HD27 - Premature Deterioration of Fire-Retardant Treated Plywood

  • Published: 1993
  • Author: Department of Housing and Community Development
  • Enabling Authority: House Joint Resolution 238 (Regular Session, 1992)

Executive Summary:
This study on the premature deterioration of fire-retardant treated plywood used as roof sheathing was conducted by the Department of Housing and Community Development in response to House Joint Resolution 238 of the 1992 General Assembly. The study requested the Department to develop a particular protocol to determine the structural characteristics and durability of the products and to give consideration as to whether a separate five-year warranty period should be enacted.


The Department determined in its study of the premature deterioration of fire-retardant treated plywood used as roof sheathing that failure of certain products is due largely to exposure to elevated temperatures which activates chemical reactions causing strength loss. In many cases the reaction is severe enough to require replacement of the material.

The Department also determined that the development of a protocol for determining structural characteristics and durability of FRT plywood is currently under way at the national level by a consortium of trade and industry groups. The American Society for Testing and Materials (ASTM) has approved an emergency protocol standard, ES 20-91, and is currently balloting a companion standard known as the Standard Practice for Establishing Allowable Spans and Loads for Fire Retardant Treated Plywood Roof Sheathing. In addition the American Wood Preservers Association is currently striving to develop a procedure for standardizing FR-treating formulations.


The Department believes that the Virginia Uniform Statewide Building Code (USBC) should be based on nationally recognized standards developed utilizing a consensus process which includes a wide representation from industry, code enforcement, engineering and technical fields. To reproduce the standard writing process currently used at the national level for use in developing state-wide standards would require extensive expenditures of both time and money and would seem to duplicate unnecessarily efforts already underway on a national basis.

The Department recognized that the USBC provisions relating to the approval of FRT plywood were in need of clarification to give the building official clear guidance in whether the products were to be approved. In addition, it was recognized that there are FRT plywood products on the market and in use which have not experienced failure, one of which has been in use for over ten years. The national model code organizations' National Evaluation Service Committee has currently issued approvals based on extensive evidence submitted for two specific products, neither of which have had any reported incidents of failure since their development.


To clarify the current requirements of the USBC relating to the approval of FRT plywood sheathing, the State Building Code Technical Review Board was requested to issue an official interpretation. Staff submitted to the Board all documentation which was received during the public comment period and subsequent public hearing held by the Department relative to this issue. The Review Board ruled that the Building official is not required to accept the use of FRT plywood sheathing since nationally recognized standards for determining its structural characteristics and durability are still in the process of being developed and have not been incorporated into the USBC. They further ruled that in determining whether to approve the use of a specific product, the building official may consider approvals issued by the nationally recognized model code organizations' evaluation services.


The Department does not recommend legislative action to ban of the use of FRT plywood, recognizing that with the issuance of the Technical Review Board interpretation, building officials are unlikely to approve its use without adequate documentation to assure its structural performance and durability. The Department and the Board of Housing and Community are currently preparing to update the USBC under the procedures of its public participation guidelines and the Administrative Process Act. During the public input phase of that process, the Board may determine whether to reference the new national standards for FRT plywood in the USBC if they are finalized at that time or, if substantiated by public comment, may delete the provisions of the code permitting the use of FRT plywood until such time as national standards are deemed to be adequate.

The Department believes that legislative action to extend the warranty period for FRT plywood roof sheathing used in new construction is appropriate and will serve to ensure adequate product performance until such time as national standards have been fully developed and incorporated into the Uniform Statewide Building Code. A recommendation for proposed legislation is included in Appendix A of this document.

It is further recommended by the Department that the General Assembly consider establishing a legislative commission to explore possible options for helping homeowners resolve existing problems with FRT roof installations.