Can they be saved?

[steve-norrell]

I recently finished built-in a bookcase/cabinet for a room that is destined to become an in-home office. All went well and they look pretty good after all the patching, filling, sanding, and painting -- especially if you don't look too closely.

However, a problem appeared after we began to fill up the bookcases. In the attached pictures the sagging of the top shelf on the left side is clearly visible (close-up picture) and I am looking for a way to remedy the problem without having to make completely new shelves.

The body of the bookcases and cabinets are 3/4 inch ply but the shelves are 1/2 inch birch ply (from HD) with "L-shaped" stiffeners across the front of each shelf. Shelves on left are 28 inches; 26 on the right. The shelves are 11 inches deep, including the stiffeners.

My plan is to add stiffeners, probably of oak, to the rear of each shelf after a) reducing the depth of each shelf appropriately, and, b) routing out the paint layers (<< 1/16 inch) on one surface at the rear of the shelf so there would be good glue adherance along the rear edge and the upper surface of the shelf.

My head is hung in shame for not using 3/4 inch stock. I know better for next time. But enough self-flaggelation . . .

Any advice on whether or not this will work?

Thanks, and regards, Steve.

[drumpriest]

In the future, you can check out this site, which will help you to determine your needs for shelves.

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

I personally have a thing against saggy shelves, so I overbuild mine. Typically I put a 1.5" to 2" front stiffener of some hardwood, and nothing on the back, but use 3/4 ply for the shelves. Never had one sag, and I've put some frightening weight on them. I've no idea if your idea will work or not, to be honest.

According to the sagulator, you'd be fine with the stiffener, depending upon how wide/thick it is.... what were you thinking?

[steve-norrell]

According to the sagulator, you'd be fine with the stiffener, depending upon how wide/thick it is.... what were you thinking?

Thinking? Huh? But thanks for the tip about the sagulator.

According to the sagulator the shelves, even with a 100 pound load should only sag 0.2 inches -- this seems to be quite a bit more than that. AND there is a stiffener on the front; and the books surely don't weigh 100 lbs. Could it be the plywood?

Regards, Steve

[RodKirby]

I had this problem with store-bought shelves that LOML wanted to stack her Quilting magazines (HEAVY!) VERY easy solution...

Empty the top shelf.

Starting at the bottom - insert a vertical brace in the center of the shelf(same depth as the shelf, same material as the shelf), so it is just a press fit - touches the shelf above. Continue with braces to the top.

Load up the top shelf - everything stays put - no sag

------------ Shelf
| brace
------------ Shelf
| brace
------------ Bottom

[Hellrazor]

Rod beat me to the punch. That was going to be my suggestion too.

[LCHIEN]

I think when you put the brace along the back, the front edge of the shelf will still sag appreciably.

Are those shelves on shelf pins? Are the removable? If so, not too late to put thicker shelves in.

[steve-norrell]

Starting at the bottom - insert a vertical brace in the center of the shelf(same depth as the shelf, same material as the shelf), so it is just a press fit - touches the shelf above. Continue with braces to the top.

Thanks to Rod and Hellrazor: As is almost always the case. the easiest solution may well be the best solution and it may be the one that we use eventually. The problem is that the LOML likes the wide-open spaces (she's a westerner) between the shelves.

And also to Loren: The shelves are on pins and can be replaced. And, there are stiffeners across the front already and, while you can't really see it in the photo, the sagging is much more pronounced toward the rear of the shelf. . .

. . . So being an old retired guy and a slouch by nature, I was hoping that adding a stiffener to the back would provide just enough rigidity to prevent the visible sag. Save lots of sanding, priming, and painting.

Besides, in a former life I was in a profession that encouraged experimentation and, who knows, I may be able to invent a reason to buy another tool. Anyway, I'll try some things and report back.

Thanks for the suggestions, regards, Steve.

[drumpriest]

The human eye will pick up a sag as small as about 0.04" Sure it could be the ply, and the ply might not be straight under any load, but you are asking a lot of 1/2" with the number of books on there. They weigh more than you think, try to pick them all up at once. ;-)

Anyway, you could certainly reduce the sag with a stiffener, and it may well be "enough". Why not try doing 1 shelf and see how it goes? You won't have wasted much material. If it doesn't work, then you are in for making new shelves.

[cwsmith]

From my experience, it's the plywood. Plywood makes for lousey shelves, it's just too flexible. Chip board and MDF are even worse. The latter will sag with a span as little as 22 inches.

Remedy would be to add braces at both the front and back edges of each shelf. Seeing that you have painted shelves, I'd recommend going with pine or poplar. Obviously the pine would be the most inexpensive way to go.

I built several self-standing bookcases a few years ago, using the economy grade pine from Home Depot. Those shelves were 10-inches deep and 24 inches wide and the overall height was 73 inches with a total of six shelves each. These were strickly economy-class bookcases using simple butted assembly, screws, and open backs. They were primed and painted to contrast with the room.

I used 2 x 4 crossbraces at the top, bottom, and middle of the back and fastened the sides to the top, bottom, and middle shelves using screws and hiding the holes with dowel plugs. Certainly an amaturish job at the time, but all I had to use was a circular saw and a drill w/guide. All the other shelves are adjustable using pins.

These bookcases are loaded, and there is NO sag or wobble after four years of use.

I hope this helps,

CWS

[cabinetman]

I'm willing to bet the stiffeners will not work. I go along with the swapping out to 3/4" plywood for the shelves. Not all plywood has the same flexural rigidity. I would use either maple, or birch, in that order, if you are painting.
.

[Tequila]

What's the back made of? I fixed up a saggy set of shelves on an old bookcase by drilling holes for shelf pins in the back. It takes a little work to make sure the holes line up with the sides, but it's a pretty easy fix and it basically cuts the deflection to 1/4 of whatever it is now.

[RodKirby]

If my solution doesn't work...

I will donate, and pay to ship, my entire Workshop to the US

[steve-norrell]

If my solution doesn't work...

I will donate, and pay to ship, my entire Workshop to the US

WOW! For that I will make sure it doesn't work and provide an address to which your workshop can be shipped.

Only problem would be building the house add-on to house it.

Regards, Steve

[gwyneth]

WOW! For that I will make sure it doesn't work and provide an address to which your workshop can be shipped.

Whoa, he didn't say where in the U.S., or to whom.

[steve-norrell]

I'm willing to bet the stiffeners will not work. I go along with the swapping out to 3/4" plywood for the shelves. Not all plywood has the same flexural rigidity. I would use either maple, or birch, in that order, if you are painting.
.

Are you trying to make a grown man cry?

You may well (probably are) right and the best solution would be either new shelves or the braces as suggested by Rod. I could also stack fewer books on the shelves, at least until I get around to making ones that are 3/4 inch thick.

This is turning into an interesting experiment . . .

Thanks for all the help. Regards, Steve