Can I use biscuits to join BC plywood?

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Forum topic by opalko posted 04-01-2015 12:00 AM 1233 views 0 times favorited 8 replies Add to Favorites Watch
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135 posts in 2457 days

04-01-2015 12:00 AM

Topic tags/keywords: plywood biscuits

I am making a set of recycling bin shelves for my garage out of 2×4’s and 19/32” BC plywood. The frame is the 2×4 material and the shelves that the bins sit on are the plywood. Doing this in a hurry and I screwed up and made the shelves too narrow…..aaarrrrghhh! Actually what happened was I made them wide and had plenty of room but when I set it in the garage it took up too much space, so I thought.. “I’ll just knock 6” off and it will be fine.” wasn’t.

My question is: since I still have the cutoffs from the original way I built it, can I join the cut-offs to the too-short shelf with biscuits? I’ve only used biscuits with real wood, and perhaps good quality plywood. You know what home center BC sanded ply is like. The kicker here is that the shelves (will be 20”x24” with the added in 6”) will have to support the weight of a full a big thing of newspapers etc. Or am I stuck buying another sheet of plywood to start over? To get an idea of what I’m making, look at this photo:

Garage shelves that are sort of like what I'm building...picture these only wide enough for just one bin stacked 4 high

8 replies so far

View CueballRosendaul's profile


484 posts in 1561 days

#1 posted 04-01-2015 12:13 AM

Use a long tenon instead. Cut a 1/4” slot in the edges of the shelf and the pieces you cut off. Make the slot about 1/2” deep, then cut a tenon out of hardwood just a tad under 1” to fit in the slot. I think you’ll be sorry with biscuits in a butt joint on plywood.

You can make the slots with two passes through the saw blade, just flip the piece around on the second pass so you’re sure the slot will be in the middle of the edge. Make the slots first and cut the tenons to fit the slot. Once you get one right, the rest of them will go fast.

Another option is to add a face frame piece as a cleat to the bottom of each front edge to give it some support, in which case you may be able to use the biscuit joiner. Beware that biscuits swell up and could blow some bulges in the surface of the plywood.

-- Matt CueBall Rosendaul. I don't think I've ever had a cup of coffee that didn't have cat hair or sawdust in it.

View Mike Throckmorton's profile

Mike Throckmorton

124 posts in 1086 days

#2 posted 04-01-2015 12:19 AM

I’ve done it when cobbling scrap ply together to make a mockup.

If I had to do it again, I’d do it with splines. Less effort to be accurate, arguably stronger.

Edit: yeah, what Matt said.

-- You are never complete, you just draw a line where done is and stop at that line.

View cutmantom's profile


388 posts in 2456 days

#3 posted 04-01-2015 12:33 AM

It will work, might not have the maximum strength though, could add some pocket screws

View rwe2156's profile


2119 posts in 902 days

#4 posted 04-01-2015 12:52 AM

Not gonna work, dude. Your edge joining plywood which is about the weakest joint there is and not only that, its got to be weight bearing.

You can use the cutoffs but will have to scab on a wide piece of plywood or 1X material underneath to span the joint.

Like Cueball said, you could go with 1×2’s on edge front and back but you don’t need biscuits just glue and screw them. This is probably the best solution.

Or, you could use full width 1X4’s laid flat front and back edge screw plywood from the top.

-- Everything is a prototype thats why its one of a kind!!

View opalko's profile


135 posts in 2457 days

#5 posted 04-01-2015 01:02 AM

I can’t change the thickness of the ply by adding anything underneath or on the front edge as the 2×4 part is already built for an exact fit between the ply shelves.

View exelectrician's profile


2327 posts in 1849 days

#6 posted 04-01-2015 01:02 AM

...or you could join the 6” strip back on with biscuits and then have the join at the back where the stress is low …..

-- Love thy neighbour as thyself

View opalko's profile


135 posts in 2457 days

#7 posted 04-01-2015 01:13 AM

I won’t have enough material with the added 6” to rotate the shelf to make the join at the back.

View opalko's profile


135 posts in 2457 days

#8 posted 04-01-2015 01:13 AM

Thanks for all the replies so far!

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