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Status: Decision Rendered
Appeal ID: 11693 Project Address: 2025 NE 55th Ave
Hearing Date: 3/25/15 Appellant Name: Jack Barnes
Case No.: B-013 Appellant Phone: 503-232-1620
Appeal Type: Building Plans Examiner/Inspector: Joe Disciasio
Project Type: residential Stories: 3 Occupancy: R-3 Construction Type: V-N
Building/Business Name: Fire Sprinklers: No
Appeal Involves: Erection of a new structure LUR or Permit Application No.: 14-188365-RS
Plan Submitted Option: pdf   [File 1] Proposed use: R-3 Single-Family Home


Appeal item 1

Code Section

R302.11, R302.11.1


R302.11.1.2 Requirement: “Fireblocking shall be provided... in concealed spaces of stud walls and partitions. Horizontally at intervals not exceeding 10 feet.”

Code Modification or Alternate Requested
Proposed Design

Proposed wall will not include fireblocking behind stud wall since the typical airspace will be instead filled with rigid insulation, eliminating any concealed space. Dense-packed insulation will fill stud cavities.

Note that fireblocking will be maintained at wall/floor transition.

This assembly has been discussed with Sr. Inspector Joe Disciasio at the project site.

See attached details on sheet AP-1.

Proposed basement wall design from outside-to-inside:
• Concrete foundation wall.
• 1” thick R-Tech EPS foam with reflective barrier facing interior. Tape all joints. (Note that this product is also considered acceptable as an exposed material in crawl spaces, due to the foil-face reflective barrier.)
• 2x4 stud-framed cavity wall built tight to the EPS foam. Insulate cavities with Dense-Packed cellulose insulation (considered an acceptable fireblocking material per OSSC 718.2.1, item 8).
• 1/2” Gypsum wallboard as interior finish.
Note that the code section calls for fireblocking to “cut off all concealed draft openings”. By filling the airspace completely, we will eliminate any and all draft openings.

Reason for alternative

We are building a home that aims for low energy use and durability of materials/assemblies, with insulation values that will exceed code requirements. Preventing condensation and moisture transfer are key strategies for durability. Interrupting the R-Tech barrier (for fireblocks) will compromise the thermal performance and will introduce risk of moisture damage to the wood-framed wall.

Respected experts in building science recommend this wall assembly without any interruption of the foam layer. (See attached sheet AP-3 w/ detail excerpted from “BSC Information Sheet 511” published by Building Science Corporation & Joe Lstiburek.)

According to the IBC Commentary, ”the intent of fireblocking is to reduce the ability of fire, smoke and gases to move to different parts of the building through combustible concealed spaces.” The proposed assembly does not create any concealed spaces because the 1-inch space will be completely filled with R-Tech insulating panels. This is far different from attempting to use foam as a fireblock material.

Additionally, the use of Dense-Packed cellulose (NOT loose-fill) will completely fill the cavity, acting as a fire block to separate the stud cavities. (The use of cellulose insulation as a fireblocking material was officially recognized by the ICC and added to the 2012 IBC.) See attached sheet AP-4 w/ document titled : “Cellulose Fire Blocking and Ignition Barrier Capabilities”.

The proposed basement walls will be capped with traditional fireblocking to prevent vertical flame spread to the floor above and to any wall cavities above.

There may be some concern that the proposed EPS foam would combust, leaving an empty airspace behind the stud wall (in this scenario, source of ignition would be from electrical wall boxes within the stud cavity). This is not a real risk for the following reasons:

• R-Tech foam is tested to have a Flash Point Temperature of 610° F and an Autoignition Temperature of 850° F. See attached MSDS sheet on sheet AP-5. Residents will have ample opportunity to escape the home before temperatures reach these levels in any fire.
• R-Tech foam is treated with a Bromine Flame Retardant, and has a flame-spread index of 15 (class A).
• Electrical boxes (switches, outlets, etc.) in the wall cavity are to be protected with “Soudafoam Fireblock” foam at all holes & wiring penetrations, to prevent ignition of the wall assembly. See sheet AP-6 for ICC report for the Soudafoam product.
• Space behind Electrical boxes in the cavity will be filled with dense-packed cellulose (considered a fireblocking material, per OSSC 718.2.1, item #8). This provides superior fire separation as compared to a wall insulated with fiberglass batts, which typically leave large voids around electrical boxes.
• The house will not have any combustion appliances, and will not have natural gas service. (i.e. no risk of fire from gas furnace or gas water heater). Other common sources of basement fires include the clothes dryer, which will instead be located on the top floor of this home. Electric-resistance heaters will NOT be used, since the house is equipped with a ductless mini-split heat pump system.
• The placement of R-Tech against the basement wall, with wood framing against the foam sheathing, is within the parameters of the manufacturer’s recommended installation. See attached sheet AP-2 for the detail from Insulfoam.


Insulation of furred wall cavity in lieu of fireblocking: Granted as proposed.

The Administrative Appeal Board finds that the information submitted by the appellant demonstrates that the approved modifications or alternate methods are consistent with the intent of the code; do not lessen health, safety, accessibility, life, fire safety or structural requirements; and that special conditions unique to this project make strict application of those code sections impractical.