FRTW: myths and market opportunities

By Glenn W. Wilson Manager-Technical Services Hoover Treated Wood Products. Inc.

F RTW (fire retardant treated

Jt woodt has a bright future due to test methods that assure good long term structural performance and increased usage in commercial, institutional and multi-family residential projects. With warranty coverage unprecedented in the building materials industry, acceptance by building officials is facilitated by new code compliance reports which include evaluation of high temperature strength testing for roof applications.

In spite of several decades of successful use, including World War II blimp hangars still standing and holding the world's record for the largest wood structures ever built, several myths and misunderstandings persist relative to FRTW.

MYTH 1: FRTW is corrosive and eats up fasteners.

Current fire retardant treatments are not corrosive although "first generation" treatments used prior to the early 1980s were relatively hygroscopic

(attracting water from moist air) and sometimes caused corrosion in moist environments such as industrial facilities that generated heat or steam, open-air roof framing, damp crawl spaces, weather exposure and other moist applications.

Hygroscopicity testing of FRTW in accordance with ASTM D-3201 is now required by building codes to substantiate low hygroscopicity.

Building codes and manufacturer's literature allow use of interior type FRTW in dry interior applications only, including plywood roof sheathing. Exterior type FRTW is for applications exposed to moisture, including direct weather exposure. These include exterior siding and trim, decks, balconies and stairways. Exterior type FRTW, like current interior fire retardant treatments, is non-hygroscopic and noncorrosive.

MYTH 2: FRTW is fire-rated.

Fire retardant treated lumber and plywood is often referred to as "firerated lumber" or "fire-rated plywood." Wrong. The "R" in FRTW stands for "RETARDANT", not "RATED." FRTW is tested for flamespread per the ASTM E-84 tunnel test, "Standard Test Method for Surface Burning Characteristics of Building Materials," for a period of 30 minutes (E-84 test duration for other building materials is only l0 minutes).

The 30 minute duration ofl the E-84 tunnel test does not equate to a 30 minute fire rating. Codes require the flamespread classification per ASTM E-84 to be 25 or less, which means the flame progressed only 250/o or less of the distance it traveled on untreated red oak wood in the same test.

Fire ratings (30 minute, t hour, 2 hour, etc.) are determined by ASTM E-l19 "Fire Tests of Building Construction Materials." This test exposes an assembly of materials (such as a wall or ceiling assembly) to heat and flame on one side. It tests for heat transmission, burn-through, structural integrity, and ability to withstand a fire hose stream. It is not a required test for FRTW, although FRTW can be used in appropriate rated assemblies.

MYTH bustible. FRTW is noncom-

In many applications such as roof systems on commercial and institutional structures, FRTW is accepted in lieu of noncombustible materials. FRTW is a "slow burning" building material, which is one category below noncombustible. For insurance purposes FRTW is usually rated as a noncombustible. It has a much slower rate ol

Story at a Glance

Expert blasts the myths surrounding fire retardant treated wood... what's the real story in six areas of FRTW.

heat release than combustibles such as untreated wood. FRTW produces little smoke, is self-extinguishing when removed from the flame source, and does not contribute to the spread of fire.

MYTH 4: FRTW is ruined if it gets wet.

Brief exposure to rainfall after installation does not ruin FRTW lumber or plywood. FRTW plywood, by definition, contains exterior waterproof glue. If it didn't, it could not withstand pressure treatment with waterborne chemi- cal solution. FRTW should be stored in a dry place at all times. It should be covered and protected from rain the day it is installed il possible. lf rained on alter installation, it should be allowed to dry before being covered with felt or roofing. The American Plywood Association makes nearly identical recommendations for untreated plywood in APA publication J20D.

MYTH 5: FRTW cannot be finished or glued.

Finishing or gluing of FRTW is easy as long as it is allowed to dry thoroughly. Kiln drying after treatment may not reduce moisture content to an acceptable low level for finishing or gluing. Exposure to air in a heated building for a week or two after installation is usually sufficient to allow moisture content to stabilize at an acceptable level for finishing or gluing. Consult FRTW manufacturers for more specific recommendations.

MYTH 6: FRTW disintegrates after just a few years of use.

New methods ol accelerated high temperature strength testing predict good performance ol FRTW products for decades in roof applications. A major U.S. model building code has issued the first FRTW code compliance report, on Pyro-Guard FRTW by Hoover, which includes evaluation ol high temperature strength testing and projections of strength properties after long-term use in roof, applications including plywood roof sheathing.

New strength testing methods and confidence in long term FRTW performance make it possible for FRTW producers to offer unprecedented warranty coverage. For example, Hoover's Pyro-Guard FRTW warranty includes 20 year replacement coverage at current cost. Another company's warranty provides longer coverage for plywood, reimbursing original cost of the roof if the plywood fails.

FRTW is used primarily in commercial, institutional and multifamily residential projects for roof sheathing, trusses, joists, studs, blocking and similar uses. Although the overall volume of building is down in many areas at this time, FRTW use is increasing as building officials and architects call for it more often.

Many market areas are wide open and begging for increased FRTW distribution and promotion. Economic conditions have forced some dealers out of business, creating opportunities for other dealers to pick up new business now and be in position to participate in the next building boom.

Code compliance reports available on FRTW include evaluation of high temperature strength testing for roof applications. Local building officials with the authority to approve individual FRTW brands often rely on these reports which contain strength factors and use recommendations for a specific product.

FRTW is stronger than ever.

Architects, building officials, contractors and owners, more aware of test methods and production controls that assure dependable performance, are specifying FRTW more often. FRTW warranties which provide long term replacement coverage not available with other building materials are a bonus.