• Welcome to The Building Code Forum

    Your premier resource for building code knowledge.

    This forum remains free to the public thanks to the generous support of our Sawhorse Members and Corporate Sponsors. Their contributions help keep this community thriving and accessible.

    Want enhanced access to expert discussions and exclusive features? Learn more about the benefits here.

    Ready to upgrade? Log in and upgrade now.

Existing Home Garage Conversion to ADU

P

PC_Number

REGISTERED
Joined
Aug 16, 2019
Messages
6
Location
visalia, california
Problem:
Existing 2 story home would like to convert the existing 1st floor Garage to ADU. Code section R302.3 requires a 1-hr floor assembly between the two dwelling units, and 1-hr rating at the supporting construction. What have you seen as design solutions. People will not want to reconstructed the floor assembly to create the 1-Hr rated assembly.
One possible solution is shown in the link below:
https://www.portlandoregon.gov/bds/appeals/index.cfm?action=getfile&appeal_id=14189&file_id=14773

I am looking for a tested listed and approved retrofit 1-hr fire rated floor assembly or any creative solutions.
Any help or insight would be greatly appreciated.
 
I am a plans examiner. Just wondering what other jurisdictions have approved in the past. The problem is creating a 1-Hr fire separation at the ADU and Main Dwelling units between the 1st and 2nd floor without having to redo the second floor framing to create a listed 1-hr rated floor and ceiling assembly.
 
PC_Number said:
I am a plans examiner. Just wondering what other jurisdictions have approved in the past. The problem is creating a 1-Hr fire separation at the ADU and Main Dwelling units between the 1st and 2nd floor without having to redo the second floor framing to create a listed 1-hr rated floor and ceiling assembly.
Click to expand...


Not into design, but how about something like shaftliner?

https://cache1.buildgp.com/wp-conte...aftwell-stairwell-systems-technical-guide.pdf


Does your city have any written guidance on ADU,,

or just use base code?
 
Good Idea with the Shaft Liner I was thinking along the same lines but shaft liners are for "walls". I have looked into the gypsum association listed assemblies. Again, they have a lot of approved wall assemblies but not much for floor rated assemblies.
 
PC_Number said:
Good Idea with the Shaft Liner I was thinking along the same lines but shaft liners are for "walls". I have looked into the gypsum association listed assemblies. Again, they have a lot of approved wall assemblies but not much for floor rated assemblies.
Click to expand...


Not into all that design stuff,

But does the code just require one hour seperatation ??


Base code not calif

R302.3 Two-family dwellings.
Dwelling units in two-family dwellings shall be separated from each other by wall and floor assemblies having not less than a 1-hour fire-resistance rating where tested in accordance with ASTM E 119 or UL 263. Fire-resistance-rated floor/ceiling and wall assemblies shall extend to and be tight against the exterior wall, and wall assemblies shall extend from the foundation to the underside of the roof sheathing.
 
We have dimensional lumber.
CDA: Look at section R302.3.1 Supporting Construction.
This requires elements that support the 1-Hr Fire Rated Assembly to get the 1-hour rating too.
 
Support beam and post will need to be protected that supports the floor above. Do you have access to a gypsum catalog for a 1-hr protection design?
 
If the joist are 16" OC then you can use IBC chapter 7 other wise it is not hard to find one hour floor ceiling assemblies
Remember the fireside is the ceiling and 2 layers of type X or C is all most assemblies use
The fireside for supporting construction in the conversion of the garage is the interior side so again it will be a simple single or double layer to achieve this unless CA have amended the IRC
 
If it is Accessory no, if it is Additional, yes....At least around here....And the entire garage would have to meet current energy code including floor/slab...That is what usually gets them here, but you do not have as harsh of a climate...Can you use 721 IBC or whatever the archaic assemblies section is?
 
steveray said:
If it is Accessory no, if it is Additional, yes....At least around here....And the entire garage would have to meet current energy code including floor/slab...That is what usually gets them here, but you do not have as harsh of a climate...Can you use 721 IBC or whatever the archaic assemblies section is?
Click to expand...
Here too, but unless it is attached, or close to a Property line, no need for one-hour
 
You must log in or register to reply here.
Back
Top