Fire-Resistance rated Assemblies for Townhouse

[mccaldu]

Greetings,

We are using 2012 IRC however in our Municipality we have not adopted R313.1 (Townhouse fire sprinkler). Up to our adoption of 2012 the fire separation assemblies (2006) were 2- 1 hour walls and 2 - 1 hour assemblies through the roof trusses including non-combustable materials 4' on each side. Or a two hour common wall exception with limited penetrations. The 2012 exception in R302.2 allows for a common 1 hour wall with restricted penetrations. Our interpretation is that this 1 hour common wall exception works in conjunction with a firesprinkler system and when sprinklers are absent we require the 2 - 1 hour assemblies. My issue with a 1 hour common wall is that you could virtually have an infinite number of townhouses built in our jurisdiction without sprinklers, separated with only a 1 hour fire rated assembly. I have not found any discussions on where the 1 hour common wall exception came from. Does anybody know for sure if this exception came about from the change in firesprinkler requirements in the 2012 IRC?

Thanks in advance for any input.

D McCallum

 

[mjesse]

Your interpretation is correct.

The reduction to 1 hr. is written due to the requirement of sprinklers.

Remove the sprinkler requirement, you also need to up the separation factor.

...and welcome to The Forum!

mj

 

[Francis Vineyard]

Agree with that interpretation as Virginia deleted the sprinkler mandate and amended this section as follows;

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 ASTME 119 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. 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 through 43. Penetrations of electrical outlet

boxes shall be in accordance with Section R302.4. Notwithstanding

the above, if a townhouse development is fully

sprinklered as provided for in Section R313.1, a common

1-hour fire-resistance-rated wall shall be permitted between

townhouses.

 

[fatboy]

Agree with mjesse, and I was at the hearings when it passed, the down rating of the walls was based on the sprinklers. Get rid of the sprinklers, better be requiring 2-HR walls.

 

[fatboy]

And yes,

Welcome mccaldu!

 

[cda]

Welcome. MC

MC,

One hour = fire sprinklers

Two hour without sprinklers

 

[Fort]

In my opinion it would be better to require fire sprinklers in townhomes and allow the 1 hr common wall. Fire sprinklers save more lives than going to a 2 hr wall would ever be able to. The NFPA 13D systems are not that expensive, why not just adopt it as IRC has written it?

 

[fatboy]

There are others that would argue passive fire resistance is always better.

And, you don't even have to get to a 13D, you can use a combination system complying with P2904. We are seeing them for the lightweight framing protection going in at $75-100 a head. 3-4 heads.

 

[mccaldu]

Thanks

Thanks to all of the responses and I agree. In addition this is a great resource.

Greetings,We are using 2012 IRC however in our Municipality we have not adopted R313.1 (Townhouse fire sprinkler). Up to our adoption of 2012 the fire separation assemblies (2006) were 2- 1 hour walls and 2 - 1 hour assemblies through the roof trusses including non-combustable materials 4' on each side. Or a two hour common wall exception with limited penetrations. The 2012 exception in R302.2 allows for a common 1 hour wall with restricted penetrations. Our interpretation is that this 1 hour common wall exception works in conjunction with a firesprinkler system and when sprinklers are absent we require the 2 - 1 hour assemblies. My issue with a 1 hour common wall is that you could virtually have an infinite number of townhouses built in our jurisdiction without sprinklers, separated with only a 1 hour fire rated assembly. I have not found any discussions on where the 1 hour common wall exception came from. Does anybody know for sure if this exception came about from the change in firesprinkler requirements in the 2012 IRC?

Thanks in advance for any input.

D McCallum

 

[Fort]

And, you don't even have to get to a 13D, you can use a combination system complying with P2904....

You are talking about the same thing, 13D can be a very simple combination system. NFPA13D manual may be viewed online for free once registered here: http://www.nfpa.org/codes-and-standards/free-access