I'd like to bring pex lines into my garage for a utility sink and washer. They will pass through a fire wall with type x drywall.

How should I properly penetrate this wall for pex? Should I get an intumescent collar for each individual pipe in its own penetration? Should I make a larger hole with a single collar and share it?

I'm in a single family residence when attached garage; living space above and beside the garage.

  • 1
    Are you in a single-family house with attached garage, or some sort of multi-family building? Jul 8, 2018 at 21:03
  • @ThreePhaseEel I added detail to the question. SFR attached garage.
    – Matthew
    Jul 9, 2018 at 0:09

1 Answer 1


First, this is a fire separation, not a true firewall

California Residential Code R302.6 (and the IRC it is based on) is clear on this point (italics in original):

R302.6 Dwelling/garage and/or carport fire separation The garage and/or carport shall be separated as required by Table R302.6. Openings in garage walls shall comply with Section R302.5. Attachment of gypsum board shall comply with Table R702.3.5. The wall separation provisions of Table R302.6 shall not apply to garage walls that are perpendicular to the adjacent dwelling unit wall. A separation is not required between the dwelling unit and a carport, provided that the carport is entirely open on two or more sides and there are not enclosed areas above.

So, you don't need to go crazy on this

From there, we chase down the reference to R302.5.3 on "other penetrations":

R302.5.3 Other Penetrations Penetrations through the separation required in Section R302.6 shall be protected as required by Section R302.11, Item 4.

Item 4 of R302.11, in turn, states:

Fireblocking shall be provided in wood-framed construction in the following locations:


  1. At openings around vents, pipes, ducts, cables, and wires at ceiling and floor level, with an approved material to resist the free passage of flame and products of combustion. The material filling this annular space shall not be required to meet the ASTM E136 requirements.

As a result of this, you don't need intumescent firestopping collars around these pipes at all, just something there (usually rockwool and a fire-resistive caulking) that will keep smoke and flames from slipping by around the pipe openings.

Since you're using intumescent collars, though, I'd use one collar/penetration per pipe -- since they work by expanding and pinching off the pipe, one-per-pipe is the only way to install them so that they'll work properly.

  • If collars are not required, can I just fill gap with rockwool? I'm trying to contextualize your last sentences.
    – Matthew
    Jul 9, 2018 at 5:07

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