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Fire wall to protect exterior stair parallel and close to property line

Yikes said:
See https://up.codes/viewer/california/irc-2018/chapter/3/building-planning#R302.1

If I am reading it correctly, if all portions of your stair are at least 5' away from the adjacent property line, you will not have a fire rating requirement for this open stair.
Click to expand...
Thanks a lot. I was also thinking about R302.1. but I am a little confused, so the "exterior exit stairway" and the rule for being 10' away from PL does not apply here? What is my stairway categorized as?

Also, if I move it closer, i.e., 3' to PL, then I assume for fire rating I would need to put walls around it (which one of these options?)

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The original post #1 from 2011 was referencing 2010 CBC/ IBC 1027.3 .
1705098104736.png
That old 2010 CBC Section 1027 "Exit Discharge" is now called section 1028 in the 2022 CBC, and it no longer has similar 10' exit discharge requirement.
Instead, 2022 CBC 1027.5 is what requires exterior stairs to be 10' from the property line. But wait, notice exception #3:

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So what is an R-3 occupancy?
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That sounds like your project right?

But wait, again, we can arrive at the same conclusion more quickly than that, using the California Residential Code instead of the California Building Code. Look at chapter 1 of the 2022 CBC, "Scope and Administration", section 1.1.7.3.1 - - the choice is yours:
1705098028342.png

Since your building only has two dwellings, you can choose to ignore the CBC, and just focus on the CRC (as referenced in previous posts), which is probably easier to navigate and understand.
either way, it sounds like your 5' setback will be OK form a life-safety standpoint. (You'll also have to check local zoning codes, state ADU law, etc. that are under jurisdiction of the local planning department.)

All these life safety codes can be found here:
https://up.codes/codes/california
 
Thanks a lot for your time putting this valuable information together.

My original zoning was R1. Except from the fact that I can go with CRC, I am just curious about the fact that the exception for CBC code applies to R-3, perhaps my occupancy code will change to R-3 based on the added ADU? Please correct me if I am wrong.

Considering the CRC, I will probably try putting the stairway 3' away from PL (based on the allowed encroachments for my zone) and somehow make it fire-resistant based on the following table (maybe adding walls around it will be needed). Any thought or advice would be appreciated.

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