Code compliance of connecting two units of a duplex using a fire rated door

[brokenMotor]

I am a homeowner of a duplex in Sunnyvale California planning to do some renovation to this old house after tenants have moved out.

One of the things that come to my mind is connecting the two units using a fire rated interior door. That way it is more convenient to share living space with extended family members.

To visualize the change I am attaching the whole house floor plan which has the proposed location to add door marked.

I could not find a definite answer online saying whether this is allowed and I would like to seek your opinion.

Following is my own research:

2022 California Residential Code or 2021 International Residential Code has the following provisions:

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...

R302.4 Dwelling Unit Rated Penetrations
Penetrations of wall or floor-ceiling assemblies required to be fire-resistance rated in accordance with Section R302.2 or R302.3 shall be protected in accordance with this section.

R302.4.1.1 Fire-Resistance-Rated Assembly
Penetrations shall be installed as tested in the approved fire-resistance-rated assembly.

My understanding is that creating an interior door connecting both units is allowed as long as that interior door is 1-hour fire rated or better. Am I correct?

 

[Yankee Chronicler]

A door is not a penetration; it's an opening. The IRC doesn't contemplate openings (doors) in the rated wall between two dwelling units. You have to look in the IBC to find opening protectives in rated walls, and when you look there you'll find that the door should be a 1-hour (60-minute) rated door.

Is the door actually going to go where your plan shows it? That would mean that the rated wall takes a jog to enclose that closet. Like the IBC, the IRC requires that rated walls be supported by construction of the same fire-resistance rating all the way to the foundation. This means the entire floor of the lower unit in the plan has to be 1-hour rated. Assuming the straight wall (with the existing closet door in it) is the rated wall, it would make mores sense (MHO) to replace the closet door with a 1-hour fire door.

 

[BN4537]

We would not allow this to be done due to our zoning ordinances. No openings between duplexes, fire rated or not.

That's just a local thing here, but you might check to see if you have anything similar in your area. If you don't, the route YC is on is the correct way to approach it.

 

[redeyedfly]

A door is not a penetration; it's an opening. The IRC doesn't contemplate openings (doors) in the rated wall between two dwelling units. You have to look in the IBC to find opening protectives in rated walls, and when you look there you'll find that the door should be a 1-hour (60-minute) rated door.

Is the door actually going to go where your plan shows it? That would mean that the rated wall takes a jog to enclose that closet. Like the IBC, the IRC requires that rated walls be supported by construction of the same fire-resistance rating all the way to the foundation. This means the entire floor of the lower unit in the plan has to be 1-hour rated. Assuming the straight wall (with the existing closet door in it) is the rated wall, it would make mores sense (MHO) to replace the closet door with a 1-hour fire door.

Separation of units is a fire partition. Fire partitions only require 45min FRR doors. Supporting construction for unit separation is not required to be equal or greater than the rating of the fire partition (this exception is not in the residential code).



Table 716.1(2)

 

[brokenMotor]

OK I got a reply from the city plan checker and the proposal would not be allowed.

Unfortunately, creating a door between dwelling units would not be allowed. CRC 302.3 requires a one-hour fire separation between dwellings. This fire separation needs to be continuous from the foundation, all the way to the underside of the roof sheathing to prevent the spread of fire and smoke between dwelling units. The section related to penetrations (302.4) is for water pipes, gas pipes and other materials of this nature.

I think the only way you would be able to have this approved is if you first went to the Planning division and had the property converted to a single-family residence. I’m not sure what the process is for that or how long it would take. You would have to check with Planning. Still, even if you achieved this, you would have to remove one of the kitchens.

I’m afraid this just might not be feasible.

The interesting thing is that this house was built in 1956 and I have checked both the attic and the crawlspace and I do not see any sign of the "ideal" fire separation so the existing structure is not up to today's code.

Sample photo taken from the crawlspace near the topmost exterior wall. If the "ideal" fire separation exists it would make about half the crawlspace inaccessible and a separate crawlspace entrance is needed.



I guess there is no easy way forward.

 

[steveray]

OK I got a reply from the city plan checker and the proposal would not be allowed.



The interesting thing is that this house was built in 1956 and I have checked both the attic and the crawlspace and I do not see any sign of the "ideal" fire separation so the existing structure is not up to today's code.

Sample photo taken from the crawlspace near the topmost exterior wall. If the "ideal" fire separation exists it would make about half the crawlspace inaccessible and a separate crawlspace entrance is needed.

View attachment 14670

I guess there is no easy way forward.

The City is dumb.....and likely wrong....

 

[Yankee Chronicler]

I agree with steveray. A fire door does not violate the fire-resistance integrity of the fire barrier. Fire doors are called "opening protectives" in the IBC for a reason. In commercial work, we are allowed to put doors in 3-hour firewalls. There's no logical reason not to allow a 1-hour fire door in a 1-hour fire barrier.

 

[mtlogcabin]

The plans examiner is not the final say.

Does CA have something similar to this

R104.11 Alternative materials, design and methods of construction and equipment.
The provisions of this code are not intended to prevent the installation of any material or to prohibit any design or method of construction not specifically prescribed by this code. The building official shall have the authority to approve an alternative material, design or method of construction upon application of the owner or the owner’s authorized agent. The building official shall first find that the proposed design is satisfactory and complies with the intent of the provisions of this code, and that the material, method or work offered is, for the purpose intended, not less than the equivalent of that prescribed in this code in quality, strength, effectiveness, fire resistance, durability and safety. Compliance with the specific performance-based provisions of the International Codes shall be an alternative to the specific requirements of this code. Where the alternative material, design or method of construction is not approved, the building official shall respond in writing, stating the reasons why the alternative was not approved.

 

[Joe.B]

The plans examiner is not the final say.

Does CA have something similar to this

R104.11 Alternative materials, design and methods of construction and equipment.

Yes, that's in our code.

Also, ask the plan reviewer for a code reference citing that a single-family residence can't have two kitchens? They won't be able to find one. I've heard the argument (from planners) that if it "walks like a duck..." but that's total B.S. What if I want a kitchen area in my garage so when I cook my crab I don't stink up the whole house? Or I want an outdoor sink next to my grilling station? What about a wet-bar in my den? Doesn't exist.

 

[mtlogcabin]

You still have a duplex even if there is an adjoining door connection similar to adjoining rooms in a hotel.
Change your floor plan and create an entry vestibule shared by both units. Now you can secure the building at the vestibule entry door and each duplex unit have their individual entry doors that can be left wide open when sharing the living space with shared family members

 

[steveray]

Change your floor plan and create an entry vestibule shared by both units.

Careful you will work your way right out of the IRC....

R101.2​

The provisions of this code shall apply to the construction, alteration, movement, enlargement, replacement, repair, equipment, use and occupancy, location, removal and demolition of detached one- and two-family dwellings and townhouses not more than three stories above grade plane in height with a separate means of egress

 

[mtlogcabin]

Careful you will work your way right out of the IRC....

Good point the kitchen doors would have to be designated as the means of egress doors out of each unit for the vestibule idea to comply with the IRC.