It’s been a long time since plywood was considered “flat.” In fact, most modern plywood is made with a curved veneer that gives it more strength and stability. I got frustrated with ending up with half a sheet of plywood I couldn’t use so I went in search of answers to see Is plywood flat anymore?
You can still find flat plywood at some lumberyards and home improvement stores, but it’s not as common as it once was. Your best bet is to order it from a specialty woodworking store or online retailer. Since most plywood is now made with a curved veneer, it’s important to take this into account when choosing plywood for your project.
Read on as I’ll discuss what this means for your woodworking projects and how to choose the right plywood for the job.
How to Straighten Warped Plywood?
You can use the sun to straighten warped plywood. Set the warped sheet on a level surface and pour some hot water on the warped area. Now place the plywood on a surface with direct sunlight, the humped side up. Place a heavy object on the plywood to keep it from curling up.
Leave it in the sun and check it after every 10-20 minutes. I have found that in some cases the heat will make the wood fibers expand and straighten out the plywood.
The following video is helpful for cupped plywood.
Video showing how to flatten plywood
Use Heavy Weights
You can use heavy weights to flatten warped plywood. Place the warped sheet on a level surface and put some heavy weights on the edges. You can use dumbbells, kettlebells, or any other type of weight. Leave the plywood overnight so that the wood fibers have time to expand and straighten out.
Be sure to place the weights evenly across the curved plywood so that it doesn’t warp in the opposite direction.
Use Clamps
This is another effective way to straighten out warped plywood. Place the sheet on a level surface and clamp it down at the edges. Use as many clamps as you need to keep the plywood from moving. Leave the plywood overnight so that the wood fibers have time to expand and straighten out.
It helps to clamp it down on the specific places it is warped, rather than clamping down the entire sheet.
This is the method I used when my plywood got wet on a trip home.
Use Steam
You can use steam to straighten out warped plywood. Place the plywood on a level surface and pour some boiling water over the warped area. Put a heavy weight on top of the plywood to keep it from curling up. Leave the plywood overnight so that the wood fibers have time to expand and straighten out.
You can also use a steam iron to straighten out warped plywood. Hold the steam iron close to the warped area and let the steam loosen up the wood fibers. Be sure not to touch the plywood with the iron as this could cause damage. After a few minutes, the plywood should be straight.
I have bought plywood that is flat and after a day or 2 at home, it warped. Be sure to stand your plywood on edge to enable air circulation.
Use Wet Rags
I have also seen people use wet rags to straighten out warped plywood. Simply place the sheet on a level surface and put wet rags on the warped area. The water will loosen up the wood fibers and allow the plywood to lay flat.
Be sure to use enough wet rags to cover the entire warped area. You may need to replace the rags a few times as they dry out.
These are some of the most effective ways to straighten out warped plywood. If your plywood is severely warped, use multiple methods to straighten it out. Be patient and let the plywood dry completely before using it for your project.
Hot Tips on How to Find Flat Plywood Sheets?
Flat plywood sheets are generally found at specialty board supplier companies although there are still plenty of flat sheets at places like Home Depot and other big-box stores. To find flat plywood, you want to visually inspect all sheets by running your eye along all edges to check for straightness.
Look for any inconsistencies in the thickness. Inspect the sheets and check for any damages. Check for overlapping core veneers and voids in the plywood. Also, make sure that the edges are squared off and not beveled.
Video showing how to flatten warped plywood
Here are some of the best tips on how to find the best plywood sheets:
Check the Packaging
One of the easiest ways to tell if a sheet of plywood is flat is by checking the packaging. If the packaging is warped or bent, then chances are the plywood inside is also warped. Avoid buying any plywood that has damaged packaging.
Inspect the Sheet
Once you’ve found a sheet of plywood that you think is flat, inspect it closely. Run your hand along the surface to feel for any bumps or waves. If the plywood is warped, it will be very difficult to sand or plane down later.
Look for Knots
Another way to tell if a sheet of plywood is flat is by looking for knots. If the sheet has a lot of knots, it’s likely that the wood fibers are not aligned. This can cause the plywood to warp over time.
Avoid Sheets with Crooked Edges
Another way to tell if a sheet of plywood is flat is by looking at the edges. If the edges are crooked or not evenly cut, then chances are the plywood is warped. Avoid buying any plywood that has crooked edges.
Be sure to carefully inspect the edges of the plywood before you buy it. Check the thickness and consistency of the edges and make sure they’re all the same.
Bring a Friend
It helps to have a second set of eyes when you’re trying to find flat plywood sheets. Bring a friend or family member with you to the store and have them help you inspect the sheets.
They’ll be able to spot any warping or damage that you might miss. Plus, they can help you carry the plywood sheets to your car.
Do Not Have Your Plywood Delivered
One of the most common mistakes people make is having their plywood delivered. Delivery drivers will just throw the first sheet off the pile and won’t care what it’s like.
If possible, pick up your plywood sheets from the store yourself. This way, you can inspect them before they’re loaded into your car.
Buy from a Reputable Lumberyard
I often tell people to buy their plywood from a reputable lumberyard. Lumberyards typically have higher-quality plywood than your local hardware store. Plus, the employees at lumberyards are usually more knowledgeable about woodworking and can help you find the best sheets of plywood for your project.
Call Ahead
If you’re planning on buying plywood from a lumberyard, call ahead and ask if they have any flat sheets in stock. Many times, lumberyards will special-order flat sheets of plywood for their customers.
This can take a few days, but it’s worth the wait if you need perfectly flat plywood for your project.
Inspect Multiple Sheets
Do not just grab the top plywood sheet from the stack and assume it’s flat. Inspect multiple sheets of plywood before you make your final decision.
Plywood is often stored outdoors, so it can become warped from the elements. By inspecting multiple sheets, you’re more likely to find one that’s perfectly flat.
Take Your Time
Do not be in a hurry when you’re trying to find flat plywood sheets. This is an important decision and you need to take your time.
Carefully inspect each sheet of plywood and compare them side-by-side. This will help you find the best sheets for your project.
Is A-Grade Plywood Susceptible To Warping?
Not all A-grade plywood is susceptible to warping, but it can happen if the wood fibers are not aligned. A-grade plywood with a lot of knots is more likely to warp over time. Be sure to check for crooked edges and overlapping core veneers before you buy the plywood.
I must also mention that there are various factors that will make even the best A-grade plywood susceptible to warping. These include, but are not limited to:
The type of wood used
In my experience, I have found that hardwoods are more likely to warp than softwoods. This is because hardwoods have a higher density, which makes them less stable.
The thickness of the plywood
Thicker sheets of plywood are more likely to warp than thinner sheets. This is because there are more wood fibers that can become misaligned.
How the plywood is stored
How and where you store your plywood can also affect its flatness. If you store your plywood in a humid environment, it is more likely to warp. This is because the wood fibers will absorb moisture from the air and swell.
You should also avoid storing your plywood in direct sunlight, as this can cause the wood to dry out and become brittle.
The adhesive used
Some adhesives are more likely to cause the plywood to warp than others. For example, urea-formaldehyde (UF) adhesives are known for causing warping in plywood. This is because the UF molecules expand and contract with changes in temperature and humidity. As a result, the wood fibers can become misaligned and cause the plywood to warp.
To avoid this, look for plywood that is made with phenol-formaldehyde (PF) or melamine-formaldehyde (MF) adhesives. These adhesives are more stable and less likely to cause warping.
Changes in humidity and temperature
The changes in humidity and temperature can cause the wood fibers to expand and contract. As a result, the plywood can become warped.
To avoid this, store your plywood in a stable environment with consistent temperature and humidity levels.
Is Baltic Birch Plywood Flat?
Baltic birch plywood is a type of plywood that is made with birch veneers. It is known for being strong and durable. Baltic birch plywood is also less likely to warp than other types of plywood. However, the 1/4″ and 1/8″ Baltic birch is more likely to warp than the thicker sheets.
To avoid warping, store your Baltic birch plywood in a stable environment with consistent temperature and humidity levels. You should also avoid storing it in direct sunlight or in a humid environment.
Video on how to straighten warped or bowed plywood
What Kind Of Plywood Stays Flat?
Double Fir plywood is among the flattest plywood you can find. This type of plywood is made with two layers of fir veneers. The veneers are glued together with a cross-grain construction, making the plywood less likely to warp. To ensure that your Double Fir plywood stays flat, store it in a stable environment with consistent temperature and humidity levels.
You can buy Double Fir plywood here at Lowes.
Other types of plywood that are less likely to warp include:
Douglas Fir Plywood
Exterior glue-bonded Douglas Fir Plywood is among the strongest and most durable types of plywood. It is also less likely to warp than other types of plywood.
Particleboard Core Plywood
Particleboard core plywood is made with a particleboard core that is sandwiched between two layers of veneer. The particleboard core makes the plywood less likely to warp.
Marine Plywood
Pressure-treated marine plywood is designed to resist warping in humid or wet conditions. It is made with waterproof adhesives and is ideal for use in boats or other watercraft.
ApplePly and Baltic Birch
ApplePly and Baltic Birch are two types of plywood that are less likely to warp. Both types of plywood are made with multiple layers of wood veneers. The veneers are glued together with cross-grain construction, which makes the plywood more stable and less likely to warp.
Tips on How to Prevent Warped Plywood Shelves
To prevent your plywood shelves from warping, you need to store the plywood in a stable environment with consistent temperature and humidity levels. Poor storage is among the most common causes of warped plywood shelves. You should also avoid storing the plywood in direct sunlight or in a humid environment.
If you live in an area with high humidity levels, consider using a dehumidifier to keep the air dry. Here are some more tips on how to prevent your plywood shelves from warping:
Avoid using adhesives that are known for causing warping
Some adhesives, like urea-formaldehyde (UF), can cause the wood fibers to expand and contract. As a result, the plywood can become warped. To avoid this, use adhesives that are more stable, like phenol-formaldehyde (PF) or melamine-formaldehyde (MF).
Store the plywood in a cool, dry place
High temperatures and humidity levels can cause the plywood to warp. To avoid this, store the plywood in a cool, dry place. If possible, store the plywood in an air-conditioned room or in a temperature-controlled storage unit.
Use bracing to support the shelves
If you are worried about your plywood shelves warping, you can use bracing to support the shelves. Bracing will help to distribute the weight evenly and prevent the shelves from sagging or becoming warped.
Do not overload the shelves
If you overload the shelves, it can cause them to sag or become warped. To avoid this, do not store more than 50 pounds on each shelf.
Use supports to prevent sagging
If you are worried about your shelves sagging, you can use supports to help distribute the weight evenly and prevent the shelves from becoming warped.
Is MDF Flatter Than Plywood?
In my experience, I have found that MDF is indeed flatter than plywood. The main reason for this is because of the manufacturing process. MDF is made by breaking down hardwood or softwood into very small wood fibers and then combining those with wax and resin binders under extreme heat and pressure.
This creates an extremely strong, flat sheet that does not have the same risk of warping as plywood does.
Another advantage that MDF has over plywood is that it is much denser, meaning it is less likely to dent or chip on the surface. It is also less likely to absorb moisture, making it a good choice for applications where plywood would typically warp or swell, such as in humid bathrooms or kitchens.
While MDF is generally flatter than plywood, there are certain types of plywood that are less likely to warp than other types of plywood. For example, marine plywood is designed to resist warping in humid or wet conditions. ApplePly and Baltic Birch are also two types of plywood that are less likely to warp.
Does Plywood Flatten Over Time?
When properly stored, plywood can last for many years without warping. However, if the plywood is not stored properly, it can warp over time. Warped plywood is more likely to occur if the plywood is stored in a humid or wet environment, or if it is exposed to direct sunlight.
Be sure to properly store your plywood in flat layers in a cool, dry place to prevent warping.
To do this I recommend standing your plywood on its edge in a rack to ensure air can circulate around the entire sheet.
Final Thoughts – Is Plywood Flat?
Woodworking will inevitably require you to use plywood at some point. It is important to be aware of the different types of plywood and their potential for warping. By following the tips above, you can help prevent your plywood from becoming warped.
Hopefully, this article has helped you understand a bit more about plywood and how to prevent it from warping. Happy woodworking.
