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Townhouse separation wall continuity

Glenn

Registered User
Joined
Nov 1, 2012
Messages
889
Location
Denver
I think the subject of townhouse wall continuity has reached a point of Frankenstein that it's time to consider a total revision of the sections. (not the applications, just the presentations) Let me explain.

R302.2.2 common walls: Has provisions for the common wall to extend to the underside of sheathing and exterior walls. A new exception was added in 2021. But isn't that why we have the next section.

R302.2.3 Continuity: These provisions are for both common and double wall, but refers to "the fire-resistance-rated wall..". It basically repeats much of what is the section above, but adds a few more details about attached accessory structures.

R302.2.4 Parapets for townhouses: Now we learn that the above two sections only work when you use the exception from this section. Here we learn the general rule is the "common wall or exterior wall" (does that mean "double wall") actually can't stop at the underside of the sheathing, and really has to extend through the roof. Oh but wait... there is an exception that does allow you to terminate it under the sheathing.

I feel like these three sections have gotten clunky and disconnected over the years of modifications. I think there are two many different terms used for the same features. This is on my 2027 IRC proposal wish list to clean up without changing the application. I think the ability to easily read and consistently interpret the code is as important as anything it actually says. I welcome your thoughts and collaboration.
 
As someone once said ICC does not stand for Intelligent Clear & Concise. So, thanks for taking the lead on this section in trying to accomplish that
 
I'm curious what you think about "common wall" in Exceptions 2 and 4.

 
Maybe look at it this way??

302.2.2 refers to a common wall as a specific entity with specific properties and restrictions, and maybe would be better titled "single wall".
303.2.6 refers to a generic entity and would apply to either "double walls" or "single walls", and maybe as you say, be better titled "separation wall".

But I think this section has always been a mess.
 
Maybe look at it this way??

302.2.2 refers to a common wall as a specific entity with specific properties and restrictions, and maybe would be better titled "single wall".
303.2.6 refers to a generic entity and would apply to either "double walls" or "single walls", and maybe as you say, be better titled "separation wall".

But I think this section has always been a mess.
That's exactly how I look at it. But since it quite clearly uses the words "common wall" in those exceptions I want to get more consensus that "The words are wrong" Thank you for sharing your thoughts.
 
  • Double wall was added to the IRC
  • Double wall was not added to the exception
  • Either it was left out of the exception intentionally OR
  • The code panel completely dropped the ball
 
  • Double wall was added to the IRC
  • Double wall was not added to the exception
  • Either it was left out of the exception intentionally OR
  • The code panel completely dropped the ball
Double wall was not added to the IRC. Double wall is just the original Townhouse where two exterior walls were placed at zero FSD.

Dear Lord, for Christmas please give Jeff the courage to realize that the I-Codes are created by us, not some "code panel" and to bravely share his own professional opinions in threads under the category: "code development discussions"
 
Here is what I see:
1671728759108.png

This is what is new in the IRC that suddenly added Double Walls which was never in the code before. How is this not a change?
1671728883175.png
 
Before double wall appeared in 2018, the method was simply exterior walls of single family dwellings with zero FSD. That would have two walls (i.e. "double wall"). The IRC always referenced townhouses back to the exterior wall section, but gave an exception for the common wall method. The code language you see today dates back to the 1986 CABO code. That is when the townhouse common wall method appeared with parapets and structural independence. The language for roof flashing in the 2021 IRC, exception 4 is identical to when it first appeared in the CABO code in 1986 (read that again). From 1986 CABO to 2000 IRC, there was more evolution of the provisions. Townhouses were considered the dwelling unit and were considered "separate buildings". Today they are considered one building. We have also seen introduction and the increase of use of shaft wall systems as a common wall. The original "common wall" method was a conventional wall.

I well research subjects before I teach them. When I find the words don't make sense, I write code proposals. Before that I seek input from others. The monster I am addressing here was born in 1986, and has been patched and pieced together since then. Jeff, I feel like I'm spending my time convincing you there is a problem that needs to be addressed, not discussing how to address it. If you think it's perfect as is, then I appreciate that feedback. Thank you and I have no further argument in that respect.
 
Like Glenn said....CT has been tweaking it a bit for 10 years or so and ICC is just catching up....This was our 2016 amendment...

(Amd) R302.2 Townhouses. Each townhouse shall be considered a separate building and shall be separated by fire-resistance-rated wall assemblies meeting the requirements of Section R302.1 for exterior walls.
Exception: A common 2-hour fire-resistance-rated wall assembly tested in accordance with ASTM E119 or UL 263 is permitted for townhouses if such walls do not contain plumbing or mechanical equipment, ducts or vents in the cavity of the common wall. If the adjacent townhouses are provided with an automatic residential fire sprinkler system, this wall may be a 1-hour fire-resistance-rated wall assembly. The wall shall be rated for fire exposure from both sides and shall extend to and be tight against exterior walls and the underside of the roof sheathing. Electrical installations shall be installed in accordance with Chapters 34 to 43, inclusive. Penetrations of electrical outlet boxes shall be in accordance with Section R302.4.
 
Virginia (2018) has a similar amendment:

R302.2.2 Common walls.

Common walls separating townhouses shall be assigned a fire-resistance rating in accordance with Item 1 or 2. The common wall shared by two townhouses shall be constructed without plumbing or mechanical equipment, ducts or vents, other than water-filled fire sprinkler piping, in the cavity of the common wall. The wall shall be rated for fire exposure from both sides and shall extend to and be tight against exterior walls and the underside of the roof sheathing. Electrical installations shall be in accordance with Chapters 34 through 43. Penetrations of the membrane of common walls for electrical outlet boxes shall be in accordance with Section R302.4.

1.Where a fire sprinkler system in accordance with Section P2904 is provided, the common wall shall be not less than a 1-hour fire-resistance-rated wall assembly tested in accordance with ASTM E119, UL 263 or Section 703.3 of the International Building Code.

2.Where a fire sprinkler system in accordance with Section P2904 is not provided, the common wall shall be not less than a 2-hour fire-resistance-rated wall assembly in accordance with ASTM E119, UL 263 or Section 703.3 of the International Building Code.
 
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