Should I put a permanent shelf in the middle of a bookcase?

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Hello
I am making a few bookcases for the local school. They will be made out of 3/4 (18mm) birch ply with a 1/4" plywood back in a dado and 3/4 x 2" poplar frame on the front. Two of them will be 2 feet wide by 5 feet high and the third will be 32" wide by 6 feet high.
My question is should I make the middle shelf in each permantely attached, dadoed to each side, so that the cases will not warp over time? If it matters I will use shelf pins for the shelves.
Thanks
Larry C
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If you are attaching a face frame and glueing in the back you should not have to worry about warp. You for sure want the back to be attached tightly whether with glue in the dado or screws if you use a rabbet instead of a dado.
I would definately attach at least a 3/4" wide strip of solid wood to the shelves fronts and backs if they are going to be make out of plywood.
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Larry C wrote:

You don't need to on those sizes, but if you like to over-engineer stuff, like me, go ahead and do it to "ease your pain." :-)
--

-MIKE-

"Playing is not something I do at night, it's my function in life"
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On the tall ones, I would. On the short one it's be a tossup.
Ed
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Larry C wrote:

any bookshelf's I have built the shelves are permanent. Just make them at different heights so accommodate different size books. The lower the shelves the higher
--
"You can lead them to LINUX
but you can't make them THINK"
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wrote:

The odds that the bookcases in a school will be abused is high. Someone will jam books onto a shelf which will tend to spread the sides. I'd consider it cheap insurance to throw in a middle fixed shelf. If you nail the back into that fixed middle shelf the bookcase will be much stronger and probably last twice as long.
R
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wrote:

The odds that the bookcases in a school will be abused is high. Someone will jam books onto a shelf which will tend to spread the sides. I'd consider it cheap insurance to throw in a middle fixed shelf. If you nail the back into that fixed middle shelf the bookcase will be much stronger and probably last twice as long.
R
Thanks for the input.
I think I will feel better with a middle shelf. It really should only take me an extra 10 minutes a case when I am routing the rabbits.
Larry C
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wrote:

Hey now! If you do that I'm calling the ASPCA! However, if you're routing the rabbets, I'll wish you good luck. ;)
Don't forget to have some little brass nameplates made up so people who will know did the nice work.
R
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stuff is designed to last a hundred years or so. Some folks call it overengineering or overbuilt. I prefer to think of it as strong.
<beating chest and letting out tarzan yell>
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Larry -
Good Man.
I have over 4000 books in the house so book shelves are not unknown.
36" wide is my no level - anything below is just fine.
32" wide shelves if supported on the sides are just fine. Supported - or on adjustable metal 'ladders' All of mine are adjustable, set once or twice in each house. We tend to set books in a case and not move them - but sometimes a collection grows out of a bounds and force change. Sometimes a rascal book binder / publisher produces a silly cm taller...
I'd go metal adjustments - routed out and placed within the wood - and the width and height is no issue. And fixing the center isn't needed.
Build a foot and it will be boxed in - strengthen the corners with real feet blocks. That will make a strong box. Some of my shelves have front stiles down each side - and across the top - picture frame the bare box but this causes an issue with books hiding behind.
Schools are more or less regulated in RH.
Martin
Larry C wrote:

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Larry C wrote:

It sure makes them stronger, I've seen overloaded bookcases warp to the point where the shelves start to drop off the pins. I'd rather build them with a fixed center shelf than have to go back and repair them in a year or two.
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Larry C wrote:

The above sentence is a complete design spec, if you think about it.
These book shelves will take a beating and are expected to "keep on ticking".
Once they buy them, the school board won't have money to maintain them.
Build them like a "brick out house".
60-70 years from now, some school superintendent will look at those book shelves and say "Thank you".
Lew
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Exactly. Not sure why people are pointing to bookcases they made for themselves as if that is an indication of the abuse a bookcase would take in a school environment. I don't suppose too many of the people here are four feet tall and make it a habit of climbing up on a bookshelf to get a book, or jamming in books, but these things certainly will happen in a school. Since the fixed shelf doesn't really have any impact on the usability of the bookcase and would take an extry ten minutes to do (if you stopped and had a beer in the middle), why _not_ do it?
R
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On Wed, 21 Oct 2009 07:06:07 -0700 (PDT), RicodJour

...boy, you guys are alot faster than me! I've always made my bookcases with a fixed center shelf...at least the longer ones. The time it takes to dado and install the shelf, true, isn't that much, but then you have to factor-in the extra piece in the faceframe and all that goes with it...as an aside, I usually finish the case before installing the back; it makes for better/easier spraying...shelves always get at least an 1 1/2" hardwood strongback/face.
cg
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On Tue, 20 Oct 2009 14:17:22 -0400, "Larry C"

I have two 7-foot bookcases, neither with a middle fixed shelf. After 15 years no signs of warping. It helps to seal/paint all sides. The back is what gives it strength from (sideways) racking forces. Use 3/4" for the shelves.
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wrote:

Exactly, the back and the face frame that he plans on using will keep the sides from bowing. The single dadoed shelf may not bow much if glued in place but what about all the other shelves? My 25 year old book case still stands proud however with out a back, it has a face froame on front and back.
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Leon wrote:

Not too long ago I repaired a big bookcase (over 6' square) on which the sides had bowed out due to the shelves being way overloaded with books. It had a back, but that didn't stop the shelves from falling right off their adjustable pins once the sides warped enough. I don't know how, but that's what happened--maybe the sides bowed out enough at the front, maybe the back floats, whatever. I fixed the center shelves in place and could see the sides return to their former position as I drove home the screws. Said bookcase now lives in our garage where the beautiful oak veneer looks a bit out of place, but it sure holds a buttload of woodworking stuff. I accept that with a back and face frame properly done it probably isn't necessary to fix the center shelf. But on the other hand unless there is a pressing need to have all the shelves adjustable a center shelf glued into a dado sure keeps those sides in place.
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wider than the widest case the OP mentioned.
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Leon wrote:

It's *somewhat* different, but I don't think it invalidates the idea that if you put enough weight on the shelves the sides are going to want to bow. The case I described has a vertical divider in the middle BTW, so in effect it is two 3' cases side by side, quite similar to what the OP mentioned. There are several ways to prevent the sides from going barrel-shaped and I have no philosophical attachment to any particular method, I'm just reporting what I saw....
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wrote:

It sounds like he's going to need some centre support, even if there is a back that is fully attached. Given the same situation, I'd go scope out some junk books, remove the cover spine and glue it to some similarly thick centre supports.
Never tried anything like that before, but it would be an interesting project to see how well one can hide centre supporting structures. They would have to be really dull subjects so no one tries to pull any out. I could just see it. Getting sued because someone pulled one of my bookshelves over on themselves. :)
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