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I am looking for recommendations to choose between a diverse spectrum of 3/4" thick plywood-y materials, such as MDF board (or similar) as well as stratified but sanded plywood. In this particular example, my dimensions are around 14"x60" but I have other application with similar area size but different dimensions.

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I was originally planning to go with joining 2 1x8 sideways using biscuits and than stain it but I'm thinking plywood may be more durable to warping over time, especially because I don't plan to affix the upper shelves so they can be removed.

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    Are you planing on having a center support, even just at the back? Asking any 3/4" material to hold books and not bend is a tall order over 60" – JPhi1618 Sep 27 at 17:28
  • It has it already, can't see in the picture – amphibient Sep 27 at 17:35
  • Back support the whole width of the shelf – amphibient Sep 27 at 17:36
  • Back support will lead to front-only sag, which is worse (from a content stability standpoint). – isherwood Sep 27 at 17:47
  • Put less weight – amphibient Sep 27 at 17:51
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Here are some of my experiences:

3/4" boards

The max commonly available width is going to be 12" (11.25" actual), so for 14" you would have to join two 8" boards ripped to width. This requires more work than the other options and you have to find two very straight boards to start with. They can warp in the future, but glueing and biscuiting two pieces together helps with that. It will be strong and light, but I don't think it's worth the effort unless you're really trying to match materials with something else.

Plywood

Will be straighter than boards, but it's not immune to warping. Comes wide enough to use one piece and is pretty easy to cut. The cut edge is not acceptable to leave visible. It may sag in the front over that 60" span. Even with a back support thats asking a lot (but wait, there is a solution).

MDF

Perfectly straight and will never warp. Very easy to cut, although it does create a lot of dust. Same issues as plywood - will sag in front and the cut edge can't be painted easily. MDF must be painted and will be quickly and irreversibly damaged by water if the surface is not sealed (with paint).

Recommendations

Plywood and MDF are the frontrunners. If you want to stain, use plywood. If you are going to paint. MDF is a good choice. Since neither of them have usable edges, I would glue/biscuit a 1x2 board onto the front edge. This gives the shelf a visible thickness, covers the bad edge and adds some strength to prevent sagging. I still wouldn't trust it to hold heavy items without a center support, but the edge board will at least help it hold its own weight without sagging (and some light items).

  • I agree with your main points, but none of these will span 5 feet well. – isherwood Sep 27 at 17:50
  • I think the edge board will give them a fighting chance. 3/4" cabinet grade ply and MDF are pretty stout. 5' is on the limits of my comfort - I'll agree with that. – JPhi1618 Sep 27 at 17:53
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60" is too long of a span for 3/4" material even with nothing on the shelves. If they don't sag noticeably immediately from their own weight, they soon will.

I would install corbels reaching at least 2/3 depth at the center point for each shelf. Then you can use whatever you like, as almost any 3/4" material will span 30" fairly well.

If you really want a free-span shelf, 1-1/8" oak stair treads are what I'd use, and nothing less. They're commonly available in 72" lengths, and you can use either the bullnose front or the square back facing forward. I'd expect around 1/4" sag with a full load of small and medium-sized books.

  • Corbels are a good option and can be found to match your style. – JPhi1618 Sep 27 at 17:55
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I would use plywood, it is much stronger than MDF. Finish the edge with heat activated veneer, or moulding.

What are you putting on the shelves? If you are putting heavy items such as books, 60 inches is too far of a span. I have a 30 inch span that doesn't sag noticeably with books. You could probably go a little more, maybe 40 inches without additional support in the middle.

  • I'm putting anything that won't sag it – amphibient Sep 27 at 17:39
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Birch ply has a price comparable with AC pine ply at the same thickness, but is stiffer. It also will take penetrating wood finishes more evenly without conditioners or partial sealers. It's difficult to find in stock in 4*8 sheets, but most stores should be able to special order it.

However I'm not sure I'd trust it at that span, either, not for books or anything heavy.

I recommend a 3/4" divider in the center, to prevent shelf sagging. I know 20" would be better if using pine or another softwood species. Corbels would also be okay.

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