Plywood: the good, the bad and the ugly
I’m wrapping up a storage unit project for a client this week.
It’s a series of panels that fit together with some dividers, tops, bottoms, fixed shelves and adjustable shelves to form a large amount of space in their newly renovated finished basement. I used 3/4″ thick maple plywood for most of the parts, with solid making up the majority of the trim and maple-veneered particleboard for the large doors and drawer fronts.
I machined a series of dadoes across the panels to accept mating workpieces. I set them all at 3/16″ deep, which left 1/2″ of material left over, as the plywood I’m using is only 11/16″ thick.
Why plywood?
For a project like this, solid wood is obviously not an option. It would have been incredibly expensive and not provided any real benefit. Particleboard was an option, but plywood is much lighter and is less likely to have problems if it comes into contact with water. Because of the dadoes that are machined into the faces of the panels, plywood is much less likely to split than particleboard. There was one spot where I had to machine dadoes into both faces of the workpiece, at the exact same distance from the edge, which would have made a particleboard panel very weak. I certainly weakened the plywood panel, but with a bit of care it’s been fine. The centre one-third or so of a piece of particleboard is less dense than the outer one-third, which makes machining dadoes into both faces at the same distance from the end very risky.
Take the good with the bad
Even though the plywood pieces are much easier to handle due to their lighter weight, and are stronger in general, there are some downsides to using it. The face and back veneers are very thin. This isn’t necessarily the same with all plywood, but the brand I’ve been using is borderline problematic. I have to be very careful when machining and sanding it. I also have to ease any edges that aren’t going to receive iron-on edge tape, otherwise they’ll be much more likely to chip. This isn’t the end of the world, though.
While plywood is fairly stable dimensionally, it’s very prone to warping. Some of these panels have cupped to the point of being visually noticeable. Right now, I’m at the stage where the main panels are in, but most of the fixed shelves and all of the adjustable shelves are not. In some cases, there is a 3/4″ difference in the opening between the bottom (where the vertical panels are fixed to the bottom) and the middle of an 80″ long panel. Thankfully, I can usually force things back to even, though it’s not always easy.
It also throws off measuring for doors and drawers. It’s not easy to make each drawer in a six-drawer bank 1/16″ wider than the previous one. And I’m sure lining up all the drawer fronts and doors is going to be a challenge, once the time comes.
All in all, plywood is a good material. But like anything, it has its pros and cons. I’m familiar with how each material reacts, but I was a bit surprised about how the sheets I picked up last week have been reacting. I might consider taking a look at other types of plywood the next time I need some for a project. Likely the price will rise, but if the job is right, a more expensive board might give me a more predictable result.
Want to learn more about the different types of sheet goods? Read my “Sheet Good Essentials” article.
Pros and Cons
Particleboard (top) is stable, though it’s heavy and can be weaker, depending on how it’s used. Plywood is great for many reasons, though it tends to warp and twist, especially if it’s used in large panels.
Rob is a studio furniture maker and the editor at Canadian Woodworking & Home Improvement. Instagram at @RobBrownTeaches
Plywood is so unpredictable. I bought a few sheets of shop grade birch at Windsor Plywood, that has 9 layers, thinking that should be relatively stable. After cutting, it had a sharp bend in two of the panels. I recently bought a shop grade sheet of birch with 7 layers at PJ White Hardwoods and it was relatively flat with a shallow graceful bow. Interestingly, the Windsor store is heated but the PJ White warehouse is unheated (I live in North Vancouver). And if I were to redo the purchase a few months down the road, the conditions might be reversed! Sometimes, I feel it is luck of the draw.