How to Protect Your OSB with Waterproofing: Tips for Keeping Your Home Dry and Secure

Waterproofing OSB (Oriented Strand Board) is an important step in any outdoor building project. While much of OSB is made of wood particles held together by resin and is considered water-resistant, an extra layer of protection can ensure that your project won’t succumb to the elements. To waterproof your oriented strand board before starting your building project, follow these steps.

First, check that your OSB is stamped with the phrase “waterproofed,” indicating that it has been treated to be resistant to moisture. Even if your OSB does not have this stamp, you’ll still want to add an extra layer of protection for longevity. Lay the OSB on a tarp to protect it from dirt and grass, and measure and cut all the pieces you need for your project. Set them aside and keep a scrap piece from this step for later testing.

For added protection and a splash of color, consider applying a high-quality exterior paint to your OSB. If this is the route you plan on taking, make sure to do this before coating it with waterproofing. Sand the surface lightly to rough up the existing sealer and increase adhesion, then brush on your oil-based or latex-based paint. Let each section dry before flipping the pieces or adding more layers.

When you are satisfied with the look of your paint job, it’s time to apply a waterproofing sealer. Choose a sealer that is made for wood, as multi-surface sealers may not be suitable for OSB. Using a paintbrush, brush your sealer entirely over the OSB pieces, making sure that all sides —including the edges—are coated. Let the sealer dry for 12-14 hours, then flip the wood and coat the other side. You may need to add 2-3 more coats so the wood is fully saturated and ready for outdoor use.

To test the success of your waterproofing, pour a little water on your scrap OSB from earlier. Let it sit for a couple of hours and if the wood has not absorbed the water, you know that you have achieved a good layer of protection.

With these steps, you can confidently waterproof your OSB to protect your outdoor projects. Not only will this help to keep them looking pristine, but it will also ensure that they are durable and last longer.