Ideas to prevent sag on the front edge of book shelves.

[Glen Butler]

I am making some book shelves for a client and the simplest thing would be to edge band the front of the shelves and not worry about it, but books can get quite heavy and over time the shelves will sag. This is unnacceptable to me. The shelves are hickory mdf. I want to rabbet the shelves into a 1x2 of hickory. Is it a problem that that where the book shelves are taller than a man you could see the L shape on the underside of the shelf? I am also concerned that a plain 1x2 would look too simple, but I can't think of a way to dress it up.

[Kent A Bathurst]

Don't know if you have seen/used this:

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

I don't think the 1x2 front would look bad. Don't know if a simple way to dress it up - a beaded edge would look great, but you'd probably need to bead around the entire shelf opening. Sagging shelves would be the worst "look" possible.

[Mark Woodmark]

A piece of solid wood attached to the underside of the shelves on edge approximately 1/4" to 1/2" from the front edge of the shelf. The width of this apron board would be determined by the length of the shelf and what type books will be on it (heavy or not heavy). Then just edge band the front edge of the shelf. should have either the same at the back of the shelf or some sort of shelf support

[Rod Sheridan]

Hi, as others have indicated, a strip of solid wood will help greatly. I've included a photo of a strip I made recently for just that purpose....Rod.

[Jamie Buxton]

This suggestion is too late for your project, but for your next bookshelf, use plywood instead of MDF. Plywood sags less than an equal thickness of MDF.

[Chris Friesen]

...books can get quite heavy and over time the shelves will sag. This is unnacceptable to me. The shelves are hickory mdf. I want to rabbet the shelves into a 1x2 of hickory.

MDF isn't the best choice for heavy shelves. Plywood would be better, solid hickory better still.

In any case, your solution to put a 1x2 on edge is a good one and will stiffen it up. Also consider screwing through the back into the back edge of the shelf.

There's no need to rabbet the shelf into the 1x2, a butt joint will be fine. MDF has no grain, plywood has 1/2 the glue surface as long grain, and solid wood would be a pure long grain joint. Pretty much ideal circumstances for a butt joint.

[Scott Hildenbrand]

I did much like Rod did for the last run of shelves I made. They were short shelves so really I didn't need to worry about sag. Made them out of 1/2" ply and used a 3/4" face band, notched out like the photo above.

Next run I do will need to be 3/4" ply and 1" banding since it will be long span.

[Prashun Patel]

Two things will eliminate sag:

1) Place cleats along the rear edge. Either secure these to the wall, or to the underside of the shelves. If you don't want to make these visible, you can even drill shelf pin holes at the back and use shelf pins to provide 'invisible' support to the back.

2) 1x2 on the front edge. Your idea to rabbet the front and then to rest the shelf in the notch is good. You can roundover or chamfer the top and bottom edges of the front of the shelves. Don't get fancy; this will be plenty dressy and professional. More detailed moldings can be saved for the case.

I did this in a storage closet at home. A "short man" won't notice the band. From a distance, the 1x2's make the shelves look extremely thick and substantial.

[Robert Reece]

If you really need to beef up a shelf, you can somewhat hide a piece of angle iron behind that lip of the shelf. I made some shelves like that once - 2 1/4" lip with 1 1/2" piece of angle iron behind them. They span almost 6' and have text books on them (heavy!) and it doesn't sag at all.

[john bateman]

I have also cut a saw kerf in the bottom of a shelf, and embedded a 1/8" x 5/8" steel bar. They don't bend much.

[Paul Murphy]

I like the suggestion Rod posted, as it increases the glue area. I also like the looks, but I'm kind of a form follows function guy.

[keith micinski]

For lower shelves I like to put a piece of small crown molding underneath the front and the sides set back about a quarter of an inch. This looks nice and works well for stiffening up the shelves but on higher shelves like you said you would be able to see the under side of the shelf and I am not sure how that would look.

[Howard Acheson]

What is the width and depth of the shelf?

As already said, MDF have relativley little resistance to sag. It's not a good choice. 3/4" plywood is a better choice. It's lighter and the edge plies can be easily hidden with a solid wood facing strip which, if wider than the plywood, will add quite a bit to the resistance to sag.

You are correct that books are heavy. I generally use 30-35 pounds per running foot. But the best way to know is to take enough books to measure 24" and pile them on a bathroom scale. Divide by two to get an average weight and then use that amount to input into the "Sagulator". The Sagulator site (www.woodbin.com) has lots of good info about sag.

[Jerome Hanby]

I wonder if you could route a grove across the shelf bottom and hide a piece of all thread in it. You could tension it from the sides of the bookcase to add some sag proof support....

[Jerry Solomon]

Vertical pieces between the shelves starting from the bottom will prevent the shelves from sagging. This assumes that the bottom is fully supported. It's not the most elegant way but it does keep them straight.

[Dick Bringhurst]

If it's an adjustible shelf, I use hardwood for the visible edge and angle iron or aluminum on the back edge. Dick B.

[Scott Loven]

How about cutting a deep saw kerf underneath about 2 inches back from the front and glue a piece of steel in the slot. Should make it much stiffer and almost invisible. I also would do a dado on the back and sides.

[Scott Hildenbrand]

If you really need to beef up a shelf, you can somewhat hide a piece of angle iron behind that lip of the shelf. I made some shelves like that once - 2 1/4" lip with 1 1/2" piece of angle iron behind them. They span almost 6' and have text books on them (heavy!) and it doesn't sag at all.


Wow.. A 6' unsupported shelf span.. You crazy man.. You crazy... ;)

So.... Is this kind of what you did? This is the best thing that comes to mind when I think of doing such an overkill thing.

But then, with a 6' span, it needs to be overkill.. Wouldn't say to go through this with a standard bookshelf. :)

Anyway.. Glen.. You still hadn't said what WIDTH the shelves will be.. Or the depth.

[Glen Butler]

Sorry, been away from the puter for a while. Thanks for all the resonses. I especially like that load calculator. The MDF core veneer has already been purchased, it was difficult to find plywood core. The shelves are 12" deep, well I guess 11" actually. They are spanning 28.5". I like the idea of the angle iron or bar stock steel if I am still having problems after running a 1x2 along the front edge. But it sounds like the consensus is that a 1x2 will look fine and some simple roundover on the edge will look just fine.

[Greg Portland]

A 1x2 hickory edge will be extremely strong, assuming it is properly attached to the shelf. If you are only using glue then be sure to rough up the MDF edges. With my shelves I liked the look of the simple 1x2 and slightly more elaborate crown and base moulding. I used pocket screws + filler plugs for 1/2 the shelves and then used a domino for the rest (faster & better looking joint).

[Jeff Monson]

I've made a few display cases, and have used a 3/4x1 1/2" hardwood strip with a roman ogee routed in the face to "dress it up" glued to the front of the shelf, then I will take a strip of the same hardwood that is 1/2"x3/4" and glue it to the bottom of the shelf 1 1/2" from the front. It really dresses up the shelf and I have not had one bow yet.