OSB: OSB has a higher resistance to moisture compared to plywood. It swells less and retains its structural integrity better when exposed to water, though it should still be protected from prolonged exposure. Plywood: Plywood can be prone to delamination and warping when exposed to moisture over time.
Plywood is moisture-resistant, but it is not waterproof. It is important to seal plywood if it will be exposed to moisture. OSB is not waterproof, but it is more moisture-resistant than plywood. It is still important to seal OSB if it will be exposed to moisture.
OSB can be manufactured into panels that are larger than plywood. OSB is more uniform, so there are fewer soft spots, such as those that can occur in plywood. OSB is less expensive than plywood. To build a typical 2,400-square foot home, OSB may cost $700 less than plywood.
Though OSB is more moisture resistant than other wood products, it can still be damaged by moisture. Whether you're a general contractor, flooring installer, or woodworker, moisture damage in OSB panels could lead to costly repairs and crushed business reputations.
Mold and Rot Resistance
Plywood absorbs water faster than OSB but it dries faster compared to OSB. This could be a major issue, especially when used as material for new roof installations. OSB tends to puff up like a sponge when wet, especially around the edges. This happens because of the way it's made.
“The major disadvantage of OSB is that if it gets exposed to significant amounts of water or moisture, the edges expand by up to 15% ... especially if they are cut edges. This swell will then telegraph onto the shingles or some flooring," according to PATH.
Although the surfaces of the boards repel water, their edges are somewhat more vulnerable. Whereas moisture causes ordinary wooden boards to warp, OSB panels that become wet or moist tend to swell at their edges.
Plywood is better in most cases unless the panels are exposed to water or moisture in which case plywood is BARELY any better. In applications where the panel is not ever exposed to water or moisture, OSB is nearly as good.
There are three main methods we recommend for making OSB waterproof: sealants, waterproof paints, and waterproof membranes. Each has its advantages, and the best choice depends on your specific application.
Marine plywood is recommended for any plywood application where the timber will be directly immersed in water for a period of time such as boat building and other marine activities. In most instances though, an external rated ply is a suitable alternative for applications requiring general moisture resistance.
Both plywood and OSB are effective choices for your subfloor needs, but OSB may be a better option for a garage than plywood. Plywood is a better option for projects that require a lot of cutting and molding, while OSB is a good option for those who need to cover areas where moisture exposure may be an issue.
Since OSB is a cellulose-based material, most of the time it already contains mold spores and only requires moisture to trigger the growth process.
Environmental Impact: OSB's manufacturing process utilises smaller, fast-growing trees, which could be considered more sustainable. Ease of Installation: Both materials are relatively easy to install, with plywood being slightly more forgiving due to its ability to hold screws along the edges better.
The way that OSB is manufactured makes it more sensitive to moisture than plywood. However, the price point of OSB sheathing is typically more affordable and therefore has become the sheathing of choice for North American builders.
Ideally we'd have no vapor barrier in summer; but short of that we should at least have one that allows as much drying to the interior as possible without sacrificing its winter performance. So the closer your vapour barrier is to 60NG, the better.
Unlike other wood-based materials, plywood isn't fully waterproof. Still, the good news is that you can produce waterproof plywood, thereby giving your furniture a longer life. You must seal your plywood, mainly if used in high-moisture areas such as bathrooms, kitchens, or outdoors.
Plywood: Which is more water-resistant? Plywood absorbs moisture faster than OSB, but it also dries out more quickly, and it isn't prone to edge swelling.
Using OSB Safely
When installing in vertical applications such as wall sheathing, you'll want to orient the smooth or stamped side facing out. The smooth side has a better moisture resistance and will ultimately provide better performance against weather.
If you nevertheless choose to do so, make sure to use only solvent-containing polyurethane- or synthetic resin-based products. Other coating systems only yield satisfactory results on sanded boards. Virtually all coating products that can be used on solid wood can also be applied to sanded OSB.
There are no advantages. OSB is highly susceptible to water damage, is not as strong, is heavier, and more slippery than plywood. It is almost the same cost per sheet as the equivalent strength plywood. Plywood, per thickness, is stronger, water resistant, and lighter than OSB.
OSB is not waterproof or water resistant. Like most wood-based materials, OSB tends to expand and contract as moisture is wicked into and expelled out of wood fibers. The wood fibers exposed to the elements swell as they interact with moisture in the air and water droplets.
Strength. OSB and plywood are very similar in terms of strength, but plywood is stiffer than OSB by a factor of approximately 10%.
Here are some options to consider: Liquid-Applied Membranes: Liquid waterproofing membranes, such as polyurethane or acrylic coatings, provide a seamless and flexible barrier against water intrusion. These products can be rolled or sprayed onto the OSB board and create a durable protective layer.
OSB (oriented strand board) wall sheathing can generally handle light to moderate rain without significant damage, but prolonged exposure or heavy rain may lead to swelling, warping, or decay over time.
Panelvent DWD is a 12mm thick square-edged sheathing board designed to replace OSB and plywood as an external lining board to provide racking and enhanced vapour transfer for timber frames and conventional construction. It offers advanced moisture control and durable building protection.