I-joists

Currently, there is no requirement for fire endurance of I-joists in single-family homes. There has been some fire testing done on floor and ceiling I-joist systems intended for multi-family residential and commercial structures where there are code-mandated standards.

The standard test protocol is an ASTM E119 burn. A test floor/ceiling, which is designed to carry a standard rated load and consists of an I-joist treated with gypsum, is set on fire. To pass, the bottom flange of the joist must stay intact for a target time.

An adhesive rating, certification and labeling system for fire-rated I-joists is currently in development by the Wood I-joist Manufacturers Association (WIJMA).

Glulam beams

Structural glue-laminated beams fall into the building code category of heavy timber and, therefore, are viewed as having excellent natural fire resistance. In the presence of fire, the outer portion of a glulam beam becomes charred. This layer of charred wood then acts as an insulator, helping to protect the undamaged interior of the beam from the heat. The ability of a glulam beam (minimum size of 6´ x 6´ or more before exposure) to resist fire for up to one hour is accepted in the 1997 Uniform Building Code (UBC). The American Institute of Timber Construction (AITC) has been revising its standards to stress the elevated temperature resistance criteria for adhesives used in glulam construction. Its specifications are found in the AITC 405-2005 standard and is referenced by AITC 200-2004.

Finger-jointed studs

In 2006, the American Forest & Paper Association (AF&PA) initiated a research program to better understand the importance of adhesives used in end-jointed lumber in fire-rated assemblies. As part of the research, the wood products industry – including Hexion – conducted fire-resistance tests on finger-jointed wall assemblies using many different adhesives. Based on findings from these tests, in February 2007 the AF&PA issued qualification criteria for finger-jointed lumber adhesives along with appropriate requirements for proper labeling for identification by building officials.

The new glued lumber policy provides for two testing methods. In both cases, an ASTM E119 procedure is prescribed, and the test wall assembly must pass a 60-minute burn. However, there are significant differences in the two tests with potential major ramifications for manufacturers.

Method A was designed to minimize the variables in test wall assemblies to ensure that adhesive systems are isolated for qualification. Adhesives that pass the Method A test can be adopted by any manufacturer with any wood species or grade and any finger joint geometry, and their end-jointed lumber manufactured with the adhesive may be stamped “heat resistant adhesive” (or “HRA”) without any further fire testing.

Method B was offered as an alternative for testing a finger-jointed stud system – that is, the wood species, grade, joint geometry, and adhesive system in total. Adhesives that pass Method B are only certified HRA with the specific lumber species, grade and finger joint geometry used in the test. Unless your manufacturing operation matches the test wall configuration exactly, additional testing will be required for HRA certification.

Fire-rated doors

For engineered wood doors made with adhesives to qualify for fire ratings, they must pass industry-standard burn tests, certified by industry sanctioning bodies. Tests include a series of exposures (depending on the rating) in a furnace followed by a hose stream test. The two industry sanctioning bodies are Underwriters Laboratory (UL) and Intertek.