Industry Voices: Learn Not to Burn
When specifying fire resistive materials, selection of the appropriate UL fire resistance design is of paramount importance. Most UL designs are specific to a manufacturer, construction assembly, hourly rating and material type. In order to narrow down what is needed for your project, you need to have an understanding of the directory.
This specific volume within the series of UL Fire Resistance Directories contains fire-rating classifications based upon ANSI/ UL 263 (ASTM E119 and NFPA 251) and ANSI/UL 1709.
Subdivided for your Convenience
Although it may look overwhelming to a first time user, the UL Fire Resistance Directory is well structured and relatively simple to use. It utilizes an alphanumeric system in order to designate the type of assembly being protected and the type of material used to protect the construction assembly. Each letter designates a specific type of assembly. These types are separated into categories along with their corresponding letter designations; floor and ceiling-D and G Series; concrete slab-J Series; floor beams and joists-N Series; roof and ceiling-P Series; roof beams and joists-S Series; columns-X, Y & XR Series; and walls and partitions-U Series.
The various types of passive fire protection products are categorized along with their corresponding number designations: rigid board fire resistive materials-300 Series; gypsum board-500 Series; SFRMs-700 and 800 Series; and intumescent coatings-600 Series. Unprotected assemblies (not requiring fire protection to the underside of decking) which utilize these various types of fire protection products for the structural steel members are classified in the 900 Series designs.
It is also important to note that beams and joists are included in two types of test assemblies. One type of assembly contains a full representation of the floor or roof construction. These systems will determine a protection method on both the deck (if necessary) and the supporting beams and joists. These are identified in the D, G, J and P Series letter designations. The other type of assembly is a partial representation of the floor or roof construction. These systems only determine thicknesses on the supporting beams and joists and are commonly used for beam substitutions. These allow for thicknesses advantages, hourly ratings or beam types that are not available within the assemblies and are identified in the N and S Series letter designations.
Mix and Match
Beam substitutions are permitted in accordance with the introductory portion of the UL Fire Resistance Directory, Volume 1. In order to substitute an N or S Series beam into a D, G, J or P Series assembly, it must contain the same UL classified fire resistive material and must be used within assemblies that have similar or greater heat dissipation if the floor or roof construction specified within the design in which the beam is being transferred.
For example, you can substitute an N Series floor beam and joist into a D, G or J Series floor and ceiling assembly. However, you cannot substitute an N Series floor beam into a P Series roof and ceiling assembly.
Determining the hourly fire resistance ratings and the construction assemblies requiring the hourly ratings is essential. Hourly ratings are determined based on model building code criteria.
Hourly ratings are expressed in both restrained and unrestrained classifications. The restraint classification must be made by the project structural engineer and is one of the most important criteria in selecting the appropriate UL design.
It should be understood that the intent of the International Building Code is that the building is considered unrestrained unless otherwise indicated on the drawings by the structural engineer.
It is also important to note that the introductory portion of the UL Fire Resistance Directory, Volume 1 has specific criteria that need to be met in order for the construction type to be considered restrained. The required thickness of fire protection material may vary depending upon the construction assembly’s classification.
The items needed in order to determine the appropriate UL design for floor and ceiling assemblies, at minimum, are the type(s) of fire protection product to be used, hourly rating requirement, depth of the floor decking, minimum thickness and type of concrete (lightweight or normal weight) and minimum structural steel size.
To select the appropriate UL design for roof and ceiling assemblies, you need to determine, at minimum, the type(s) of fire protection product to be used, hourly rating requirement, depth of the roof decking, type(s) of insulation used and the minimum structural steel size.
Measure Twice, Cut Once
The UL Fire Resistance Directory, Volume 1 allows for various thickness calculations for both beams and columns. Beam thicknesses are determined based on the tested member listed in the design for the specified hourly rating and utilizing the beam thickness adjustment formula as listed in the introductory portion of the UL Fire Resistance Directory for alternate beam sizes. Column designs list both tested member minimum types and sizes and typically list alternate formulas to determine thicknesses.
Beams and wide flange columns are expressed in terms of W/D ratio. Hollow, shaped tube steel members are expressed in terms of A/P ratio.
Once you have the basic understanding of the UL Fire Resistance Directory, you should be able to determine the appropriate design needed.
Most manufacturers of UL classified fire resistive materials provide technical support in assisting you with the design selection process and thickness required.