliner or similar or once again IBC and calculate it


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## cda (Sep 28, 2020)

Read thru this and see if any help







						Existing Home Garage Conversion to ADU
					

Not required but can't they be used in lieu of 1 hr? what is need for 1-hour? Unit seperation? IMPO, NO



					www.thebuildingcodeforum.com


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## J2architect (Sep 28, 2020)

cda said:


> Read thru this and see if any help
> 
> 
> 
> ...



Thank you for the suggestion. I am running into the same issue as he did. Trying to find an existing assembly that meets the stc 50 requirement.


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## cda (Sep 28, 2020)

Sorry I know nothing about stc 50, but if you make your own sandwich of some type using this

TABLE 721.2.1.4(2)
TIME ASSIGNED TO FINISH MATERIALS ON FIRE-EXPOSED SIDE OF WALL

And sound material to get stc 50???????????


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## cda (Sep 28, 2020)

some light reading




			https://nationalgypsum.com/ng/File/THESOUNDBOOK.pdf


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## north star (Sep 29, 2020)

*$ ~ $ ~ $*

Can you use Rockwool, Safe'n'Sound Insulation to increase the STC ?
See the Link:
*


			https://www.rockwool.com/products/safensound/?selectedCat=safensound%C2%AE%20downloads#Specifications&Sizes
		

*
*< = < = < = <*


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## Paul Sweet (Sep 29, 2020)

Gypsum Association GA-610-02 discusses membrane protection for existing unrated assemblies.  It might no longer be available.

Gypsum Association GA-600-2018 _Fire Resistance and Sound Control Design Manual_ has the most current listing of rated assemblies.  The 2012 edition can be viewed on-line: 


			GA-600-12-web-version-1.pdf


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## Robert (Oct 7, 2020)

J2architect said:


> Thank you for the suggestion. I am running into the same issue as he did. Trying to find an existing assembly that meets the stc 50 requirement.


You can always field test the assembly after construction rather than rely on an existing tested assembly for sound. The advantage is they give you an extra 5db allowable, The disadvantage is, if it doesn't pass you are left with fixing it to comply.


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## MACV (Oct 9, 2020)

Try Kinetics IsoMax or equal "resilient sound isolation clips" and hat channels (RSIC-1). UL Design No. L583 (two layers 5/8" type X drywall for 1 hr.)


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## ADAguy (Oct 16, 2020)

Careful with reducing interior ceiling height when doing this.


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