To keep moisture out of plywood, seal the porous end-grains, coat all surfaces with a waterproof membrane (like epoxy or polyurethane), and maintain good airflow in the surrounding area.
Drying the Plywood
To waterproof plywood, start by selecting exterior-grade or marine-grade wood. Sand the surface smooth, thoroughly seal all exposed end-grain with exterior caulk, and coat the entire sheet with a heavy-duty waterproofing membrane, epoxy resin, or multiple layers of exterior spar urethane.
Moisture is drawn out of wood through evaporation, which is driven by an environment that features warm temperatures, low relative humidity, and active airflow. The drier and warmer the surrounding air, the faster it will absorb the moisture escaping from the wood fibers.
Untreated, uncoated plywood is both a hygroscopic and an anisotropic material, like wood. Hygroscopicity means that wood absorbs moisture from the air, making the dimensions of plywood change as moisture is transferred within the cellular structure of the wood.
Epoxy. Epoxy sealers are usually the preferred method of sealing and waterproofing plywood. Epoxy doubles as an adhesive, which gives an additional layer of strength plus protection for the wood, helping it to last even longer.
No, standard wood stain does not make plywood waterproof.
Epoxy Resin
Epoxy is a two-part system: resin and hardener. When you combine them, a chemical reaction will change the liquid into a tough, totally waterproof finish. It completely seals the wood, filling every pore and creating a surface that water literally can't penetrate.
Yes, baking soda does absorb moisture from wood. It acts as a natural desiccant and can be sprinkled on damp areas to draw out humidity. However, it is primarily effective for surface-level moisture and should be used with caution to avoid damaging the finish or causing stains.
The jar of petroleum jelly or Vaseline that you have in your medicine cabinet can work wonders to remove white water rings from furniture. The oily petroleum base penetrates the finish on the wood, displacing the moisture trapped inside, and the oils also nourish and condition dry wood.
Waterproofing plywood generally requires penetrating sealers or thick elastomeric coatings rather than standard aerosol sprays. For best results, choose a high-quality product that penetrates the grain or forms a heavy-duty, protective membrane.
Plywood can typically withstand rain exposure for a day or two without significant damage, depending on the type of layered wood and the severity of the rain. However, long-term exposure can lead to serious damage such as warping, cracking, or rotting.
The most affordable way to waterproof wood is by starting with a natural wood oil and following with a coat or two of outdoor paint. Though more budget friendly in the short term, you will need to redo this method more frequently, as it is not as long lasting as, say, a pricier, high-quality sealant.
To kill mold instantly on wood, use distilled white vinegar or hydrogen peroxide. These solutions kill mold at the root without damaging the wood's structural integrity.
It would definitely dry the wood. You would need 200 proof or anhydrous alcohol. On the downside, it would also remove unintended chemicals from the wood and it would become brittle.
To dry a wet plywood subfloor, stop the leak, remove any standing water, and maximize airflow. Crank up your indoor heat, run a heavy-duty dehumidifier, and use commercial air movers or box fans to circulate air directly across the damp plywood.
Acidic vinegar, particularly when used with baking soda, can wear down the rubber seals on your pipes. It's not just your actual pipes you have to be cautious of when unclogging drains.
Moisture is drawn out of wood through evaporation, which is driven by an environment that features warm temperatures, low relative humidity, and active airflow. The drier and warmer the surrounding air, the faster it will absorb the moisture escaping from the wood fibers.
Yes, you can absolutely mix Dawn, vinegar, and baking soda. This combination is a highly effective, non-toxic DIY cleaning trio. The grease-cutting power of Dawn, the acidity of vinegar, and the mild abrasiveness of baking soda make it perfect for tackling tough grime, soap scum, and baked-on messes.
OLYMPIC WATERGUARD for Wood Waterproofing Clear Sealant offers convenience and value. A penetrating clear sealer that protects the wood while allowing the wood grain to show. Perfect for multiple wood surfaces.
Coal-tar creosote
Creosote was the first wood preservative to gain industrial importance more than 150 years ago and it is still widely used today for protection of industrial timber components where long service life is essential.
No, you should not use WD-40 to seal wood. It is a petroleum-based penetrant and lubricant, not a wood sealer. Using it on wood will leave a greasy residue that never truly dries, attract dirt, seep into the wood grain, and permanently damage or ruin future paint or stain jobs.
The cheapest way to effectively waterproof plywood is by sealing the vulnerable end grains with exterior caulk or waterproof wood glue, then applying 2-3 coats of exterior oil-based primer and high-quality exterior latex paint. This method costs approximately $15−$35 per gallon and utilizes basic supplies.
Yes, absolutely. Many exterior and specialty wood finishes are "stain and sealer in one," which add color while providing a water-resistant or waterproof barrier.
The best stains for plywood are gel stains or fast-drying oil-based stains. Because the soft grain of plywood absorbs liquid stains unevenly, resulting in a splotchy look, gel stains sit on the surface rather than soaking in. This creates a beautifully uniform, rich, and streak-free finish.