Build a Bench from Scrap Wood


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Oct 24, 2023

Build a Bench from Scrap Wood

Gear-obsessed editors choose every product we review. We may earn commission if you buy from a link. Why Trust Us? DIY wood project uses leftover pressure-treated lumber to create some extra seating.

Gear-obsessed editors choose every product we review. We may earn commission if you buy from a link. Why Trust Us?

DIY wood project uses leftover pressure-treated lumber to create some extra seating.

Lumber prices are so high today that I can’t imagine throwing out leftover wood. It’s like throwing money right into the trash can. But what do you do with it? I asked myself that question when I finished building a set of stairs this summer. The finished portion of the stairs consisted of five stringers, a set of risers and treads, a set of handrails, four posts, and a run of baluster with 2 x 4 supports. That was nearly $700 worth of lumber.

The unused portion of those stairs (scrap wood) filled two heaping wheelbarrows. It was the stuff that I cut out so that I could build the stairs out of the premium material, most of which was in the center of the board. Building something from scrap is a challenge because it reverses the normal order. In most cases, you build using the best part of the materials, not the discards. But I like a challenge, so I vowed that I would find useful stuff to make out of the remnant lumber. And in the process of looking at that pile of scrap, I started talking to people here, colleague Brad Ford and long-time contributor Joe Truini, a former carpenter and cabinetmaker. We decided to launch a series on simple projects for beginners devoted to building projects out of scrap wood. Consider this little bench as the first in the installment.

What follows is an overview of that process, and some of the tools and materials that we used along the way.

But here’s the process in a nutshell. All it took were six cuts on a miter saw and a handful of screws to produce this sturdy little bench. And it is sturdy; it weighs exactly 42 pounds. Sit on it, or put some flower pots on it. It’s good either way.

Out of the two wheelbarrow loads of wood, four pieces caught my attention. But what do you do with a 37-inch-long piece of pressure-treated 2 x 12? I had the same reaction with two short pieces that were 20 inches long and another piece that was about 32 inches.I stared at those four pieces of wood for about ten minutes before it occurred to me that there was a small bench hiding in them. I laid the wood down on a flat place on the garage floor. The long piece became the seat, the short pieces the legs, and the medium length piece was the support. Let’s say you don’t have four pieces of wood that are the same dimensions that I show here, the process remains the same. Lay them out on a flat surface and position them to get a sense of what you can make out of them.

As we state above, the process took only six cuts, all of them made with a Harbor Freight 12-inch miter saw. If you don’t have a large miter saw like this, an ordinary circular saw will be just fine. You probably won’t get the furniture-grade cuts that we achieved, but you’ll still end up with a nice, sturdy bench.

We began with the legs. Using the layout process described above, we tipped the legs to what we judged to be an angle that looked attractive and would provide a fair amount of stability. We marked a line on the edge of the wood, set the blade on a sliding T bevel to that line, and then set the bevel on the saw to match the blade on the T bevel. According to the bevel angle on the saw, this was exactly 24 degrees.

We cut bevels on the top and bottom of one leg, then used that leg to mark and cut the second leg. We then compared the two legs and found that they were nearly identical.

Next, we laid the cut legs on the support. We tipped the legs so that the bevel angle on the top of the legs aligned with the top edge of the support. We used a sharp pencil to trace the leg angles on the support. To double-check our work, we held the sliding T bevel on the lines we just drew and saw a slight discrepancy between its blade and the line.

It was hard to say how that discrepancy arose, but it told us that we would probably have to tweak the saw's miter setting so the angles on the support and the legs would match.

We set the top edge of the support against the miter saw fence and then swung the saw’s arm until the blade aligned with a miter line we marked on the support. We locked the miter saw arm at that position and, sure enough, found the same slight discrepancy that we noted above: The miter angle was off by slightly less than one-half of one degree. It was more like 24.5 degrees than the 24 degrees shown on the saw’s bevel gauge. We locked the saw at 24.5 degrees and made one cut on the support.

This is important: Owing to this angular discrepancy (between lines marked on the wood that indicate the actual angle, and what the saw’s miter gauge reads), cut both miters with the saw arm fixed in one position. Don’t cut the right miter, then swing the saw arm to the left and cut the left miter. This is a recipe to produce two slightly different angles.Leave the saw fixed in one position, cut the miter, then swap the support end for end and cut the second miter.

From there, it’s a fairly simple matter to screw the parts together. First, our 2 x 12 stock was actually 11-1⁄4 inches wide (here "wide" means measuring directly across its face). So that the support would be centered on the legs' width, we marked a line 4-7⁄8 inches in from the edge of each leg. The math: 4-7⁄8 and 1-1⁄2 (the thickness of the support) and 4-7⁄8 equals 11 ¼ inches. On both legs, we also marked an X on the right side of this line. The X tells us which side of the line the support belongs on. Without the X marks, you could inadvertently screw the support and legs together with the support on opposite sides of the line (don’t laugh; I’ve done that).We clamped the support in a woodworking vise so its mitered edge was aligned with the bench top. We aligned the layout mark on the legs with the support and screwed the parts together. We took the subassembly of these two pieces and stood them upside down on the bench top (upside down allows the parts to stand on their own). We clamped them firmly to the benchtop, then screwed the second leg to the support. Finally, we stood this subassembly (two legs and the support) on the shop floor, and screwed the top to the legs. In all, we used eight screws: two screws through each leg into the support and four screws through the top (two into each leg). That may not sound like a lot of screws, but note that these are gigantic, deck-building screws (No. 10 and rated for use in pressure-treated wood).

First, do not drive the screws through the legs into the support with the body of the screw parallel to the support’s long axis. This is a recipe for weakness as screws driven parallel to the grain do not grip as firmly as screws driven at an angle to the wood’s grain. Drive the screws perpendicular to the face of the legs and into the support; this positions the screws at a fairly steep angle to the grain of the support (which is parallel to the support's long axis). Not only does this permit the screws to bite into more grain, it reduces the chance of such large screws splitting the support.

Next, when driving the screws through the seat into the legs, offset the position of each screw to account for the slope of the leg. If you don’t, and you center the screw on the leg (that is, centered where the leg meets the top), you will inadvertently drive the screw right out the side of the leg. Offset the screw position to account for this slope, toward the outside face of each leg. This will result in a driven screw fully buried in lumber.

You can leave the bench as is or sand and finish it. Since we were unsure of whether the bench will be used for a plant stand or for people to sit on, we smoothed the top. We used a random orbit sander and 60-grit and 80-grit sandpaper (you can sand the legs and support if you'd like). If you plan to use this as a planting bench to support flower pots, you can stop there. If you intend to sit on it, sand it with two more grits: 120 and 150. If this bench is to be used outdoors and not as seating in your shop, shed, or garage, any exterior wood stain or finish—other than paint—is suitable for it. Paint doesn't bond particularly well to pressure-treated wood. Use any finish on the bench that you would use on your deck. Any exterior wood finish from a clear preservative up to a semi-solid wood stain will work well. Apply it with a soft brush or roller suited to these finishes and surfaces. Let the finish dry, then take a seat.

Roy Berendsohn has worked for more than 25 years at Popular Mechanics, where he has written on carpentry, masonry, painting, plumbing, electrical, woodworking, blacksmithing, welding, lawn care, chainsaw use, and outdoor power equipment. When he’s not working on his own house, he volunteers with Sovereign Grace Church doing home repair for families in rural, suburban and urban locations throughout central and southern New Jersey.

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