I am planning on building built-in bookshelves that would span the length of a wall. Each unit would consist of a cabinet base ~2' across with a set of bookshelves mounted on top. The depth of the cabinets would be ~2' and the depth of each bookshelf would be ~12".

The plan is to construct the cabinet and bookshelf carcasses out of 3/4" plywood, then add hardwood face frames to each unit. 1/4" (or 3/8") rabbets would be cut for each shelf. Also, the cabinet and bookshelf would have plywood backings mounted, probably 1/2". Everything would then be mounted to the wall and each other.

Is the strength of the plywood enough to hold up the weight of the bookshelves + books without bowing? I would like to avoid it, but should I go with additional upright 2x4s between each unit for added support?

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  • If I understand your description correctly, the width of each bookshelf is 2' and they are supported by dividing walls in the base cabinet directly below. This should be plenty string enough. However the table in the center section may sag a bit without some sort of apron support at least at the rear. Check out the 'sagulator' on the net to determine what spans you can use there.
    – Ashlar
    Commented Jun 16, 2020 at 23:02
  • The material used for the cabinets are quite adequate for the selves. As Ashlar commented on, the only issue would be the center desktop in your drawing. What is the length of the connecting piece between the cabinets? Commented Jun 17, 2020 at 1:36
  • "Is the strength of the plywood enough to hold up the weight of the bookshelves + books without bowing?" as I visualise the way this would be, the plywood wouldn't be holding up the bookshelves. Instead it would be holding them tight to the wall (i.e. pulling inwards). Since so much of the weight is transferred down through the whole assemblage to rest on the floor I can't imagine it wouldn't be fine, unless your plywood sheathing is particularly dreadful quality (which, regrettably, some plywood is today). Any concerns however go away completely if you go into your studs, or a solid wall.
    – Graphus
    Commented Jun 17, 2020 at 15:59
  • The cabinets are 2' wide (four total cabinets in the design). The desktop spans 5', supported by a separate set of plywood uprights. An apron spans its width (~5' x 6" x 3/4"). The apron is offset from the back by 2 1/4" (trying to maximize leg room). Commented Jun 17, 2020 at 18:15
  • The material you selected and the design is way more than adequate to support any books placed on the desk. Plus with the apron spans on the desktop and only 5' length. the desk top is well supported. Good luck on your build. Commented Jun 18, 2020 at 21:48

1 Answer 1


I just put 3/4" plywood down as the floor for my new shed. Granted, it's on 16" OC joists, not a 24" span, but I expect the shelving that will be going in there to be significantly heavier than any 2 foot shelf of books could be and I'm not worried about the strength of the plywood.

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