The Power of Plywood All Around the House

Of course you've heard of it, but you might not know all the uses and benefits of this workhorse building material

Kenny Grono April 27, 2013

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Before we start talking about plywood, it helps to know what plywood replaced. Though wood has been with us forever, modern plywood has existed for less than 200 years, and its omnipresence is quite recent. Now we deck the roof, sheath the walls and build cabinets with plywood. It wasn't long ago, however, that all of these tasks were performed by joining individual boards side by side into a larger piece of wood, or by simply nailing them next to one another. Though the nostalgia for salvaged wood has renewed interest in these boards and techniques, there are many benefits to using plywood instead.

Janet Paik

Ashley Meissner

Types of Plywood

There are many different types of plywood, but this ideabook focuses on the types at your local home center, and that you might use for DIY projects around the house.

Plywood is used for just about everything today. For example, in this photo there is probably plywood under the hardwood floor (probably a tongue and groove subfloor plywood), and most likely plywood under the exterior wall siding. The furniture piece pictured is made of solid wood boards, attached side by side where the boards are smaller. However, most cabinets these days would be made from smooth hardwood plywood.

Buckminster Green LLC

Grading

When you think of plywood, you probably think of a sheet of CDX. CDX plywood has a "C" side, a "D" side and an "X" side. "X" means the glue can be exposed to the elements for a while before it falls apart. Plywood is made by gluing many thin layers of wood (veneers) together. The wood grain of each layer runs perpendicular to the previous, which reduces the wood's tendency to split.

There are four different grades of plywood: A, B,C and D. Remembering the difference between the grades is easy — it's just like school. If it has earned an A grade, it's free from imperfections. A D grade doesn't mean it's useless — it's fine to face into the house or cover with shingles.

Plywood can work for all types of jobs, and the grade makes a big difference. CDX plywood is good for rough construction, but you wouldn't want to build a cabinet with it. A nice piece of birch plywood with an A-grade face would work fine to sheath your shed, but it's expensive, and you'd be paying for quality you don't need, since the sheet will be covered with siding.

Buckminster Green LLC

Structural Benefits

You can see three different sheet goods used in the construction of these new houses in Philadelphia. The yellow sheets are exterior gypsum, used to create a fire-resistant barrier between houses. The bays' faces are sheathed in oriented strand board, or OSB (more on that later). CDX plywood is everywhere except on the faces of the bays. Go back a hundred years and the facade of this building might have been sheathed in 1-by-8 boards, or whatever width the lumberyard had that day.

Here's a thought experiment: Take four pieces of lumber and nail them into a square. Now push on the square from one side. Will it stay square? No, it will shift into a rhombus. Now cover this square with individual boards. Will this keep the square square? It's not much of an improvement. If you nail the boards diagonally this helps, but it's nothing like putting a single sheet of wood over the whole square — it wouldn't budge. This, in a nutshell, explains the structural advantage of being able to use a single piece of plywood.

Buckminster Green LLC

If you've ever driven a screw into a board without predrilling a hole first, you know that inserting a wedge into wood causes it to split along the grain. All plywood resists this, since the wood grain of each layer is different than the last.

But what if, instead of gluing together large sheets of wood at right angles, you glued together small pieces of wood at all different angles? You'd get a similar effect while making use of small wood pieces that would otherwise become waste. The result of this process is OSB plywood, or oriented strand board. OSB is less expensive than CDX, and under the right conditions performs well.

Buckminster Green LLC

I've seen CDX plywood and OSB get rained on when delays happen and roofs and siding aren't installed. The CDX buckles in places but generally holds up. The OSB turns to mush much faster. Once the glues begin to break down, you're left with little pieces of wood.

The product shown here is the Zip System from Huber; it has a weather-resistant barrier applied to OSB. Green is for the walls; brown is for the roof. This saves you the step of stapling up a barrier like Tyvek after installing the plywood. Once the seams are taped, you have a continuous air barrier. Compare that to the old boards nailed up with tons of gaps for air to blow through, and you can see how today's building techniques can save you energy.

Buckminster Green LLC

Sustainability

In recent years attention has turned to the glues in plywood, and what fumes the product is off-gassing into our homes when used inside. To reduce harmful VOCs, look for plywood with glues that have no added urea-formaldehyde.

The plywood used in the construction of the cabinets in this picture goes one step further. The doors, shelves and cabinet boxes are all made from bamboo plywood. Bamboo is a grass that grows quickly, and it is a sustainable substitute for wood from trees. Sustainability is all in the details, though, so do your homework to make sure the life-cycle costs of the product are indeed less than the product you are replacing.

There are also plywoods made from sorghum and wheat. The look of these alternative plywood products is part of their appeal.

Nic Darling

Uses

Plywood is too useful to end up only cladding buildings and getting covered up by other building materials. It has many uses inside, too. Here, plywood is used to create a unique railing for the stairs. When you take into account the labor saved by using large, strong, straight sheets of wood in building products, plywood is an economical solution to many problems. You are limited only by your imagination.

Tip: Make sure to use the right thickness. Plywood that's 3/4 inch is very rigid and good for walking on, shelving etc. If you are applying a layer of plywood over another surface and you just want a smooth surface — say a luan plywood underlayment for flooring — 1/4 inch will do the trick.

Sylvia Elizondo Interior Design

OK, so now you're heading to the store to buy plywood for your next project. Here are some tips:

If it's for under your floor or roof, it should be tongue and groove plywood, where the boards mate together like puzzle pieces for stability at the seams. I told you to buy 3/4 inch, but you may show up to the lumber yard and see 23/32 inch. Bring a tape measure or calculator and get the closest to the size you need. Contractors talk about 1/4 inch, 1/2 inch and 3/4 inch, but you'll also see 7/16 inch, 15/32 inch and all sorts of other fractions.
If you are building something like garage shelving that doesn't need to be perfect, but should be relatively free of imperfections, get a 3/4-inch B or C plywood.
If you are planning to build cabinets or an interior project where the surface of the plywood will be seen, I recommend using a hardwood plywood, like a birch plywood that has a smooth A-grade face. Hardwood plywood can be stained as well as painted, and either will result in a nice finished product.

There are many beautiful woods that can be applied as the surface veneer to a plywood made primarily from less expensive woods. Let your imagination go wild and make a statement with plywood. The Mesopotamians first created plywood by gluing wood together when there wasn't enough around. In modern times we don't need to waste wood either, and plywood brings with it enough other benefits to make it a win-win scenario.

Next: See what you can do with drywall