I-Joist Floor Assemblies

In the case of field-applied fire protective paints, the same requirements for field-applied fire coatings apply, including the ASTM E119 fire test demonstrating equivalence to 2x10 dimension lumber or structural composite lumber.

Mineral wool insulation is commonly available in most metropolitan areas. Contact material suppliers or distributors that handle the product for costs.

I-joist web holes should be cut prior to the installation of the ceramic blanket. Then the blanket can be cut at the web hole location with a utility knife. Either of these steps can be done before or after the I-joists are installed.

Yes, because a fire is unlikely to reach a joist from only one side.

No, the gypsum membrane covering I-joists is not required to be finished with tape and joint compound for equivalent performance to nominal 2 x 10 lumber floors. In the same way, joints between 5/8-inch wood structural panel membranes are not required to be taped and finished.

If the suspended ceiling system is fire-rated as equivalent to the fire performance of 1/2-inch gypsum on the underside of the I-joist framing, it is considered an alternative to the fire protection requirements in accordance with the first paragraph in the 2015 IRC Section R302.13 and 2012 IRC Section R501.3.

No, APA does not work with any manufacturers of field-applied coatings. However, individual I-joist manufacturers themselves may have such relationships. I-joists coated with an approved field-applied coating are required to demonstrate the same equivalency to 2 x 10 dimension lumber or structural composite lumber as the fire protective membrane methods published in APA System Report SR-405, in addition to several other requirements, such as the effects, if any, of the coating on the structural properties of the I-joists. APA suggests contacting both the coating manufacturer and the I-joist manufacturers that recommend such applications for product approvals.

This question has been addressed by the International Code Council (ICC) and some states. The ICC issued a written interpretation indicating that:

Exception 4 permits floor framing of sawn lumber or structural composite lumber equal to or greater than 2 x 10 nominal dimension to be exempted from the application of the protective membrane to the underside of the floor framing members. The basis for this exception is that tests conducted on floor framing constructed of 2 x 10 lumber and loaded to 50 percent of full design load showed that the assemblies provided adequate time for occupants’ self-evacuation and safety for firefighters performing search and rescue. Floor assemblies using wood trusses may be approved for exemption if the floor assembly demonstrates equivalent fire performance.

Therefore, in order to apply this exemption to floor trusses, the trusses must be tested and evaluated for equivalency to the fire performance of nominal 2 x 10 lumber. This interpretation is consistent with the ruling by several states, such as the Ohio Board of Building Standards (BBS) and Massachusetts Board of Building Regulations and Standards (BBRS). Those rulings are available from the states' respective web sites.

As reported by the American Wood Council (AWC), fire testing with an 80-square-foot unprotected area showed that, for a fire occurring under a protected area, fire blocking provides a minimal level of performance of the membrane system. The 80-square-foot allowance in the 2015 IRC Section R302.13 and 2012 IRC Section R501.3 is intended for passage of multiple HVAC or plumbing through floor penetrations, provided the aggregate area of the penetrations does not exceed 80 square feet per story and fire blocking is installed in accordance with Section R302.11.1 along the perimeter of the unprotected portion, separating the unprotected portion from the remainder of the floor assembly.

See Table R702.3.5 of the 2015 or 2012 IRC.

Based on an engineering analysis in accordance with the 2015 IRC Section 702.3.5, 1 x 4 (nominal) wood furring strips can be installed perpendicular to the bottom flange of I-joists at 16 inches on center, provided that the gypsum boards are directly attached to the furring strips using 1-1/4-inch (32 mm) Type W drywall screws at 12 inches (305 mm) on center. This provides the same number of fasteners with the same fastener penetration depth into the framing as gypsum directly attached to the I-joist flange, and is in compliance with the 2015 IRC Table R702.3.5.

Yes, but FP-02 requires only the I-joist web to be protected.

Refer to APA System Report SR-405 for specific requirements and exceptions.

Yes. In a March 2015 E-Memo released by the Massachusetts Department of Public Safety, the I-joist fire protective membrane methods published in APA System Report SR-405 are specifically recognized as compliant with the BBRS Official Interpretation (No. 2014_03) when used in conjunction with an APA Product Report or ICC-ES Evaluation Report to signify compliance with the Massachusetts code.

This comment gets to the intent of the IRC code requirement. These requirements are intended to increase the fire safety for occupants and firefighters in lightweight residential floors. Yes, the solutions add costs to varying degrees, but they also add benefits—the primary benefit being the increased fire performance of the floor assembly.

If basement ductwork interferes with the installation of gypsum to the underside of the I-joists, the ductwork can be framed-in so that the gypsum protection is provided around the HVAC chase, similar to what is typically done when basements are finished.

A factory-applied intumescent coating by itself does not qualify an I-joist or plated truss to meet the membrane protection requirement for Exemption No. 4 in section R302.13 of the IRC. The I-joist would still need to be qualified under ICC Acceptance Criteria 14 (AC14). This Acceptance Criteria specifies testing according to the ASTM E119 time temperature curve, loading of the joists, consideration of holes, and durability requirements for the Intumescent coating. Field-applied intumescent coatings are outside of the scope of AC14.

If fire retardant treated wood (FRTW) was used to manufacture a plated floor truss, the floor truss system would still need to be qualified to demonstrate equivalence to IRC Section R302.13, Exception 4. ICC-ES AC14 is specific to wood I-joists. APA is not aware of any similar ICC-ES Acceptance Criteria for metal plated floor trusses. Contact your plated truss manufacturer for information regarding the use FRT members in trusses.

“Portions of floor assemblies shall be permitted to be unprotected where complying with the following, 3.1 and 3.2,”

Exception 3.2 requires blocking be installed along the perimeter of the unprotected space in order to separate the unprotected portion from the remainder of the floor. Such blocking must be installed in accordance with Section R302.11.1, which lists several fire-blocking options, such as:

1. Two-inch (51 mm) nominal lumber
2. Two thicknesses of 1-inch (25.4 mm) nominal lumber with broken lap joints.
3. One thickness of 23/32-inch (18.3 mm) wood structural panels with joints backed by 23/32-inch (18.3 mm) wood structural panels.
4. One thickness of 3/4-inch (19.1 mm) particleboard with joints backed by 3/4-inch (19.1 mm) particleboard.
5. One-half-inch (12.7 mm) gypsum board.
6. One-quarter-inch (6.4 mm) cement-based millboard.
7. 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.
8. Cellulose insulation installed as tested in accordance with ASTM E 119 or UL 263, for the specific application.