Use of Coatings to Improve Fire Resistance of Wood

Currently used fire retardant coatings for wood products reduce flame spread; they are not designed specifically to provide fire resistance. Fire resistive coatings designed for steel and foam plastics generally are not recommended for wood. Small nonload-bearing fire resistance tests were conducted in this study to determine the fire resistance of eight commercially available fire retardant and fire resistive coatings when applied to a wood product.

Coated plywoods over a foam plastic substrate were tested in a small-scale vertical exposure furnace in accordance with ASTM Fire Tests of Building Construction and Materials (E 119-82). The results were the times for the temperature rise to reach an average value of 139°C (250°F) or a maximum value of 181°C (325°F) at the plywood/foam-plastic interface. Uncoated plywoods were tested as controls.

Fire retardant coatings improved the times for plywood specimens by up to 900 s, and fire resistive coatings showed a 240- to 2640-s improvement over uncoated plywood. Coatings significantly improved the fire resistance of a wood product. The fire resistance data reported in this paper should aid in future considerations of fire resistive coatings in wood construction.