When I did my workbench chest of drawers with OSB drawer boxes, someone asked me if OSB could be used for making more finished things, like furniture. I had used OSB for other things in the past, but thought I would do something to show what is possible with this very economical material. As usual, when I get an idea, I run right out and start doing it without fully thinking it through. As a result, this project would start and finish over the course of five months, since I didn’t want to do the very extensive sanding that was needed to finish the stool in my shop.
The idea was to get the stool from only one sheet of 5/8″ OSB. Here it is up on my table saw, ready to lay out the pattern:
The pattern was something that I quickly drew on SketchUp. A copy of it is at the bottom of this page.
The construction is layered from one side to the other, with individual slices stacked to make the whole unit. This is often referred to as trans-lam construction, and is well suited to this material, as it works with its strength.
After laying out the basic shape, I used a piece of 4″ PVC pipe to radius the corners:
Ready to cut out.
The jigsaw is the best tool for cutting parts like this from the full sheet:
I will need four of these full size pieces to make the ends of the stool.
Number two marked using the first as a template:
After all four were cut out, I sanded the first one smooth to use as a guide to trim the other three. I figured that it would save a ton of sanding to do this now.
Two full slices make up each end, but were too thin when put together, so I added a layer between using pieces cut from the rest of the sheet:
The pieces are carefully cut to fit together tightly, nailed and glued to the layer below. Due to its longer working time, I’m using polyurethane construction adhesive to put this together.
Next I added the other full size slice, glued and clamped, and left to dry overnight:
And did the same for the other end. These two form the structure of the stool, and all that is needed next is to stack layers between to fill out the width.
The next day, I could trim the centre layer using a pattern bit in the router:
I now have the two ends finished and fairly smooth.
To make the stool more comfortable to sit on, I decided that the seat and backrest should be contoured in. Knowing that doing that with a sander would take hours, I go a head start on it by stepping the layers progressively narrower, as shown here in a drawn mock-up.
The back support and seat layers, ready to assemble:
The stretchers are just 3″ x 3″ blocks of OSB glued and screwed together:
This looks easy, but I had to make sure that the blocks were well aligned and that they were going up perpendicular to the side.
The back rest and seat added in the same way, with glue and screws:
The whole thing was clamped and left to dry for five months.
Actually, the clamps came off the next day, but the stool sat untouched until it was warm enough outdoors to do the final sanding.
First step in the process was to round over the edges with the router:
Then the sanding could begin:
Starting with the belt sander with an 80 grit belt, I go over the entire chair.
Even with the layers stepping down, I still had to do a ton of sanding on the backrest and seat:
After the belt sander, I switched to the random orbit sander with 100 grit disks.
Very dusty work, I’m glad I didn’t do this indoors:
Some final hand sanding to get the areas where the machines couldn’t reach.
With the sanding done, I applied a coat of linseed oil:
The finished stool:
It’s heavy, solid and very comfortable to sit on. It was also cheap for the material, with the total cost somewhere around $30 – $14 for OSB and the rest for other materials (glue, nails, screws, etc.). Of course, there is the time it took to build, but I think the results were worth the effort.
To do it again, I would make it less bulky – thinner legs, thinner seat.
I made a video showing the build from unloading the sheet from the truck, to applying the final oil finish months later: