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Fire-Retardant Treated Wood in Exterior Insulation and Finish Systems

Exterior Insulation and Finish Systems (EIFS) are widely used for non-bearing exterior walls, usually with gypsum board backing.

EIFS is proven and attractive, but it does have one shortcoming: in high wind areas, wind-borne debris can penetrate the wall. As a result, jurisdictions in these areas require EIFS backing that can resist the impact of a wind-borne missile.

The EIFS used in this project utilizes 5/8-inch Pyro-Guard plywood backing as a key component.

In addition to its fire-retardant capabilities, Pyro-Guard plywood is resistant to penetration from wind-borne debris and it provides high shear strength.

It is an economical and user-friendly alternative to corrugated steel, which is also used for impact-resistant EIFS backing in non-combustible buildings.

Insurance Recognition
Fire-retardant treated wood (FRTW) is recognized by the insurance industry as slow burning and is rated the same as steel or other noncombustibles. Also, the use of FRTW can earn significantly lower insurance rates compared to rates for untreated wood.

Code Section
South Florida Building Code, Section 2004: Exterior non-bearing walls with a 30-foot separation can be of FRTW in ordinary masonry construction.

SBCCI Standard Building Code, Table 600, Note k: Exterior non-bearing walls with 30-foot separation can be of FRTW in all types of construction.

ICBO Uniform Building Code, Section 503.4.3: Exterior bearing and non-bearing walls with a fire-resistance rating of two hours or less can be FRTW in ordinary masonry and heavy timber construction.

BOCA National Building Code, Section 1406:
Combustible materials can be used on the exterior side of exterior walls.