Carpentry and Woodworking - Bookcase Question

I'd like to build a book case that's about 4' wide by about 7' tall by about 9" deep, made out of solid (read, no plywood) clear red oak. I'll be using a dado to secure the shelves to the sides of the bookcase (read, non-adjustable). The bookcase will have no back and will be open.

Given that's each shelf is 4' wide, how strong, over-time, will the shelves be? I'm concerned about sagging especially with the weight of books. Will 4' be ok, or should I shorten these down to a smaller width?

If at all possible, I'd like to stay away from putting a back on this, although, I guess I could tack some 1/4" oak-plywood on the back and on each shelf.

Thanks guys!

Ry.

http://www.woodbin.com/calcs/sagulator.htm

Here is a site to help with the strength of span question. In my expeience 36" is the most unbraced for books.

Attaching a back will go a long way to prevent racking and will help with the strength of the shelves.

Ry,
As soon as you get it completed, somehow an oversize book will emerge.
Why not run your dados vertical and install some recessed adjustable shelf brackets, (rockler.com). This way you can always turn your bowed shelves over too..... or replace them.
fred

rvitek,

Is the reason for not installing a back because it will be visible from both sides? As chfite says, a back will help the situation a great deal. If a back is definitely out, I believe 48 inches is stretching a little beyond what you could expect to remain straight over time with the weight of the books on them.

If you have enough vertical space for all the shelves with a little space leftover, or if you use fewalt's suggestion for adjustable shelves, you could add a 3/4 thick by 1" to 1.5" wide strip (rail) to the front and back of each shelf. Keep the top of these rails even with the top of the shelves. I would put them on the front even if you decide to add a back to the case. Glue and nail, or even better, use biscuits to join the rails to the shelves. This will add the extra strength needed to keep the shelf straight.

Good luck

Most plywood shops or moulding shops will sell red oak planks in varying widths and thicknesses,
3/4", 7/8", 1", 1 1/8". I built a wall to wall, floor to ceiling bookcase for a doctor, who, specifically requested solid shelves that would hold heavy medical books.And I had a span of 5'.
There was a skin rear panel but I didnt want to attempt to use it for support. I also didnt dado the shelves but used brass pegs. I drilled a series of holes for adjustment. Anyway..I ended up cutting shelves out of solid oak that was 9/8"
thick or 1 1/8" by 12" by 5' long.I selected this thickness after a serious eyeballing, and it worked out excellent, no sag, and heavy books, side by each , all in a row ! Nice clean shelf too but it weren't cheap ! Hope this helps.
Good luck
ryk

4' is too far, even 3', using 3/4 material is going to sag without some type of support. The only thing you can do is either use thicker material (which may still sag), or apply some T shaped material to the underside of the shelves, preferably steel, but aluminum should work too.

Of course, this depends on what kind of books are on it. If it's just paperbacks, no big deal.


Plus, with no back, you're going to need some type of corner bracing to keep the whole thing from collapsing unless one side is being bolted to the wall. Bookshelves should _always_ be secured to a wall in some fashion!

rykurd, how long after you built the shelves did you check for sag?
I bet they have sagged by now..

Hate to add fuel to the fire but 48" is way to wide with no back support. The shelves will sag. But since your shelves are permanent, why not add a 1" x 1" support brace at the back and under each shelf that runs the length of the board and is secured to the sides. You won't see it and it should help significantly. I did that in a laundry room with a span of approximately 50" and it worked well.