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Waterproof Plywood Sheets

How to Waterproof Plywood

The Importance of a Waterproof board

Why waterproof plywood?

Compared to solid wood, plywood is much cheaper and more durable than chipboard or MDF. Yet it is visually pleasing enough to be used for furniture.

Plywood is made by glueing and compressing layers of veneers in opposite directions. This helps create a structurally strong board and helps keep the board as flat as possible.

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 can also be purchased in a sealed and treated state to save the effort of manual waterproofing. If you still need to buy the plywood for your project, this is often a cheaper and easier solution.

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Common problems with unprotected plywood.

Why Should you Waterproof Plywood?

Like other natural materials, untreated plywood is susceptible to rot caused by moisture and water, creating a breeding ground for fungus or mould within the board. As the wood rots, it affects the board's integrity, which can cause it to break down over time.
Plywood delamination
Plywood delamination
The plys within the board are created by glueing and pressing. Although good at adhesion, the glue used is not generally waterproof. If the glue disintegrates, the plys will pull apart, causing irreparable damage.
Weak Spots
Weak Spots
When you cut plywood, you expose the edges. Plywood edges are weak spots because they absorb moisture much quicker than the surface. It is essential to make sure you seal plywood edges to protect the board.

Prevents warping
Prevents warping
Another situation you'll find yourself in if you don't correctly waterproof plywood is that there is a possibility of the board warping. Water damage causes plenty of materials, such as timber or MDF, to warp, so make sure you only use bone-dry waterproof plywood sheets before sealing.
Longer lasting
Longer lasting
Sealing the plywood edges and surface properly also gives your material a longer life, and continuous application throughout the life of your furniture or project will keep it looking good and protected, no matter what life throws at it.
Applying a good sealer will make your plywood surface look remarkable and transform birch plywood into something similar to oak or walnut.

Before you begin

How to Prepare Plywood for Waterproofing

Fill holes and lightly sand the plywood with coarse sandpaper to remove blemishes and provide a surface that will help any varnish or sealant properly adhere. Wipe down the surface to be free from dust particles and ensure the edges are smooth and even. Then, you can apply a waterproofing agent using spray-on or paint-on methods.

We advise only trying this on plywood cut with proper machinery for best results. Professionally sized cut boards offer a much cleaner base to work from and, as a result, can last for longer.

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The Best Sealant Options for Waterproof Plywood

A hardened finish for protection

Latex paint

Latex-based or polyurethane-based paint is one of the most accessible forms of waterproofing plywood. There are plenty of colours to choose from, which can be applied using a spray gun or painted with a roller. You must apply two to three coats of paint for maximum effectiveness. Latex paint is also one of the cheapest methods. However, you will need to repaint it often. You can use latex-based for indoor or outdoor projects. A waterproof board with latex-based paint can give it a lovely, complex finish, but you will lose the natural aesthetics.

Simple and effective

Lacquer and varnish

Lacquer and varnish as a sealant are perfect for waterproofing wood sheets for indoor and exterior use. They can be applied using a brush, roller, or spray to achieve a finish to your liking. Polyurethane varnish and lacquer make the natural veneer grain more prominent, giving you that natural look. Using varnish and paint to seal plywood provides not only an enticing colour but also water protection and UV protection; however, there is a possibility that this type of sealant can turn yellow over time. 

When choosing your lacquer or varnish, find one that matches the plywood veneer you're working with to give you the best results after sealing.

Deeper protection

Wood oils

If your project is used indoors, you could use wood oils. Due to the porous nature of wood, the oil penetrates and soaks into the surface veneer. This type of sealer gives the wood a natural look and can be applied by painting on or using a cloth to rub the oil into the wood. You must apply 2-3 coats of oil, as the plywood will fully absorb the first coat.

Shelter from the elements

Epoxy sealant

This type of sealant works best for outdoor projects as it offers more protection. The best thing about an epoxy sealant is that you only need one layer to get the best waterproof protection for plywood. Depending on the type of epoxy you use, you will have a finish that retains the natural colour of the veneer, or it will slightly tint it. You can apply this sealant using a paint roller or brush, ensuring you keep the strokes even throughout.

Cheap and easy

Water-based paint

Another cheap method of sealant is a water-based paint. This sealing method is less standard than it's less long-lasting than the other methods. This paint may also need to be touched up more often, but it is cheap, quick and protects your plywood from moisture.

It's worth mentioning that it is not advisable for water-based paint to waterproof plywood for outdoor use, as the harsh elements, either UV rays or continuous rain, will wear down the paint within a few months.

Alternatively, let Cworkshop do all the hard work for you. Send us your project details, and we'll waterproof all your wood on your behalf.

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More than one option of plywood.

Waterproof Marine Plywood

If you're looking for the plywood that you're confident, even after sealing, will have the most protection against water and moisture, then you should consider marine-grade plywood. Marine plywood is a type of plywood that is more water-durable than regular plywood. The glue used to stick the veneers, or ply, is waterproof, which means it won't de-laminate when exposed to moisture or water. 

Waterproof marine plywood also has no gaps between the plys. Gaps weaken the overall structure of plywood and create a path for water or moisture to get inside the plywood sheet, which can cause the board to weaken from within. The surface veneer of marine plywood is from a wood that can withstand the elements, thereby giving your plywood a longer life.

As the name suggests, marine plywood is used in boat building. Not only does it have excellent waterproofing capabilities, but it's also hardwearing and can take on impacts like a pro boxer.As the name suggests, marine plywood is often used in boat building. So, not only does it have excellent waterproofing capabilities, but it's also hardwearing and can take on impacts like a pro boxer.

One of the reasons why plywood is often used is because the edges provide a lovely effect. If this is the main reason for using plywood, then you should consider getting melamine-faced plywood, which means you will only need to seal the edges rather than the entire plywood sheet, thereby saving you time.

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Make it easier for yourself.

Get Professionally Waterproofed Plywood Sheets

Cworkshop can guarantee waterproof plywood, freeing you up to concentrate on creating beautiful designs for your clients.

Need to know more about waterproof plywood?

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