When making butt joints for corners, say, for small little cabinets to hang on a wall (think medicine cabinet), structurally is there any difference between longer tops and longer sides (I'm using biscuits and glue, and I find I like using cleats attached to the inside top for hanging)?

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I personally prefer the look of longer tops and bottoms especially if I intend to use the top surface as a shelf, but having longer sides is much easier for me to construct since all the horizontals are the same length, and gives a slightly easier order of assembly.

A lesser question: In addition to structural properties, is there any traditional/historical stylistic tendency for longer tops vs. sides?

I realize the butt joint is a boring joint but in my limited experience I find that I keep agonizing over which to choose.

  • if you can't decide, just do 45 degree angles as a compromise – CRABOLO Oct 24 '15 at 1:34
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    If it is going to be that small I dont think this matters. Do whatever you want. – Matt Oct 24 '15 at 2:45

When making butt joints for corners... structurally is there any difference between longer tops and longer sides [using biscuits and glue]

Yes, with longer sides it would be stronger. The reasons being:

  • for the glue line to be broken it has to shear through at 0°, versus being pulled apart at 90° which is much easier (although it must be stated, still very difficult if made properly);
  • and with biscuits they'd have to be snapped across their centre for the joint to break, rather than simply pulled free from their slots which is obviously much easier in principle (again, still very difficult).

For very large constructions that need to hold up a lot of inherent weight (the weight of the piece itself), even before the added load of items stored inside, longer sides would be far preferable. But for smaller pieces I suspect it doesn't matter in practice.

One additional advantage to longer sides is pure aesthetic: in this case (wall-mounted item) there's less end grain visible in the finished piece, which is considered very desirable by many woodworkers although some are less fussy about this.

A lesser question: In addition to structural properties, is there any traditional/historical stylistic tendency for longer tops vs. sides?

It wouldn't have been common for boxes of this basic construction to have been built historically as they didn't often rely on 90° butt joints, but in more recent tradition where dowels have been widely used I'm fairly sure longer sides would have been the preferred orientation for exactly the same reasons as stated above for biscuits, where again the dowels can be pulled free more easily than snapped cleanly in two.

It shouldn't go unsaid though that many traditional woodworking techniques go toward making the strongest piece possible for any given joint type, and it's widely acknowledged that this means much furniture has over-engineered joints, i.e. much stronger than truly needed.

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    Thanks. And if it is supported from the bottom instead of hung from the top, I'd expect longer tops to be stronger (if you are placing static load on the top) since you're not stressing the glue or biscuits at all, you're just compressing the sides. And I can use a blind dado (I am presuming that is what you'd call it? I'm just piecing together words I'm learning) if I want that kind of strength for shelves but with a butt joint look on the front. – Jason C Oct 25 '15 at 15:09
  • @JasonC, with the long top it would be strong at that position with weight placed upon the top of the cabinet, but you're unlikely to pack much weight up there I would have thought. And it would take significant weight to cause any problem to the biscuits and glue at the sides if you went with long sides. Now as I say either layout could be strong enough in practice, but if you're after strongest overall then exactly as in your second drawing is the one to pick. – Graphus Oct 25 '15 at 19:56
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    @JasonC, ran out of space in the previous comment. Re. joints more generally, if you want to bone up on terminology, as well as get many tips on how to form them using hand tools, I highly recommend Woodwork Joints by William Fairham, which is considered a classic on the subject. You can download the HTML copy of this for free from Project Gutenberg here so you can refer to it offline any time you like. – Graphus Oct 25 '15 at 19:58

If it is going to be that small then I think either configuration would be more than sufficient with biscuits. Butt joints are considered one of the weakest but the biscuits should be gluing face to face (grain I mean). That way you are overcoming the butt joints main drawback.

For what it is worth I have an older medicine cabinet and it uses rabbet and a dado joint (might have a more elegant name) for the frame and shelf. The joint is exposed from the front and back just like in the below photo. The door is a simple mirror with a mitre joint frame. So in essence mine matches you longer sides picture.

Rabbet and dado

  • Structurally, would it matter for a larger piece like, say, a large bookcase or an entertainment center? – Jason C Oct 24 '15 at 3:06
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    Most modern bookcases, like Ikea'a for example, just have take down hardware and butt joints and they hold just fine. Albeit not the best setup. I wouldnt personally use them but they would work. With the weight of books and some electronics stronger joints would be a good idea as well as cross braces to prevent racking. Metal brackets can work for this as well. You will find other posts about this sort of thing say that you dont need to over think this. – Matt Oct 24 '15 at 3:21

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