Plywood is a fantastic building material, as it can be used for a wide variety of purposes. That said, to be useful, it needs to be flat and straight. There’s just not much you can do with a warped piece. So, what do you do if you have warped plywood? How to flatten plywood is what we are going to cover right now.
There are actually quite a few methods for doing so, and today we want to cover them all.
Can You Flatten Warped Plywood?
The good thing here is that it is indeed possible to flatten warped plywood. However, you should first know why plywood is warped in the first place. Generally speaking, warping in plywood is caused by two things, heat and moisture.
A warped piece of plywood has two sides, the concave side and the convex side, or in other words, one side looks like a valley and the other like a peak, respectively. If you were to measure how much moisture is present in both sides, the outer veneers, you would see that the concave side, the valley, has less moisture. Because that side has less moisture, the wood veneers pull together, thus causing that warp to occur.
The good news is that there are quite a few ways to flatten plywood, both with just good old weight, as well as some other more specialized methods too, mainly ones that involve wetting and/or heating the plywood.
In addition to this article, you should also learn about how to prevent plywood from warping in the first place.
6 Ways to Flatten Plywood
We now want to take a closer look at the eight best ways to flatten plywood. Start with the first method, and if that doesn’t work, move on to the next, and so on and so forth.
1. Using Weight
If the plywood just has a small warp in it, you may be able to flatten it out with just some weight alone. This is going to work best for larger sheets of plywood that aren’t too severely warped. All you really need to do here is to lay the plywood on the ground with the convex side facing upwards.
You are then going to use a variety of heavy objects, really anything you have at your disposal, to weigh that plywood down.
You want items heavy enough to weigh the convex side down enough to the point where the entirety of it is resting flat against the ground. It may take a couple of days for this to fully work. However, if the warp is severe, this may not work, in which case you should try the following method.
2. Using Water and Sunlight
Another method you can use to flatten plywood is by applying some water and heat to it. Remember, with warped plywood, the convex side is too wet, and the concave side is too dry.
For this method, you first want to take a fairly wet sponge or spray bottle filled with water. You will want to thoroughly douse the concave side with water. You want those dry plywood veneers to absorb some water.
You then want to place that plywood somewhere outdoors, on a flat surface. You want the wet concave side to be facing the ground, with the hump facing upwards. You want to ensure that the plywood will be exposed to plenty of sunlight. The sunlight will help dry the side that is too wet, the convex side.
What you are doing here is wetting one side and drying the other, which should get rid of the warp. This could take anywhere from a few hours to a few days.
Now, if this doesn’t work, you may actually want to combine this method with the previous one we discussed, weighing the plywood down. You can wet the concave side, place it face down so that the convex side is in the sun, and then weigh the center down using a variety of heavy objects. Not only can this take care of more severe warping, but it will also help speed the process up quite drastically.
3. Using Water and a Hairdryer
The sun is great for drying out plywood. That heat can help a lot of moisture evaporate. However, maybe the weather in your area is not sunny, not very warm, or just not nice at all. If this is the case, you will need to find a different way to provide your plywood with some heat to help the moisture evaporate out of the convex side. This is where the hairdryer comes into play.
Just like with the previous method, you are going to use a spray bottle or wet sponge to thoroughly wet the concave side of the plywood. You will then place that side down on a flat surface. You will now take a hairdryer set to its hottest setting, and direct the heat towards the warped part of the plywood, the side facing up.
This may take quite a few minutes, but it should remove moisture quite quickly and effectively. Depending on the severity of the warp, this may however take longer. If this is the case, holding a hairdryer for hours on end is not ideal.
In this case, if you can rig up some kind of clamping system to hold the hairdryer in place while you take care of something else, then you are on the right track. Just don’t leave the hairdryer running unattended, as it can get very hot and pose a fire risk.
4. Using a Steam Clothing Iron
Another way to flatten plywood is by using a steam iron, yes, that same one you iron your pants with. For this method, you need to lay the concave side facing upwards. You will then weigh one side of the plywood down, right at the edge. This will allow you to keep it flat. You may also need to hold that side down with some additional force, your hands, or even some clamps. You will take your steam iron, set it to its maximum heat and steam setting, and you will then iron the opposite side.
So, if you weigh the right side down, iron the left side (with the concave side facing upwards). As you hold one side down, and then push the other side down with the iron, the combination of heat, steam, and weight should straighten the plywood.
5. Using Wet Rags
Yet another way to flatten warped plywood is by using a lot of wet and heavy rags. For this method, you are going to lay the plywood on a flat surface with the concave side facing upwards. You are then going to take a series of very wet and heavy rags, towels, and/or cloths, and wrap them around both of the sides.
The point here is to weigh down the ends of the concave side, and to wet them, which should bend those edges downwards, thus getting rid of the warp. Keep in mind that for this method, you only want the center of the plywood to be supported so that the outer edges can actually bend downwards.
6. Using an Orbital Sander
If the warp in the plywood is not very severe, you may not actually need to bend it back into its original shape. You may be able to just use an orbital sander to quite literally sand or grind the warp out of the wood. However, keep in mind that this only works for really light warping, as there is only so much material that you can sand away.
What Is the Best Way to Flatten Plywood?
If you are looking for the easiest way to flatten plywood, using method number two is recommended. Using some water, sunlight, and weight should do the trick just fine. If you don’t have an outdoor space, and it’s not warm and sunny, then either the hairdryer or steam iron methods should also work just fine.
It really comes down to the space and tools that you have at your disposal.
Mistakes to Avoid, Tips & Tricks
The trick when flattening plywood is to get rid of the warp without causing a warp in the other direction to occur. Follow the tips as outlined below to prevent this from occurring:
- If you are using water to flatten plywood, make sure that you don’t oversaturate the side being wet down. Getting that side too wet may result in the warp then going in the other direction.
- The same thing can be said for heat. If you are drying out one side of the plywood, drying it out far too much may also cause a warp in the other direction to occur.
Summary
Now that you know what all of the different methods for flattening plywood are, you can choose the one that you think will work best for you.