Waterproofing Plywood: 3 Ways to Protect Plywood

Plywood is an excellent material that is used in different types of construction. From building homes to creating decks to crafting particular items, plywood is relatively inexpensive, durable, and comes in different types that are flexible for your needs.

One disadvantage is that most plywood is not waterproof. While there are certain types that are water-resistant such as marine plywood, all plywood will need some type of waterproofing if you want to protect it from the humidity.

The benefits associated with sealing plywood include the following.

  • Protects from Humidity and Ultraviolet (UV) Rays
  • Inhibits the Rotting Process
  • Reduces Splitting

Even if the plywood is not going to be exposed to the elements, the benefits of sealing are strong enough that it should be used in most circumstances. The following demonstrates the best methods for sealing plywood.
waterproofing plywood

Best Methods of Waterproofing

There are several different methods of waterproofing that can be used to protect plywood. You should choose the one that best suits your needs. Keep in mind that you can do the work yourself or hire a professional. Depending on the size of the job, you may want to get professional assistance to ensure that it is done right.

Otherwise, if the area to be covered is relatively small, then you can do the work yourself by using one of the following methods.

Epoxy Sealing

This is a popular type of sealant that can be easily used on most plywood. The advantage of an epoxy sealing product is that it protects the wood while allowing it to retain its natural color. Plus, the epoxy itself is quite strong and can be used on plywood that is both indoors and outdoors.

Smith's Clear Penetrating Epoxy Sealer [CPES]

To prepare the plywood, you will need to sand the surface to remove any dirt, debris, and loose particles. Then, apply the epoxy sealant as per the instructions. This usually means applying the epoxy in an even layer while it is still in a liquid state. Once the components of the epoxy meet, they tend to dry and harden quickly to create a protective layer on the surface of the plywood.

One substantial advantage of epoxy is that the forms a hard, durable layer that is stronger than paint or hard oil. This means that it can resist the elements for a long time. Plus, it can be reapplied without having to remove the older layer of epoxy, unlike paint. If there is a downside, it is the limited variety of epoxy in terms of coloring or tinting the plywood.

Penetrating Hard Oil

This is an oil that as the name implies penetrates the surface of the wood which seals it against intrusion by moisture. The oil itself can be applied across the surface of the wood evenly and allowed to soak in to seal it up.

SEAL-ONCE Marine water-resistant penetrating oil

You should use a penetrating oil that is designed for the wood itself. This means one that is meant to be used for waterproofing and keeps the wood moist enough so that it retains its flexibility and strength. You can start by sanding the surface to remove any loose particles, dirt, or debris. Once sanded, apply the oil in an even layer.

Depending on the type of penetrating oil used, you may need to add another coat once the surface has dried. The oil is best used on plywood that is not exposed to the elements. While it does offer some protection, the constant wind, sunlight, and exposure to moisture will dry out the oil that is near the surface over time.

This means that you should use penetrating oil on plywood that is not going to be outdoors unless you want to reapply it frequently. Although it may be easier and less time-consuming than paint or a spray epoxy, the oil itself will need to be reintroduced far more frequently unless the plywood itself remains out of the elements.

Paint or Spray-On Latex

Painting is one of the most common methods of sealing plywood and one of the most cost-effective. Polyurethane or latex bases paints provides a layer of protection that seals the porous surface. But just as importantly it can decorate the plywood if the exterior is going to be seen. You can paint a deck, wall, or other objects that are crafted from plywood.

You must prepare the surface by sanding it smooth. This helps the paint to attach to the wood and create a smooth surface which is quite desirable both in visual terms and texture. Plus, sanding will remove any loose particles of wood that might detach after it has been painted. Once the sanding process is complete, you can apply the first layer of paint, use a primer, or apply spray-on latex.

Polyurethane water-resistant coating

Spray-on latex is essentially the same as paint as it provides a layer that sticks to the surface which seals up the porous plywood. If the plywood itself is not going to be seen or directly exposed to the elements, then a couple of coats of spray-on latex may be enough. Otherwise, you can use the product as the first coat, let it dry, then add a layer of paint over the top.

Waterproofing stain for plywood

Once you have completed painting the plywood, you will need to add a new coat from time to time depending on the wear it receives. When the time comes to repaint the plywood, you will need to strip the old paint away first, sand the surface again, then add at least two coats of new paint or spray-on latex to do the job.

Painting or spray-on latex is generally best for surfaces that will be directly exposed to the elements. This means that the plywood is on the outside of the home such as a deck. However, painting can be used in most situations involving plywood as it is relatively inexpensive, versatile, effective, and long-lasting.

Waterproofing plywood is relatively straightforward. You simply need to choose the method that works best for your needs. Keep in mind that the waterproofing process does take time and effort. Plus, it will need to be repeated from time to time for maximum benefit.