I am trying to build a sideways bookshelf. The space I have to fit the bookshelf in is:

Depth: 13.7 inches
Length: 87.5 inches
Height: 35.5 inches

When I looked online for store-made bookshelves, none of them came close to matching these dimensions. So I'm thinking of making my own bookshelf. However, I've never made a bookshelf before, so I am looking for some pointers.

My basic thinking is that I just buy

  1. 2 pieces of 87.5'' x 12'' for the top and bottom of the bookshelf
  2. 2 pieces of 12'' x 33.5'' to support the top of the shelf
  3. 1 piece of 87.5'' x 35.5'' ask the back of the shelf


  1. In the above dimensions, I assume the boards supporting the top of the shelf are 33.5'' and not 35.5 because I am assuming that the top and bottom of the shelf are each 1'' thick. Is that a good assumption or should it be thicker/thinner?
  2. How should I make the shelves? I assume I can make 3 shelves in the space, each being ~10.5'' in height. (Explanation: 33.5 is the starting height inside the shelf, add two boards in the middle, each 1'' thick, and we get 31.5, divide each space up evenly = 31.5/3 = 10.5.) How would I support those shelves so they don't bend? Would making only two shelves be easier?


  1. Are there any tips/tricks/helpful hints about making bookshelves that a novice like me might overlook?
  2. When making a sideways bookshelf, what special considerations should I be keeping in mind?
  3. What materials should I be using? Any wood and or screws or are there specific types that are best?


Diagramo of what I am describing

  • 1
    I think @EliIser's Answer gives you a really good starting point but FFR you're asking way too much here — there are seven question marks in the body of your Q, and three or four of those queries could be a separate Question here if asked the right way (assuming no previous Q&As cover that topic).
    – Graphus
    Commented Apr 11, 2021 at 15:35
  • If you do end up just screwing this together you could do with having a look at some guidance to how to pre-drill for screws, we have a previous Q&A here but that's just the basics. There are more wrinkles than this drilling this close to the ends of boards, so it would be worth your time doing further reading to help prevent the risk of splits (regardless of the material chosen).
    – Graphus
    Commented Apr 11, 2021 at 15:40

2 Answers 2


Your main issue is the large span for the shelves. Plugging in your dimensions into The Sagulator gives a sag of over 1/4" with pine, a tad under 1/4" with oak and around an inch for particle board or MDF.

The easiest way to reduce the sag is to have more support for the shelves. Even a single support in the middle (which reduces the span from 85" to 42.5") yields an acceptable sag. Two supports at 28" apart will be even better, allowing use of thinner or weaker shelf material.

If the bottom of the bookcase sits directly on the floor (i.e. without legs), the shelf supports can simply be 10.5" tall pieces of wood placed between the two shelves and between the bottom shelf and the bottom of the bookcase (no need to have the support between the top shelf and the top of the bookcase, unless you plan to use the top to store things as well (which from your description you can't)).

A simple construction of pieces of wood cut to length and then screwed together would be perfectly serviceable. Pre-drill the screw holes to avoid the wood splitting.

Finally, if you are planning on using pine boards from the big box store, note that a 1x12 board is actually 3/4" thick and 11-1/4" wide, so keep that in mind when making the cuts to length.

  • 1/4" for pine? What weight of books did you assume here? It kinda doesn't matter since a centre support as you've recommended greatly reduces excessive sagging (and creative stacking can eliminate it entirely) but FWIW I got a computed total sag of 0.21" for white oak, and this could well be with an under-estimated load given the shelf depth here.
    – Graphus
    Commented Apr 11, 2021 at 15:36
  • @Graphus Using the suggested 30 lbs per foot. You're right that it might be under-estimating. A 12" deep shelf would temp the user to double stack books, doubling the weight
    – Eli Iser
    Commented Apr 11, 2021 at 18:03

There are a lot of issues to consider in this project.

  • It is not clear how much experience you have nor what tools you have to work with so it is difficult to give specific advice on how to proceed.
  • The shelf layout limits the height of books you can store. You may want to consider varying the height of the shelves such that one shelf handles taller books and another only handles paperbacks, if that works for your collection.
  • The connection of the shelves to the sides is important. You can screw them into the side panels, but if the shelves are positively supported in a dado you get better overall support and weight distribution without additional tear out stress at the screw locations. As an alternative you could also provide shelf cleats attached to the sides that serve to support the shelf. Glued dado connections are much better and will not require any screws, but remember that glue connections do not work well for end grain.
  • Intermediate supports will help prevent sagging across the length of the shelves. I would suggest two locations extending the full height of the shelf unit at each location.
  • The back panel is important to eliminate racking of the assembly to either side. It can be attached to the shelf structure with screw along the perimeter of the assembly every 12-16". (Screwing it to the shelves as well will help with stability, but will not help much in carrying the weight of the books.)
  • Your question suggests that this unit will fit in a recess. If so, measure carefully to insure that the opening is uniform so that the unit can be slid in. Do not make the unit too close in size to the opening to allow for any irregularities in the enclosure. I would suggest that the assembly be at least 1/2" to 1" smaller in vertical and horizontal directions to allow it to be moved into place. You can close the perimeter gaps using wood trim, much like is used around a wood door frame.

Hope this helps. As you refine your design, fell free to ask new, specific questions to get more focused answers.

  • Instead of locking yourself into fixed shelf heights when building it, I'd suggest resting the middle shelves on metal dowels so that you can adjust their heights afterwards without having to completely dismantle it. You'll definitely want to split the shelves so they don't go all the way across if you do this. Commented Apr 11, 2021 at 23:33
  • @DanIsFiddlingByFirelight Yep, that works too. Eli Iser never says the thickness of the back panel, but I assumed it might be thin, say 1/4". To work, the back panel should be thicker (1/2-3/4") to support the weight.
    – Ashlar
    Commented Apr 12, 2021 at 1:58
  • Do you think it's a better idea to just split this up into 3 separate bookshelves and lose like 2'' to extra walls in the middle?
    – Moish
    Commented Apr 12, 2021 at 6:39
  • +1, although I think really this should be closed and the OP should ask multiple Qs here (or just ask on a forum where he can get fuller responses about all the various issues, as well as easier help with the [inevitable] follow-on queries).
    – Graphus
    Commented Apr 12, 2021 at 6:56
  • Re. screwing a back to the shelves not helping much, I think you'd be surprised — q.v. the weight-carrying capacity of pegboard. This is just basic hardboard, but sheets of modest thickness can end up supporting more than a hundred pounds of tools.... in effect screwing into the shelves can basically match the stiffening effect of a front-edge strip. So the difference is (can be) significant.
    – Graphus
    Commented Apr 12, 2021 at 7:00

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