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Advertising supplement provided by
National Gypsum Company

The computer will display assembly details, including a cross-section and a narrative of assembly methods and procedures. You can then cut and paste assembly details directly into specifications. Most of the gypsum-related assemblies can be found in construction groups 500-599. It should be noted that the UL directory is not copyrighted, and that, in fact, the UL encourages direct transfer of its assembly specifications to your bid and building plans.

The UL’s Fire Resistance Directory Vol. 1, available online, provides a guide to the designs within. The first 10 pages of Vol. 1 give specifiers an explanation of terms and standards that apply to the UL assembly designs.

“I am always surprised, in my teaching, to find how few professionals have read this,” Piccolo says. “These 10 pages tell you how to use the book. The answers to many of the most frequently asked questions about drywall systems are found here.”

A few key items from the first 10 pages that we should be aware of are as follows:

• Page 2, column 2: “Nails and Screws.” “Screws meeting ASTM C1002 or ASTM C954 may be substituted for nails, one for one, when the head diameter, length, and spacing equal or exceed the requirements for the specified nails.” So can screws be substituted for nails? Yes! Provided the fasteners meet the above requirements.
• Page 3, column 1: “Gypsum Board Orientation.” Vertically applied gypsum board is applied with the long edges parallel to the framing members to which it is attached. Horizontally applied gypsum board is gypsum board applied with the long edges perpendicular to the framing members to which it is attached. The orientation is critical to ensure that assemblies are fire-resistant.
• Page 3, column 1: “Gypsum Board Joint Treatment,” (Fire Taping).
  The key point under this heading is “Base layers in multi-layer systems are not required to have joints or fastener heads taped or covered with joint compound.”
• Page 4, column 2: “Steel Joists.” This section explains that the joist sizes in a design are minimums. “Joists which exceed the specified minimum size may be used provided the accessories are compatible.”
• Page 5, column 1: “Gypsum Board” The main point of this section is that gypsum board thicknesses specified are minimums. “Greater thickness of gypsum board is permitted as long as the fastener length is increased to provide penetration into framing that is equal or greater than that achieved with the specified gypsum board thickness and fasteners.”
  Note: Additional layers of gypsum board can be added to any design.
• Page 8, column 1: “Blanket Insulation.” We learn in this section that in a ceiling and floor or roof system the addition of insulation, if not specified in the design, may reduce the hourly rating of the assembly. So, in assemblies of the G500, L500 and P500 series, you may add insulation provided an additional layer of gypsum wallboard is added to the assembly. In wall assemblies, insulation is optional unless otherwise stated.
• Page 9, column 2: “Wall and Partition Assemblies.” “The size of studs are minimum unless otherwise stated in the design. The spacing of studs are maximum unless otherwise stated in the design.”
• Page 10, column 1: “Metal Thickness.” Metal thicknesses are minimums unless the design indicates a specific gauge. If metal thickness is not specified in the design, reference the table on page 10 of UL Vol. 1 for gauge and metal thicknesses.

“I can’t tell you how many jobs I’ve been on where they didn’t follow this guide and put the drywall on the wrong way. It, then, has to come down upon inspection,” Piccolo says. “You can take this information directly from the website, so that when the contractor bids the job, and when he builds it, he has no reason not to put it up the right way.”

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