Plywood is of course a very common and useful building material. With that being said, it is not without its problems, especially specific types of it. One issue that some types of plywood have is that they are prone to warping. Of course, a warped piece is not going to be very useful at all.
For this reason, today we are going to provide you with some tips on how to prevent plywood from warping. We’re also going to talk about some specific types of plywood that are less prone to warping, as well as how to prevent this issue from occurring.
Why Is It Important to Prevent Plywood from Warping?
There are a few different reasons why you definitely want to prevent your plywood from warping.
First and foremost, warped plywood just doesn’t look very nice. If the plywood is warped, it’s going to be all bent and crooked, and nobody wants that on the exterior of their home or shed. It’s just not aesthetically pleasing.
Second, if your plywood is already warped when you go to build something with it, you’re going to have a very difficult time. For instance, nailing or screwing a warped piece of plywood to 2×4 framing is more or less impossible. If you do get it securely attached, you are likely going to have some gaps and cracks around the perimeter.
Next, if you use warped plywood for anything structural in nature, it’s not going to be very structurally sound. Warped plywood is generally weakened, which means that it cannot bear nearly as much weight as it should. This is obviously not ideal for building purposes, and can even be dangerous too.
The other thing to take note of here is that warped plywood is generally warped due to exposure to moisture. If plywood has been exposed to too much moisture, not only will it warp, but it will also start to degrade and crumble. This in itself is of course also bad, because degraded and crumbling plywood is not structurally sound, and it can’t handle moisture well anymore either.
Are Some Types of Plywood More Prone to Warping Than Others?
The fact of the matter here is that many types of plywood are fairly prone to warping, especially with prolonged exposure to moisture. Therefore, it makes more sense to discuss the types of plywood that are less prone to warping, as opposed to those that are more prone to warping.
Now, one of the best types of plywood to resist warping is marine-grade plywood. This type of plywood is made with very high-quality veneers, as well as special waterproof glue. As the name of marine plywood implies, it is designed for use around or even in water. Seeing as water is a big cause of plywood warping, using waterproof plywood is therefore ideal.
If we aren’t talking about marine-grade plywood, then the number one type of plywood that can resist warping the most is Douglas fir. In terms of water resistance, once Douglas fir plywood has been properly seasoned, it generally can’t absorb much moisture, and it will more or less stop shrinking and warping altogether. When all has been said and done, the types of plywood that are least likely to warp are those that are the most water-resistant.
4 Reasons Plywood Warps
So, you got some warped plywood on your hands, but why did it happen in the first place?
1. High Moisture Levels
One of the main things that cause plywood to warp is moisture. Plywood that is exposed to much moisture, whether to high humidity levels or to a rainstorm, will likely warp. The reason for this is because most types of plywoods aren’t very waterproof or water-resistant.
Exposure to moisture means that they will absorb water. This will then cause the fibers to expand in certain places, thus causing warping to occur. This is especially the case if only one side of the plywood is exposed to moisture. The side that is exposed will expand in comparison to the side that stays dry, thus causing a warp.
2. Exposure to Sunlight
Another thing that can cause plywood to warp is sunlight. Now, this technically has to do with the heat that the sunlight produces. If one side of your plywood is exposed to plenty of sunlight, and the other is not, the side that is exposed to the sun is going to dry out. If one side of the plywood dries out and the other does not, it will cause a warp to occur, because the dry side is going to shrink in comparison to the moister side.
3. Gravity
Another reason why plywood may warp is due to gravity. For instance, if you have plywood laying down, and supported on both sides, but not in the middle, the middle is going to hang through. Eventually, this warp will become permanent. This can also be the case if you lean plywood against a wall at an angle.
4. Physical Damage
The other cause of warped plywood is physical damage, such as a big impact. That said, if a big impact is in question, then your plywood is more likely to crack or split than it is to warp.
5 Tips to Prevent Plywood from Warping
Now that you know why your plywood is warped, let’s go over some important tips for preventing it from occurring in the first place.
1. Keep It Out of the Sun
To prevent the plywood from drying up on one side, and therefore warping, keeping it out of the sunlight is strongly recommended. This is especially the case if only one side is going to be exposed to the sun, but not the other side.
2. Keep It Dry
Seeing as moisture is one of the leading causes of plywood warping, keeping it as dry as can be is recommended. The less moisture your plywood is exposed to, the lower the chances of it warping
3. Don’t Store It Flat on Concrete Ground
Another thing that can help prevent plywood from warping is not keeping it flat on some kind of concrete surface. Cement or concrete blocks may hold on to moisture that will then transfer into the plywood.
4. Store It Properly
You also don’t want to have your plywood laying flat on the ground, especially on top of each other. You also don’t want to lean the plywood against a wall. The best thing to do is to layer plywood onto thick pieces of wooden blocks. Make sure that you support the plywood in the middle with those wooden blocks. This will help prevent the middle of the plywood from sagging, and it will also keep it from contacting the ground.
For more tips on this, read my articles about how to store plywood outside and in a garage.
5. Seal It
Seeing as moisture is a big problem here, sealing your plywood with a waterproof sealant will go a long way in preventing it from warping. Some kind of polyurethane sealant is generally what is recommended for this purpose.
Can You Fix Warped Plywood?
Indeed, it is possible to fix warped plywood, at least if the warp isn’t too bad. There are a variety of methods you can use to fix warped plywood. This generally involves balancing moisture content in the wood.
For a full guide on this, read my article about how to flatten plywood.
Summary
You should now know why plywood warps, how to prevent it from warping, and what the most warp-resistant types of plywood are. Remember folks, warped plywood is essentially useless.