What else can we do to wood? We’ve coated it with penta, soaked it in arsenate, injected it with copper, borate, quat, chloride, and chromium. We’ve dunked it in glycol under high pressure, coated it with glass, and even cooked the living daylights out of it in kilns. All of this is done to preserve our access to the most versatile, affordable building material that man has ever put to use: wood and wood fiber.
Next thing you’re going to tell me, someone has made wood fireproof! Oh, you mean that’s already been done?
All kidding aside, fire-proofing wood or making it fire retardant or fire resistant is nothing new, and it’s very serious business. Recent code requirements have brought fire treatments into the limelight, mostly because of the R501.3 Fire protection of floors requirement. R501.3 requires that floor assemblies be fire-resistance rated. The goal of the new code: To achieve “one-hour” fire resistance protection, so people can get out of a burning building before it collapses, or so fire personnel can safely get into the structure to put it out.
Not surprisingly, the wood products industry has offered some innovative solutions to comply with the code. One innovation is a treatment called intumescent coating. When an intumescent coating is applied to wood, and that wood is subjected to high heat (normally in the form of an open flame), the coating swells. As the coating swells, it increases in volume, yet it decreases in density. (Think of raw bread dough rising during the baking process). The high-volume, low-density coating frustrates heat transfer between the flame and the wood fiber, delaying or even preventing ignition. Practically speaking when you apply a coating like this to, say, an iJoist, it can help achieve the code-required, one-hour fire rating. Weyerhaeuser’s Trus Joist TJI joists are now made with Flak Jacket, an intumescent coating treatment. You can see some cool videos on YouTube that demonstrate the coating in action. One video shows an apple wrapped in the Flak Jacket coating. (It’s edible after the fire, and you wish the lab tech would take a bite.) The second video shows I-Joist webbing coasted with Flak Jacket, and it too survives perfectly well after six minutes of exposure to an open flame. There’s even a Christmas edition of the test, where the techs try to burn a candy cane and a Santa.
Intumescent coatings are not new (intumescent putty is a common commercial fire-stop), but we are now seeing some innovation applications of them in wood frame structures.
The next thing you know, they’ll come up with wood that holds paint.