How To Stop Plywood Doors From Warping [A Complete Guide]

Plywood doors are an affordable alternative to wood and fiberglass doors. With their considerable stability and impact resistance, they are your best choice for an internal or garage door. But most plywood doors tend to warp when exposed to moisture. Fortunately for you, preventing plywood doors from warping is simple. How? We did the research to bring you the answer.

Waterproofing prevents a plywood door from warping, which will save you from costly repair costs in the long run. It only takes a few materials you can find in your local home improvement store. Here are three methods you can use:

1. Apply polyurethane to your plywood door.
2. Coat the plywood door with epoxy sealer.
3. Use water-based paint on the door.

Waterproofing is not as elaborate as its name implies as a means of stopping plywood doors and other plywood-based materials from warping. Depending on the method you choose, it'll just take a bit of time and effort. Continue reading to get into the specifics of each process. 

How To Keep Plywood Doors From Warping

Below we will discuss the methods of waterproofing a plywood door in greater detail. 

1. Apply Polyurethane To Your Plywood Door

Coating your plywood door with a polyurethane varnish is our top recommendation. Polyurethane varnish works like a protective shield by providing a super-tough layer of tightly bonded microscopic resins.

In effect, surfaces treated with this solution become water-resistant and less prone to abrasion and warping. This is the reason why varnish is used even on oak doors.

Read through our previous post to know the benefits of coating oak doors with varnish.

To apply, first remove the plywood door from the jamb. You have to lay the door flat to avoid leaving untreated areas. 

Three Ways You Can Apply A Polyurethane Varnish

• Using a paintbrush 
• Wiping the varnish on the door
• Spraying the polyurethane varnish

Using a paintbrush is the ideal way to cover your plywood door with varnish, as you can cover a wide area with more precision. With a medium-sized brush, apply the first layer of varnish protection on all the surfaces and edges of the door.

Wait for at least 30 minutes for the first layer to dry. You can check if the varnish has completely dried with a tissue, then apply the second coat. 

Wiping or spraying the varnish is also a quick way to apply the poly. However, a wipe application requires you to use a cloth that can absorb most of the varnish, while a spray-on application does not give you control over the application. 

But regardless of how you apply the varnish, the plywood can darken after application.

Check out this Varathane Water-Based Ultimate polyurethane varnish on Amazon.

2. Coat The Plywood Door With Epoxy Sealer

You can also prevent your plywood door from warping without worrying about color alteration. With an epoxy sealant, you can shroud the plywood door with anti-warping capability while retaining its color. Plus, it will also strengthen the outer layer of the plywood. 

Before applying epoxy, ensure your door is clean and in good condition. Sand off the door first to remove accumulated dust and gunk. This will enable faster and better absorption during application. 

Equip yourself with protective gloves and a mask first to protect yourself from the toxins of epoxy. Paint the epoxy in stable strokes on the surfaces and edges of the plywood.

As epoxy tends to harden fast when it meets other materials, you should immediately spread the chemical with haste upon contact with the wood. For faster application, you can use a small, thin foam roller. 

With epoxy, you no longer need a second coat in most cases. You only have to wait for it to dry, and then you can already install the door back. 

Check out FGCI Premium clear cast epoxy on Amazon.

3. Use Latex-Based Paint On The Door

If you want your plywood door to have both protection against warping and a striking appearance, then coating it with latex-based paint will be your best option. 

Latex paints are cost-effective dual-purpose material for sealing plywood. It blocks off the large pores on plywood, preventing water penetration. 

To apply the latex paint, make sure to sand off the door first to ensure the paint adheres to the wood thoroughly. Then, smear a single coat of primer as your first layer of pore sealing. This will also allow the paint to better stick to the plywood later on.  

Doing the right preparation keeps you from worrying about the wood grain negatively affecting the paint absorption. 

Similar to polyurethane varnish, you can also use two layers of spray-on latex paint after the primer. But we suggest only using a spray-on latex when the plywood door is meant for interior usage. 

Also, you have to be extremely picky with the paint to use, as some latex-based paints do not perfectly negate the possibility of warping. 

Check out this Kilz waterproofing paint on Amazon. 

How Do You Straighten A Warped Plywood Door?

Warped plywood doors are a pain to treat. That is why you have to straighten or flatten the warped surfaces or edges first. 

Follow the quick and easy fix below:

1. Spray hot water on the area where the warping occurred, specifically the side or edge that shows the concave part. 

2. Lay the door in a place with a good flow of hot air. The area you sprayed water on should face downward, then put a heavy material on top. 

3. Leave the door under the sun and wait until it flattens. 

4. To finish the treatment, bring the door to a cold area in your house, such as the basement. 

And that is how easily you can bring back the natural state of your warped plywood door. 

Will Painting Plywood Keep It From Warping?

Painting plywood can keep the door from warping. Painting remains the most common way to seal the large pores of plywood that, when infiltrated with water, causes the door to warp. 

Keep in mind, though, that you should use water or latex-based paint. Water-based paints do not crack and peel off quickly when they completely dry compared to regular paints. There are some paints marketed to be waterproof today, so you can check those out.

But these paints do not guarantee 100 percent waterproofing. Thus, there is still a slight possibility for the door warping. Fortunately, you can avoid this.

Apply a primer before the paint and a sealant on top of the paint. Another option would be mixing a waterproofing additive to the paint to increase its warping protection. 

Can You Seal Plywood For Outdoors?

Are you planning on using a plywood door for your garage or equipment storage doors? You’re in luck because you can seal the plywood for these outdoor uses. So even when the plywood is exposed continuously to the elements, you can reduce the chances of splitting and rotting.

By applying drying oil to the wood, you can seal the plywood for outdoor use. The method is so effective that it is used to coat the wood at docks. 

Treat The Plywood Door With Drying Oil

Commonly used for marine and outdoor use, drying oil provides wood surfaces high moisture defense. It soaks deep into the pores of the wood itself to form a thin yet effective protective coating. As a result, woods become waterproof and dirt-resistant.

Applying the drying oil is straightforward and does not require you to have a pre-treatment solution. You only have to sand off the plywood beforehand to even out and smoothen the surface.

During application, you only need a brush or rag to wipe the oil on all the surfaces of the plywood door and let it soak into the wood by itself. 

Depending on the quality of the drying oil you apply, it may take about 3-4 coatings to achieve the desired finish and protection. Sanding in between each coat may also be necessary. 

But one disadvantage of drying oil is that you have to apply the oil more often compared to varnish and paint. 

Check out SEAL-ONCE MARINE wood sealer on Amazon.

What Plywood Is Least Likely To Warp?

Don’t want to trouble yourself with the listed steps above? Do you find plywood sealing exhausting and tedious? Well, why not choose a plywood door that is less likely to react to moisture and warp in the first place?

Plywood engineered from Douglas fir wood is least likely to warp since it is for interior and exterior use. As such, they can withstand the effects of weathering and possess a certain level of resistance to shrinkage, swelling, and warping. 

They come in three basic grades, namely AB, BC, and C. But if you are looking for the top-performing Douglas fir plywood, then it’s best to choose the marine grade ones, as they are the most powerful and water-resistant. 

In Closing

You are now already fully aware that you can stop plywood doors from warping. By simply applying varnish, epoxy sealer, or latex-based paint, you can make them less vulnerable to moisture and warping.

You can also further increase its resistance using drying oil to make your plywood doors better suited for the outdoors.

You might also want to know if oak doors warp. Our previous post has all the details you need:

Do Oak Doors Warp? [And Tips On How To Prevent Warping]