[GSBN] Fwd: [nbne] SB fireblocking

Fri Mar 14 02:51:01 UTC 2014

Hello folks, 

This comes from our NBNE list.  Jim Luckner who sent it, asked me to forward to GSBN as well. He is working with an owner-builder on a house for which the code officer is interpreting a need for fireblocking within the straw bale wall to prevent fire from spreading through the wall cavity in a HORIZONTAL manner. (The code also addresses fire-blocking in vertical context, but that's not an issue in this particular design). The code section in question comes from NYSRC which he assumes comes straight from the IRC. The entire section is attached, but relevant parts:

R602.8 Fireblocking required. 

Fireblocking shall be provided to cut off all concealed draft openings (both vertical and horizontal) ... Fireblocking shall be provided in wood-frame construction in the following locations.   

1. In concealed spaces of stud walls and partitions, including furred spaces and parallel rows of studs or staggered studs; as follows:  

1.1. Vertically at the ceiling and floor levels. 

1.2. Horizontally at intervals not exceeding 10 feet (3048 mm).  AND

R602.8.1 Materials. 

...fire blocking shall consist of 2-inch (51 mm) nominal lumber, or [...other wood products, gypsum or cement board...].  Batts or blankets of mineral wool or glass fiber or other approved materials installed in such a manner as to be securely retained in place shall be permitted as an acceptable fire block. ... Loose-fill insulation material shall not be used as a fire block unless specifically tested in the form and manner intended for use to demonstrate its ability to remain in place and to retard the spread of fire and hot gases. 
To the latter part, it would seem:
1. the straw bales are being "securely retained in place" (he admits this was a little vague in the drawings, but probably staked, attached to timber frame posts, &/or wires interlocked). To my mind, any  bale wall stacked tight enough to provide a good plaster base and avoid significant air leakage - even if only primarily secured to each other - seems considerably more secure than fiberglass batts tacked occasionally to studs.
2. the straw bales, being baled are not "loose-fill" and even if they were,  straw bale fire test results have shown them to demonstrate their "ability to remain in place and to retard the spread of fire and hot gases."
Someone already sent him a copy of the 2006 ATSM 1 hour fire resistance test for non-bearing strawbale wall, but if anyone else has additional resources for him to use, or has successfully dealt with this issue before, he'd love to hear of it. 

Jim's on this list as read-only, so you can reply to the group and he'll see it, or reply to me & I can forward, or reply to him directly at the email below. 

Thanks all!

ej

ej George, CSBA

----- Forwarded message from jimluckn at hvi.net -----
    Date: Wed, 12 Mar 2014 23:17:04 -0400
    From: Jim Luckner <jimluckn at hvi.net>
Reply-To: nbne at lists.riseup.net, Jim Luckner <jimluckn at hvi.net>
Subject: [nbne] SB fireblocking
      To: nbne at lists.riseup.net

Hi:

   I'm involved with a strawbale project under construction in midlands of  code-crazy-New York, wherein the local building inspector is interpreting section 602.8 of the  Residential Code to require horizontal fireblocking  within strawbale walls  - that means breaking the running bond and shoving a in continuous floor to floor strip of sheetrock or such every 10 feet. I'm wondering if anyone else has had to deal with this and/or know of any precedents in this regard.

The building has 2 stories, with 2x6 inset studs + headers platform framed to support roof load.  We have one section of wall on the ground floor with inset interior 2x4 studs supporting the 2nd floor framing.  The rest of the 2nd floor is supported on interior columns.  The finishes will be plasters applied directly to the bale faces, with no furring and no "concealed spaces" in the walls.  Some air movement is obviously possible through the voids in the bales, though no more, i'd think, than through fiberglass or mineral wool batts, which can be considered fire blocking under the code.  The bales are unlikely to fall out of the wall unless there's a partial or general collapse of the wood framing.  And, of course, if bales are falling, they're not really falling out of the wall; the wall is falling and any talk of "concealed draft openings" will be rather silly.

-jim

Jim Luckner
(845)658-3635
jimluckn at hvi.net

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