2 hr block firewall, with rake up to the bottom of the fire rated plywood. Fire wool between the rake and the plywood. Don't you still have to have fire caulk for an air tight envelope ? I don't think fire wool alone is sufficiant to block air flow. ( duplex ).
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fire wool without fire caulk
- Thread starter mrose
- Start date
Yankee Chronicler
Registered User
Where is PSL? Are you in the U.S. or in Canada?
In the U.S., under the IBC any penetrations through a firewall have to be sealed with a listed penetration seal assembly. I can't recall ever seeing a listed assembly that didn't have fire caulk over the fire wool.
But you're not talking about a penetration, you're asking abiout the intersection of the firewall to the roof desk. Under the IBC that requires a listed joint seal assembly. Are the blocks solid, or hollow-core? Are they stepped, or are they cut to match the slope of the roof deck?
In the U.S., under the IBC any penetrations through a firewall have to be sealed with a listed penetration seal assembly. I can't recall ever seeing a listed assembly that didn't have fire caulk over the fire wool.
But you're not talking about a penetration, you're asking abiout the intersection of the firewall to the roof desk. Under the IBC that requires a listed joint seal assembly. Are the blocks solid, or hollow-core? Are they stepped, or are they cut to match the slope of the roof deck?
TheCommish
Registered User
install in accordance with the listed requirements of the system
steveray
SAWHORSE
This is a "hotly" debated topic....pun fully intended....I say you need a listed joint detail.....Code is struggling to quantify this and I am not sure why...
You say duplex, so not necessarily a FW or fire barrier, but from IBC fire barriers (i suspect that the IRC has even less guidance so whatever the BO says, goes):
And from the "joints" section...
You say duplex, so not necessarily a FW or fire barrier, but from IBC fire barriers (i suspect that the IRC has even less guidance so whatever the BO says, goes):
707.9Voids at intersections.
The voids created at the intersection of a fire barrier and a nonfire-resistance-rated roof assembly or a nonfire-resistance-rated exterior wall assembly shall be filled. An approved material or system shall be used to fill the void, and shall be securely installed in or on the intersection for its entire length so as not to dislodge, loosen or otherwise impair its ability to accommodate expected building movements and to retard the passage of fire and hot gases.And from the "joints" section...
ICE
Oh Well
707.8 Joints. Joints made in or between fire barriers, and joints made at the intersection of fire barriers with underside of a fire-resistance-rated floor or roof sheathing, slab or deck above, and the exterior vertical wall intersection shall comply with Section 715.
715.1 General. Joints installed in or between fire-resistance-rated walls, floor or floor/ceiling assemblies and roofs or roof/ceiling assemblies shall be protected by an approved fire-resistant joint system designed to resist the passage of fire for a time period not less than the required fire-resistance rating of the wall, floor or roof in or between which the system is installed. Fire-resistant joint systems shall be tested in accordance with Section 715.3.
715.2 Installation. A fire-resistant joint system shall be securely installed in accordance with the manufacturer’s installation instructions and the listing criteria in or on the joint for its entire length so as not to impair its ability to accommodate expected building movements and to resist the passage of fire and hot gases.
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steveray
SAWHORSE
Thanks ICE...busy morning and lost that step...
Take note that this was posted in the residential section. The code sections provided are from the IBC, and the IRC may be the applicable code.
If this is an IRC structure, the following code section applies. Also note that it is no longer a fire wall, but a fire-resistance rated wall.
2021 IRC 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 where tested in accordance with ASTM E119, UL 263 or Section 703.2.2 of the International Building Code. Such separation shall be provided regardless of whether a lot line exists between the two dwelling units or not. Fire-resistance-rated floor/ceiling and wall assemblies shall extend to and be tight against the exterior wall, and wall assemblies shall extend from the foundation to the underside of the roof sheathing.Exceptions:
- A fire-resistance rating of 1/2 hour shall be permitted in buildings equipped throughout with an automatic sprinkler system installed in accordance with Section P2904.
- Wall assemblies need not extend through attic spaces where the ceiling is protected by not less than 5/8-inch (15.9 mm) Type X gypsum board, an attic draft stop constructed as specified in Section R302.12.1 is provided above and along the wall assembly separating the dwellings and the structural framing supporting the ceiling is protected by not less than 1/2-inch (12.7 mm) gypsum board or equivalent.
If the block wall cannot be extended upward to be tight to the roof sheathing, then I would propose the use of the fire wool and an elastomeric firestop spray. This configuration would not directly follow the IRC, but would follow the IBC as a joint per the aforementioned IBC Section 707.8. To find an appropriate design, I would do a search for a listed top-of-wall joint via UL Product iQ or similar.
Inspector Gadget
Registered User
What does the system require?
That's the only question. Fire-stop systems MUST be ULC approved. If the assembly can't be subsumed under a listed (tested) system, the installer will have to tear things out and start from scratch.
Any firewall must also be a smoke barrier, fyi. So your instincts are correct, but the hammer lies in the fire-stop requirement.
Keep in mind, this is likely not a fire wall as it is residential construction (duplex per OP). It is only a fire-resistance rated wall. Under the IRC, head of wall joints are not required.
Inspector Gadget
Registered User
I read "firewall" which is a fire separation in my world. I recognize that some folks use "fire wall" where "fire separation" or "fire-rated assembly" was intended, but on a forum such as this, I assume - for good or ill - that folks are using terms correctly.
I agree... and would assume the same where the post is from someone who regularly talks code. That said, those who deal with code at an arms length often call any and all fire resistance-rated walls "firewalls." Given the context of the OP, I think it is safe to presume that the OP is not dealing with a proper firewall.