Building additions while preserving egress for existing

[andyaz]

Hi all, I'm a contractor in the Phoenix area, and am trying to think of a way to build an addition (attached ADU) for a customer while preserving the egress requirements for their bedrooms. Typically when I build an ADU like this, it's detached or at a part of the home where I can add egress windows to another wall.

With this home's layout, the only place for the addition is on the side of the house has a bunch of bedrooms, and the only exterior wall (hence egress) for two of them is that wall. I'm chewing on ways to get this done, and came up with this. The(alley? courtyard? patio cover?) would chew into the space but I think preserve egress requirements.

As for the roof, this is a typical ranch home and I'll just extend the roof line out; the east wall in this picture will be a gable wall.

I think as long as the distance between the exterior walls is 36", we're good to go as far as egress, but I'm having trouble finding the particular section of the IRC for this.

Initially, we talked about a detached structure but the lot is too tight and the setbacks eat into it too much

Would love to hear your thoughts and/or better ideas

(dimensions here were arbitrary, except the alley- figuring 3')

 

[Yankee Chronicler]

Is this located in Phoenix and subject to the Phoenix Residential Code, or is it outside of Phoenix where only the Arizona Fire Code applies?

 

[andyaz]

Is this located in Phoenix and subject to the Phoenix Residential Code, or is it outside of Phoenix where only the Arizona Fire Code applies?

Good Q, this particular one is in Mesa. They use 2018 IFC and from what I see not many amendments relating to residential structures (https://www.mesaaz.gov/Public-Safety/Mesa-Fire-Medical/Fire-Prevention/Fire-Code/Fire-Code-Details)

I'm guessing 1hr fire assembly on the new ADU walls will be required at a minimum as well

if I need to retrofit the existing walls... oof, putting up type x on the inside wouldn't be that big of a deal but the existing house is t1-11 sided. pain to retrofit, maybe typeX or densglass + stucco on top.