Shelf Strength

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Forum topic by Tig1242 posted 06-29-2012 12:46 PM 4597 views 0 times favorited 10 replies Add to Favorites Watch
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14 posts in 3346 days

06-29-2012 12:46 PM

I am looking at building a bookshelf 3’ wide. I am concerned about shelf sag, so what would be the strongest wood, ply wood, MDF or something else?

Do I need to put in a center support column so the shelves would be only 1.5” on each side?


10 replies so far

View Charlie's profile


1101 posts in 3370 days

#1 posted 06-29-2012 01:01 PM

The Sagulator is your friend!

I used 3/4 inch, 11-ply birch plywood for the wide shelves in our kitchen cabinets. They all got “faced” with 3/4×3/4 maple. That facing was more for looks as I don’t have edge banding, but the hard maple will add even more sag resistance. The 3/4 plywood by itself has real good numbers though.

View tenontim's profile


2131 posts in 4828 days

#2 posted 06-29-2012 01:02 PM

For 3’ shelves, 3/4” lumber or plywood will be strong enough, especially a hardwood like oak, maple, ash, etc. If your bookcase is going to have a back, you can cut a dado into the back or put screws through it, into the shelves to give extra support to the shelves,

View Tig1242's profile


14 posts in 3346 days

#3 posted 06-29-2012 01:14 PM

Thanks Guys!

View 404 - Not Found's profile

404 - Not Found

2544 posts in 4053 days

#4 posted 06-29-2012 10:19 PM

Tenontim is right, attach the shelves to the back with screws to eliminate any chance of sagging

View Charlie's profile


1101 posts in 3370 days

#5 posted 06-29-2012 11:05 PM

I have adjustable shelves. Kinda hard to screw them in from the back when the cabinet is screwed to the wall. :)
Sagulator is an awesome tool… hehehe

View AndyDuframe's profile


48 posts in 4674 days

#6 posted 06-30-2012 04:34 AM

I’ve always liked the method of attaching a hardwood band or apron across the front of the bookshelf. This makes it almost impossible for the shelf to sag. Plus, this is just about the only way to add support to an adjustable shelf.


View MonteCristo's profile


2099 posts in 3272 days

#7 posted 06-30-2012 04:58 AM

Personally I would put a center support on a 3ft span. Maybe stiffening the back side of the shelf as described will do but why risk it, especially if the shelf will store a bunch of hardback coffee table type books that are really heavy.

-- Dwight - "Free legal advice available - contact Dewey, Cheetam & Howe""

View Lee Barker's profile

Lee Barker

2172 posts in 3934 days

#8 posted 06-30-2012 05:16 PM

I agree that 36” is a mighty long span.

You could edge your shelves with 3/4×1 1/2 or 1 1/4 stock, front and back, and they’d be great, but you’re adding some look of mass there that would have to blend right with the carcase.



-- " his brain, which is as dry as the remainder biscuit after a voyage, he hath strange places cramm'd with observation, the which he vents in mangled forms." --Shakespeare, "As You Like It"

View Jamie Speirs's profile

Jamie Speirs

4168 posts in 3940 days

#9 posted 06-30-2012 05:26 PM

Just put a lip on it

So it looks like a capital L

Larger the lip the larger the span that

is possible


-- Who is the happiest of men? He who values the merits of others, and in their pleasure takes joy, even as though 'twere his own. --Johann Wolfgang von Goethe

View Charlie's profile


1101 posts in 3370 days

#10 posted 06-30-2012 05:58 PM

3/4 inch shelf faced with 5/8×1-1/4 walnut. This is for a 33 inch shelf that will hold a microwave on one shelf and cookbooks on the top shelf…

I haven’t put a finish on this piece yet. It does add some mass, but this hutch will sit on top of an inch and a quarter walnut counter top so it should look fine. :)

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