How to pick the right plywood thickness
Choosing the right plywood thickness depends on the type of project. When applying plywood as a decorative covering, a thickness of 1/4″(6mm) down to a single veneer may suffice. When using plywood to create structure in furniture, or building construction a thickness of 1/2″(12mm) to 1″(24mm)+ may be required depending on the strength needed.
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Plywood thickness matters. A difference of a few of millimeters can mean your project lacks the required strength and structure, or could be entirely too heavy and overbuilt. Below we go into further detail to help you find the right plywood thickness for your project.
What is “plywood thickness”
Plywood thickness is the distance from the top to the bottom of a plywood sheet, and is drastically small in comparison to plywood’s length and width. Thickness is one of the key factors to determine the structural integrity, load-bearing capacity, flexibility, and suitability for various applications of plywood. Different projects will require specific thicknesses to ensure that the material can deliver the desired performance.
What happens if I get Plywood Thickness wrong
Plywood that is too thin can cause bending and sagging, which compromises the overall safety of your project. However, if your plywood is too thick, you may discover that the project is overbuilt, heavy, and less malleable.
What Plywood thickness should I use for…
See below the various projects which require different thicknesses of plywood. Lightweight furniture projects are where you want your plywood to be thinner, while heavier furniture and structural projects will require thicker plywood. Below are the answers for a few different projects.
Shelving
3/4“ thickness is an industry-standard. If you’re making a shelf for heavy items then you will want to go for at least this thickness. This will ensure that your shelf can bear the weight of your items and not fall.
How to avoid Sagging Selves
When making a shelf that will support a lot of weight or will be over 4′(120cm) long adding a Small 2″(5cm) strip of plywood below the front edge of the shelf will add more resistance to sagging, than increasing the thickness of the plywood.
Tables
Anything between 1/2“ and 1“ – it will depend on the desired outcome of the project. Should the table be more portable or more rigid. Tables come in all shapes and sizes and so the choice comes down to whether you are making a dining, coffee, or bedside table, and the exact dimensions you want it to have.
Bed frames
For sturdiness and ultimate comfort while sleeping – start with a 3/4“ thickness as a minimum. Any thinner than this and you may experience sagging which would negatively impact your bedtime experience. For anyone who is on the heavier side, aim for thicker plywood such as 29/32“.
Interior wall panelling
5/8″ is the best all-around thickness for this. When it comes to the interior walls of your building, you need a thickness which can maintain some level of soundproofing while still allowing the building to have some ambient sounds.
Load-bearing walls, roofs, and floors
Structural plywood is ideal for building strong and sturdy buildings. The thickness can range between 3/8″ and 1 3/16“. The thicker the plywood is, the more durable the building will be if there is an earthquake or exceptionally strong wind.
Sheds
The all-around best choice is 3/4“ CDX plywood. At an absolute minimum, go for 5/8“ thickness, but keep in mind that if you live in an area that experiences harsh weather or winters, the thicker the better.
Boats
Anything between 1/4“ to 3/4“ is used when building boats, and your choice here will vary depending on the size and style of boat that you’re aiming to build. For smaller boats such as a skiff or canoe, you will want anything up to 3/8“ to maintain speed and agility. Sailboats will require at least 1/2“ for stability.
Special Considerations for Plywood Thickness
Precise cuts and intricate shapes
Thinner plywood allows you to achieve precise cuts, curves, and intricate shapes. Techniques like bent lamination, where thin layers are glued together to create curved forms, can be achieved with thinner plywood. Thicker plywood allows more freedom to do edge treatments, such as bevels, chamfers, or rounded edges.
Outdoors and wet environments
If your project is outdoors or in a wet environment, you will need to ensure you are using “exterior-grade” plywood. Thicker sheets of plywood have more veneer layers which make them more resistant to moisture. Boats and other sea-based projects should make use of “marine-grade” plywood – which uses waterproof glue.
Does the style of joint matter?
When using thicker plywood, you are given more material for creating strong joints. Dado joints, dovetails, mortise and tenon joints are easier to use when the plywood is thicker. For more details on joints – check out our post here.
Nominal vs Actual thickness
Nominal thickness is the measurement given in the description of the plywood when you purchase it. However, be aware that the actual thickness can vary by around 1/32“. This is due to the process of sanding which is performed on plywood sheets – which causes irregular measurements to appear.
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The bottom line is that the exact thickness of plywood you want to use will depend on your exact needs and design specifications. This guide has given you a starting point so you can make adjustments to suit your project.