Building materials greatly affect how and how fast a structure will burn. To stave off fast-burning fires, in the 1970s the plywood industry developed fire-retardant-treated (FRT) plywood for use in wood-frame structures. But the treatment damaged the wood’s structural integrity, and the sun unintentionally activated the fire-retardant chemicals causing a chemical reaction that began to decompose it, said Michael Huddy, president of International Barrier Technology Corp. Huddy said FRT on the market today still degrades upon treatment and in the presence of heat.

“FRT plywood is produced by taking plywood sheets and placing it in water-borne salts and then removing and pulling it out of the salts with a reverse vacuum system so it sucks water and salt into the fiber of the wood — right through it,” Huddy said. “When those salts get hot, it turns to acid. And the acid consumes the wood in a process called acid hydrolysis very quickly so it’s not available to burn and create more fuel to a fire and make it spread even bigger. So what FRT plywood is engineered to do is incinerate under heat.”

However, the processing makes wood lose its strength, according to Huddy. He said when it is treated it loses up to 15% of its strength. Overtime, those salts engineered to turn into acid in high temperatures can be activated by sunlight.

“The temperature gets up to 135°, there is a partial decomposition of the salt materials in the wood before you ever see a fire,” Huddy said. “So there are some inherent issues with using FRT plywood. No. 1, it loses strength quite quickly overtime. And in a fire, while it doesn’t provide much fuel to a flame spread, there’s not much in the sense of resistance.”

Huddy said in comparison, his Minnesota-based company has developed a viable alternative dubbed Pyrotite, a coating that is painted onto structural wood panels that offers a special barrier that comes between fire and the underlying wood. This layer has a molecular structure that contains a large volume of water, which is released only at about 475° F — just below the combustion point of wood — and serves to slow the spread of a fire. As a result, treated panels offer a lighter and stronger alternative to gypsum, another material that is commonly used to make wallboard fire-resistant, he said.

“We have a thin coating that we put on the surface, so we don’t impact negatively the strength of the wood. In fact, our coating is fiberglass-reinforced and makes the wood stronger, so it holds up well in earthquake and high-wind zones,” Huddy said. “We augment it by adding this layer of concrete, specialty cement to the wood. It is a non-combustible barrier between fire and the wood portion of the structure and it also contains 2 quarts of water every square foot of surface panel. The water only comes off as a steam vapor when fire hits it, and it heats up just before the wood might start to burn below it. So you have this vapor of steam that comes off and cools the fire.”

Underwriter Laboratories rated the panels for one- and two-hour applications with a zero flame spread index, Huddy said. Pricing was unavailable.