plywood shelf supports question

15 years ago

I am getting my hand in doing a little bit of cabinetry:

I am making 34W"x28" deep shelves with 3/4" plywood above my refrigerator and I was wondering if I need to install steel strip support across the plywood to stop it from sagging.

Also I would like some advice on how to join the plywood shelves to the vertical pieces, which are 3/4" thick veneered MDF (no choice here, they are fridge cover panels for the kitchen cabinets) I was thinking to install cleat on each side from the bottom to hold the shelf and also use some L brackets from above. But 3/4" screw will be the longest screw that can be used.

The box formed will be a shelf/cabinet but will be covered by doors.

Thanks in advance

Comments (6)

furnone
15 years ago
I suggest you fasten a 1 1/2" stiffener on the front and back edges of the plywood. That should be adequate to prevent sagging unless you are storing excessively heavy loads on the shelves. It will cover the exposed plywood edge as well as hide somewhat the cleats that support the shelves. Screws that go 3/4" into the MDF will be adequate. I would space the screws about 6" apart. Drill and countersink the holes in the cleats slightly larger than the screws and be sure not to overtighten the screws or they will strip out.
PoorOwner
Original Author
15 years ago
Hi, do you 1 1/2" high or wide? What kind of material should the stiffener be made of?
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furnone
15 years ago
3/4" x 1 1/2" applied flat to the edge of the plywood. It will stick down 3/4" below the edge of the plywood.

I would use the same wood as the cabinets, maple, oak etc. or even poplar.

Here's a handy web site that has an illustration and will compute the sag factor:

Here is a link that might be useful: Sagulator
aidan_m
15 years ago
Consider using Baltic birch (Russian Birch) 3/4" Multi-ply. It will not sag. You don't need to add thickness on the front or back- the 3/4" panel is plenty rigid. The finished edge actually looks cool since it is all solid hardwood veneers. Or you can cover the edge with solid wood, but there is no need to increase the 3/4" thickness- so you get more storage space.

For the side supports, I would use the KV standards and nail them to the sides of your existing panels. They are strong enough for bookshelves. Installation is easy for a retrofit like you are doing. The shelves will be adjustable.

Here is a link that might be useful: KV shelving standards
PoorOwner
Original Author
15 years ago
Hi Aidan, where can I get this plywood you are talking about? I have seen Birch at Lowes but not sure if it is te same thing you are referring to?
aidan_m
15 years ago
It is only available at specialty lumberyards that deal primarily with cabinetmakers and woodworkers. Some places on the internet will ship it to you directly, peices cut to size. (have them cut it oversize a little bit in case the edges get banged up in shipping)

The close up of the piece depicted in the link is of 1/2"

Here is a link that might be useful: Baltic Birch Ply