Shelf Width

[Luckbox]

I am planning on building some bookshelves. The area I want to put it is about 45” wide. My question is just how wide can make the shelves before they will begin to sage under weight. I was thinking of making the shelves out of ¾” plywood with a solid wood banding on the front. I figured that would make for some strong yet good looking shelves. Should I make a center support or will that be strong enough to hold that large of a span.

[radhak]

You should find a somewhat scientific approach here : http://www.woodbin.com/calcs/sagulator.htm

[schloff]

If you use 1x2 banding, that'll increase your load capacity greatly. Maybe even one on the back, too.

That should hold fine for the 45" span.

[cabinetman]

IMO, 45" is a too long. A front and back front edge buildup would help, but I feel with some weight would still be inadequate. I would still go with a center support.
.

[eezlock]

shelf width

Are you going to make these shelves fixed or adjustable? If they are fixed,
be sure and dado them on the ends...adds a lot more support, also use glue and screws in those shelf ends it will help support more weight.
If you are going to make adjustable shelves, I would install a verticle support
from top to bottom of the shelves to install an additional shelf support bracket
onto...helps to prevent sagging in the middle under all the weight.

[schloff]

IMO, 45" is a too long. A front and back front edge buildup would help, but I feel with some weight would still be inadequate. I would still go with a center support.
.

I would think that if the front and back were supported with a band, it would be adequate. I am an overkill guy, probably always will be, and I braced my shelves that were 43". But that was just because I had the materials. And the time.

[phi1l]

Unless the book case is going to be really tall, I expect it would LOOK better with a vertical support in the middle, in front of the shelves. That would allow you to (even with adjustable shelves) add a hidden support to the middle front of the shelves. I prefer that to actually reinforcing the shelves, because if you add up the space taken up for reinforcing would take away space for an additional shelf (if you need it).

[cwsmith]

Definitely too long! This is especially true with plywood, as it is significantly more flexible (in my experience anyway) than solid boards.

I've spent the last several months building the bookcases in our new library, using 1 x 10 pine stock. I try to keep the shelf width under 30 inches but there is simply no cooperation from the room layout and at the north end of the library, the location of the doors and windows prooved to be a challenge. There I have a bookcase that is 36" and two on either side of the window that measure 38" in width. With that length shelf board, the sag is just less than 1/4" at the middle. Not terrifically noticeable, but I know it's there! Problem is that putting a divider in the middle, is less aesthetically pleasing and more noticeable than the sag.

Adding a front horizontal support or band will help of course, but at 45 inches and with plywood, I think you'd still have some noticeable sag if fully loaded, especially after time. Using a hardwood band would add some strength, of course; but I think I'd still consider a divider, especially if you are going to completely populate the shelf.

I hope this helps,

CWS

[Bill in Buena Park]

I also think 45in is too long, especially for book weight - unless you create some shelf with a torsion box design, and that may not be visually appealing. Splitting the 45 into two segments, as actually two separate carcases or one with a divider, will yield shorter, stronger shelves. But I'd still probably over-engineer and add the front & rear 1x2 support rails.

[herb fellows]

+1 on the too long vote. In the end it depends on the actual load of course, but generally speaking I wouldn't go beyond 3 ft max without a center support.

[JimD]

I working on some now. The space I am filling is a little over 68 inches wide. I will loose over 2 inches of this to 3 uprights leaving each shelf about 33 inches long (I need to work on that because 32 would be much more efficient). I still plan to put edging on both edges although the shelf itself will be melamine particle board - worse than plywood for sagging.

Jim

[Luckbox]

Ok so it seems like the overall vote is I need the extra support. Now one more quick question. Should I build two units and join them side by side and put them on a single base, or would it be just as good if I was to build one unit with a center support, or One unit and have a strip than runs down the middle just on the front that could have shelf pin holes drilled in it and just simply add an extra pin or two for the front on the shelf.

[JimD]

I am building one large unit partially to save an extra vertical piece. But I could still change this. The design I am using is from Woodsmith and has a face frame. I've built two portable bookshelves built on this design and I like it. The vertical pieces of the face frame are only 2 inches wide. So if I double up the middle by building two units, the overhang would be only 1/4 inch on each side which I think would look funny. Or I could double the face frame too but I think that would look funnier. I think the single vertical will be strong enough but I am a little worried about the weight of the completed bookshelf. I may assemble it right in front of where it goes so I can just tip it up into position. I have a 27 year old son who is bigger than I am to help.

If you want to be able to move this yourself in the future, you may want to build two units. If you are willing to always have help when moving it, I would make it as one piece. It will take less material and I think it will look better.

Jim