Roof Deck Constructions, TGKX

Guide Information for Roofing Materials and Systems


Roof deck constructions illustrated and described in this category are identified by a construction number and evaluated as to the spread of fire on the underside and/or resistance to uplift forces.


Fire Classified Constructions are evaluated by either the large-scale fire test, or other test procedures having fire exposure conditions related to the large-scale fire test, described in the Standard for Fire Test of Roof Deck Constructions, ANSI/UL 1256.

These Fire-Classifications are not related to Fire ratings under either the Surface Burning Characteristics or the Fire Resistance Classification. The Surface Burning Characteristics is a comparative evaluation of materials (occasionally with facings or backing) with respect to flame spread and smoke developed. The Fire Resistance Classification is the time rating of an assembly with respect to resistance to flame passage, heat transfer and maintenance of structural integrity.

Roof deck constructions which are Fire-Classified consist of assemblies of materials as illustrated and described in this category, classified on the basis of specific requirements for maximum flame spread on the underside of the assembly within definite time limits. These constructions differ from materials classified with respect to Surface Burning Characteristics in that in the latter, materials are assigned comparative numerical values. They also differ from assemblies classified with respect to Fire Resistance, since temperature transmission through roof deck constructions and structural performance under load are not measured nor are time ratings assigned.

A fire investigation of a roof deck construction primarily determines whether the contribution to an igniting fire by any or all of the materials in the assembly is at a sufficient rate to cause propagation of flame on the underside, in excess of the established limits.

As indicated in individual Classifications, specific materials have been supplementally fire tested in accordance with the requirements of the indicated National Codes and Standards.

Authorities having jurisdiction are to be consulted as to which type of roof deck construction is acceptable for specific locations before installation.


Roof Deck Constructions Classified for Uplift Resistance have been investigated for damageability from both external and internal pressures on the deck associated with high velocity winds. Uplift Classifications are derived from tests conducted in accordance with the Standard for "Tests For Uplift Resistance of Roof Assemblies" , ANSI/UL 580. The ANSI/UL 580 test method subjects a 10 ft by 10 ft test sample to various static and oscillating air pressures to index performance under uplift loads imposed on roof decks.

The magnitude of the wind velocity across a roof deck and the resulting uplift pressures on a roof deck are dependent upon many factors such as wind gusts, the shape of the roof deck, edge configuration and the landscape surrounding the roof deck installation. A method to calculate the uplift pressures on roof decks is contained in the American Society of Civil Engineers (ASCE) Standard 7-95, Minimum Design Loads for Buildings and Other Structures.

The nominal static uplift pressure, the oscillating uplift pressures and the maximum static uplift pressure for each Class are:

Nom Static
Uplift Pressure
Range of
Oscillating Pressure
Max Static
Uplift Pressure
15 15 11 to 21 23
30 30 22 to 42 45
60 60 44 to 83 75
90 90 66 to 90 105

The static pressures are maintained for a 5 min period and the oscillating pressures are applied at a 10 plus or minus 2 s frequency and are maintained for a 60 min period for each Class. An assembly rated Class 60 has successfully withstood pressures imposed during Class 30 and Class 60 tests. An assembly rated Class 90 has successfully withstood pressures imposed during Class 30, Class 60 and Class 90 tests.

The test method provides a comparative measure of uplift resistance of roof deck constructions. The test evaluates the roof deck or roof deck assembly and its attachment to supports as well as the attachment of the roof covering, if used. For uplift resistance related exclusively to the securement of the roof covering to a specified type of roof deck see Classifications under Roofing Systems, Uplift Resistance (TGIK). Supporting structural members are evaluated only with respect to spacing and physical properties such as gauge, yield strength, grade and species of lumber and related factors, which could affect fastener attachment and necessary resistance to uplift forces. Secondary supports (beams, purlins, joists, bulb tees, lateral bracing, etc.), connections of the assembly to the main structural members (girders, columns, etc.) and construction details along the edges of the roof and around openings in the roof (skylights, chimneys, etc.) have not been evaluated unless specified in the construction. Constructions including skylights have been evaluated with single width skylight panels flanked on each side by a metal panel. Constructions including eaves/soffit have been evaluated for resistance to uplift pressures on the underside only.

Roof deck constructions consist of two groups. Construction illustrations and descriptions, beginning with Construction No. 1 include assemblies using metallic decks and constructions beginning with NM501 include assemblies using nonmetallic decks.

The specifications for the materials and their assembly are important details in limiting the flame spread on the underside of roof deck constructions or in resisting damage from high velocity winds. UL's Classification and Follow-Up Service is available for those materials so designated in the constructions described. The classifications of these materials are shown under Roof Deck Construction Materials (TGYV).

Metal Deck Assemblies

The metal deck assemblies illustrated are identified by a Construction Number.

Certain foam plastic insulation board products are acceptable for use in lieu of compressible fiberglass insulation in all roof deck constructions Classified for Wind uplift resistance in which the Metal Roof Deck Panels (TJPV) are directly fastened to structural members by means of self-drilling or self-tapping screws, or similar products. Refer to the Foamed Plastic (TJBX) category for information pertaining to the installation requirements.

Nonmetallic Deck Assemblies

The nonmetallic deck assemblies illustrated are identified by a construction number.

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Last Updated on 1998-12-26
TGKX.GuideInfo TGKX ACTIVE 19981226 19981226

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