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Plywood Shelf Support - Cover Exposed Edge of Plywood

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Forum topic by avxflyer posted 802 days ago 2693 views 0 times favorited 13 replies Add to Favorites Watch
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avxflyer

3 posts in 802 days


802 days ago

Topic tags/keywords: plywood sag sag support face board

Hi Guys,
I’m installing some shelves into an entertainment niche in my house. It’s an opening about 8 feet high and 4 feet wide. I’m using 3/4×1-1/2 birch to support the shelf on 3 sides. The actual shelf is 3/4” birch plywood. I want to hide the exposed edge of the plywood and the cleats so want to attach a piece of 3/4×3 birch to the exposed edge of the plywood and also want this to support the weight of the shelf since the span is 47”. What is the best way to attach the board to the edge of the plywood? I was thinking of using dowels, but maybe just Gorilla Glue is sufficient. Any tips? I don’t want to have screws or nail holes along the exposed wood.


13 replies so far

View devann's profile

devann

1735 posts in 1317 days


#1 posted 802 days ago

I like using biscuts for applications like that. Instead of a biscut you could also use a spline.

-- Darrell, making more sawdust than I know what to do with

View felkadelic's profile

felkadelic

193 posts in 1164 days


#2 posted 802 days ago

Biscuits are probably what I’d use, but you could also use pocket screws depending on how visible they’d be (I’m having a hard time envisioning your project in my head)

View Lifesaver2000's profile

Lifesaver2000

512 posts in 1737 days


#3 posted 802 days ago

If I understand correctly, the solid wood board will be at a right angle to the plywood, flush at the top and then projecting down a couple inches below the ply to hide the cleats.

In similar situations I have created a 1/4 inch by 3/4 rabbit in the solid wood then glued the ply into the rabbit. Since you want this edge band to help support the shelf, this method makes sure the weight on the shelf is transferred directly to your edging strip. No mechanical fasteners needed.

This is probably a little more work than the biscuits or pocket holes, but if you don’t have a biscuit cutter or pocket hole jig it will do the job.

View jusfine's profile

jusfine

2280 posts in 1550 days


#4 posted 802 days ago

Lifesaver’s plan is what I would do also, it will provide more glue surface and support.

Those are large shelves, make sure your cleats on the wall are nailed or fastened securely to the studs to prevent them from crashing down.

-- Randy "You are judged as much by the questions you ask as the answers you give..."

View JJohnston's profile

JJohnston

1577 posts in 1916 days


#5 posted 802 days ago

I think this is what Lifesaver is saying, and I’d go this way. Not only are mechanical fasteners not needed, they wouldn’t do any good anyway – mechanical fasteners don’t transfer shear across a joint, and that’s what you’ve got here. Just make sure they’re glued good, and use something that doesn’t creep, like plastic resin glue instead of yellow.

-- "Sorry I'm late. Somebody tampered with my brakes." "You should have been early, then."

View Loren's profile

Loren

7387 posts in 2272 days


#6 posted 802 days ago

You can just glue it but make sure you aren’t gluing a distortion
into the shelf when you do.

An argument could be made for actually gluing a center bow into
the plywood to counteract weight on the shelf. Even with
the overbuilding you are doing, I’d be cautious about expecting
the shelf to support books without bowing a bit in the center –
hence the theory about gluing a counter-distortion into it.

If using sold wood for the front you can mill a bit of a rabbet
into the front board (solid wood part) and use the rabbet for
alignment. If you have a biscuit joiner that is easy too. I
wouldn’t bother with dowels. They aren’t worth the
trouble for this job.

-- http://lawoodworking.com

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waho6o9

4821 posts in 1201 days


#7 posted 802 days ago

+1 for Lifesaver’s plan as well, maybe front and back if you can do it.

If the shelves are 24 inches deep you might want to consider a center support also. Post pictures when and if you have time. Sounds like a fun project.

All The Best.

View Lifesaver2000's profile

Lifesaver2000

512 posts in 1737 days


#8 posted 802 days ago

The drawing above by JJohnston is exactly what I was trying to describe. I will also mention that this is a good time to check the Sagulator to make sure that amount of edging is enough. I checked it using the default loads, and it seems to just barely come in under the maximum on sag. Without the edging though it would be much worse.

View Sawkerf's profile

Sawkerf

1730 posts in 1693 days


#9 posted 802 days ago

Another agreement with Lifesaver and JJohnston. Just make sure that your solid wood is ever-so-slightly proud of the ply shelf surface. If it’s too low, you might get a sand-thru. If it’s too high, be careful saning it flush to avoid sand thru.

-- Adversity doesn't build character...................it reveals it.

View Lifesaver2000's profile

Lifesaver2000

512 posts in 1737 days


#10 posted 802 days ago

Well, just re-read the OP, and he said the shelf will be supported by cleats on three sides, so with this amount of edging on the front sag should not a be a problem.

View Lifesaver2000's profile

Lifesaver2000

512 posts in 1737 days


#11 posted 802 days ago

What has worked well for me on making the shelf and edging flush is to use a flush trim bit on the router table with a high fence that has a gap on the bottom for the edging. Since the plywood is 23/32, if you make the rabbet 3/4 “deep” then that gives you 1/32 to trim off with the router bit. Done right it makes for a perfectly smooth transition.

View avxflyer's profile

avxflyer

3 posts in 802 days


#12 posted 802 days ago

Thanks for all the tips! My initial plan was to use dowels. I bought a jig and went to use it this morning and found it sucked! The included bits were bent ever so slightly and I knew the project would suffer from it. By the time I ran into this issue, I already had the cleats installed and they extend the full depth of the shelf, the same as the plywood. If I go with the method above in the pictures, which seems to be the best, I’d have to remove all the cleats and trim off the depth of the cut in the edging so that the edging could extend the whole width of the shelf, or I’d have to make an additional notch out on either end of the support. I’ll chalk up that mistake to education for next time. The other problem for me on this solution is, I don’t have a router table or a steady hand! I’m going with the biscuit idea and add another tool to the toolbox. THANK YOU ALL!

View gfadvm's profile

gfadvm

10714 posts in 1314 days


#13 posted 801 days ago

You can cut that rabbit on the tablesaw quickly and easily if you choose to.

-- " I'll try to be nicer, if you'll try to be smarter" gfadvm

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