Protect your plywood from dreaded delaminating

Plywood is a very commonly used material for both residential as well as commercial projects. Many DIY woodworkers prefer to use plywood because it is easy to build and to assemble with, apart from the fact that it is really affordable when compared to other materials. Plywood is also used for underlayment purposes, for siding, and even for subfloor installations.

Considering all these applications, it is important to appreciateĀ the longevity of plywood. Unfortunately it is a known fact that plywood is susceptible to moisture. Should it come into contact with water or moisture over time, it could easily start to deteriorate and the laminations with split. This is because it will start to rot, develop mould and destroy the adhesives that hold it together. Therefore it’s important to waterproof plywood sheets so as to avoid this from happening, while also increasing their life expectancy considerably.

Plywood showing early signs of water penetration. Image credit: Angie’s List

Since plywood is a laminated material, it accepts waterproofing easily. Plywood is basically made by gluing layers of wood together and then it is finished by applying veneer. Plywood is in fact comprised of several different layers of veneers which are glued together at right angles. As there are several layers, this leads plywood to end up being more vulnerable to water and moisture damage. Should plywood be exposed to water, the glues will end up disintegrating. As the wood will begin to rot, the layers will peel away from each other overĀ time. Thus, waterproofing plywood is critical.

Waterproofing with latex & oil based sealants

There are various types of waterproofing that can protect plywood. The most common type is the paint or spray-on liquid latex. Another form of plywood sheets waterproofing is by using penetrating oils and sealers.

Before applying the waterproofing material it is best to wipe the sheets and sand them. When wetting the plywood sheets, its grain will raise slightly. Then when the surface dries, it is important to sand the sheets lightly using a 100 or 200 grit sandpaper, in order to sand that grain back down and get a smoother surface for the waterproofing material to be applied on more effectively.

There’s many plywood waterproofing products on the market. Image credit: homedit

Flip the plywood panel over so as to apply the waterproofing material onto the other side. It is also very important to apply the waterproofing to all of the edges of the plywood sheet as the aim to create an impermeable surface. In fact the edges tend to be more exposed and they may naturally end up wicking up water. As a general rule of thumb it would be best to apply several coats of the waterproofing material, until it seems that they can take no more. Allow the solvents to evaporate between one coat and another. Generally three coatings tend to be enough.

As soon as the liquid latex dries up it will look and feel just like plastic. This is the protective layer which will safeguard the plywood sheets from moisture, water and other elements as well.

When the paint is used, it can be applied quite easily by using a roller. In fact rollers facilitate the process considerably. One can also use a brush too. In case of the spray-on option, it is best to use an electric sprayer that is used for paint in order to facilitate the application process, as well as ensure an even application. If you will be using a waterproofing material such as linseed oil, this can be applied using a brush or even a rag. With an oil-based waterproofing material, brushes tend to offer the best possible coverage.

It is best to use sawhorses so as to keep the plywood sheets at a reachable level. It is also best to carry out this waterproofing process outdoors since there will be fumes present. When one is outdoors the fumes will evaporate quickly.

Plywood is a very good building material, and it is also a very cost effective option if you were to compare it with other materials. However it is really important to waterproof it. Even though there are different grades of plywood, with different glues that hold the veneers together, they all tend to be susceptible to moisture. They will have varying degrees of water resistance, but it is still highly advisable to have them undergo the waterproofing process as this will greatly help in increasing the lifetime of the plywood. This will significantly prolong the useful life of what you will be building with the plywood sheets, especially if you are aware that these will be placed in a place where water is present. Plywood can even be used outdoors if it has been properly waterproofed. Speak to your local plywood supplier who can help advise you on the best grade and thickness of plywood for your next project.