October 5, 2020 by Curtis Lumber & Plywood. Six weeks ago my builder put in the floor joists and the wood subfloor. Some varieties will be given a special treatment to control dampness, which can offer dual protection. I'm getting oak flooring installed over this junk wood. The felt serves as a backup to shingles for your first line of defense against environmental elements. Below is a closer look at the most important considerations. If you want to ensure that your construction project will offer maximum safety in the event of a fire, consider hiring a company that specializes in fire-retardant plywood. This kind of moisture is what you’ll find on the bathroom walls after a super-hot shower. Subscribe to the FREE Ask the Builder newsletter to receive professional advice for your home. DEAR RICHARD: I am at a little disadvantage since I can't see the wood. ... they are only using plywood as they had the issue in a new construction project and the price of remediation and the stigma of “mold” put on the house cost them a lot more than the difference in price between the two materials. Some types of fire-retardant plywood can indeed get wet. Products carrying the Exposure 1 stamp are designed so that minimal damage will occur during normal construction activity. Will the oak flooring be fine over the OSB? Wait it out. Condensation occurs when hot, moist air hits cold, dry air. This is one reason I like sheathing my houses with a base course of PT Plywood 2" around the bottom course of sheathing then going up from there with OSB (or plywood if the budget can take it). My houses are somewhat large, and it is not uncommon for the plywood to get rained on since it takes 4-5 days to deck them, they sit for 2-3 days before roofer can get on the job, throw in a weekend, there is a good chance they will be rained on. Even if the plywood is rated as exterior-grade and manufactured with water-proof glue, if water penetrates between layers, it causes them to swell and warp, pulling the layers apart. While the glue is waterproof, the wooden layers aren't, and they can swell or deform when exposed to moisture. The glues used to bond layers of wood in exterior-grade plywood and the strands of wood in exterior-grade oriented strand board (OSB) are made to resist water. DEAR TIM: I'm having a new house built. Manufacturers use particleboard because it is less expensive than plywood. The risk of warping increases and the rate of moisture evaporation decreases if damp plywood is left untreated. Trapped water will boil when the sun heats the roof and the shingles will then have small pits … Charring helps protect the wood from further damage in a fire, helping it to retain some of its structural integrity. What causes condensation? In such cases, the exact thickness of the walls can complicate final finishing work. When moisture becomes trapped in a subfloor, it can cause tiles to bubble and warp. Water-repellent preservatives can also be applied to this type of wood for applications that will give it direct exposure to water and moisture. But put fans on it, and under the area in the basement too. Immediately after the subfloor was installed, he framed the walls. Depends on the wood form and treatment or finishing done on the wood. In fact, most are waterproof. They can also be painted and stained. The vacuum created within provides the appropriate conditions for the flame-retardant chemicals to be added. The tear-off gets a lot more complicated if you have something other than asphalt up there: If you can see original wood shingles on the underside of your roof when you’re up in the attic, you’ll need not only to tear everything off, but also to install new plywood decking, all of which likely adds $5,000 or more to your costs. Use Fans 3. To ensure the plywood has been fully infused and will offer the expected benefits, the wood is then subjected to a series of quality control tests. Stacks of OSB plywood sheets. First by absorbing the water, then releasing it. Once the chamber has been filled with flame-retardant chemicals, the pressure is used to ensure the chemicals are fully and evenly infused into the wood. What happens if fire-retardant plywood gets wet? In addition, these products are dried in a kiln after treatment to guarantee their workable moisture levels. 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