When building residential wood structures, a good home builder will invest a lot of time in choosing the materials that will best serve future homebuyers. Building or renovating a home, shed, cabin, or another structure is a challenge when it comes to weather delays. If you’re using OSB, you’re probably wondering, is OSB waterproof?
OSB is typically made with industrial grade adhesives that seal and bond the individual wood strands together. In addition to the adhesive, a water-resistant wax coats the wood strands for additional protection, making the panel more water-resistant than other panels. The edges are also sealed for further protection when the panels are sized at the mill. OSB is highly water-resistant, but not waterproof.
Today, we’ll explain what OSB is, why it is water-resistant, and how to make it more waterproof.
WHAT IS OSB AND HOW IS IT MADE?
Oriented strand board (OSB) is a type of engineered wood that constitutes a cross between particleboard and plywood. OBS is formed by adding strong adhesives (wax and synthetic resin adhesives) and then compressing multiple layers of wood strands (flakes) into specific sizes of material. For the longest time, there were few alternatives to good plywood. In recent years, the builder use of oriented strand board, or OSB has gained in popularity.
From a structural standpoint, OSB is at least as strong and durable as plywood. On the downside, OSB is a bit more expensive than both particleboard and plywood simply because of the cost of materials needed for the manufacturing process. Also, the manufacturing process itself takes more time, which adds to the cost.
Is OSB Plywood Water Resistant?
The finest OSB is created by compressing and gluing wood flakes together to form a strong and durable surface, OSB panels have no structural internal gaps or voids. At a very basic level, it makes OSB naturally water-resistant. At the same time, it is impermeable because of the need to also create membranes for additional structural strength.
The use of waterproof resins and wax, the lack of voids, and the edge sealer make standard OSB panels water-resistant. However, all cuts should be painted with an appropriate sealer to prevent moisture from being absorbed.
Because OSB has impermeable properties, it is water-resistant to a point. From a practical standpoint, it would be water-resistant enough for an interior building project where the only real exposure to moisture would come from humidity in the air. That being said, OSB is not recommended for exterior building projects without the addition of other waterproofing materials.
How to Waterproof OSB
OSB is a great alternative to plywood. OSB is thicker than plywood and therefore stronger. You can use it for floors, roof trim, wall sheathing and even furniture. . The manufacturer waterproofs the board before selling it. However, before crafting furniture or other items, you may still want to waterproof them to provide additional moisture protection and ensure durability. This is especially important for outdoor applications of OSB.
Selecting an OSB product that is stamped WATERPROOF is a good start for a waterproof finish. It is not difficult to do your own waterproofing, but you do need to follow the right procedures. Several coats of quality exterior grade primer and porch paint or stain will help waterproof standard oriented strand board panels. Covering the OSB with a weather-resistant material and siding, bricks or shingles will also protect OSB from precipitation.
Make sure that you plan carefully before cutting the boards.Sealing all cut edges ensures moisture is unable to penetrate wood that wasn’t pretreated with waterproof resin adhesive during manufacture. Cut or untreated edges are more likely to swell and even delaminate if exposed to moisture. Sealing prior to installation improves the waterproofing and protects the structural integrity of the panel.