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Hello to the great woodworking community!

I'd be grateful for a bit of advice concerning the building out of the following construction:

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I bought the glued dried pine wood already. I will use screws because I want to be able to disassemble it easily on demand. I also want to achieve that cross connections are aligned as a straight plane on the top, as shown on the image, so I have no gaps for the top board. That means I need to cut out the beams one into another to achieve it.

The question is, for the marked joint in the middle of the 2.5m (100") beam, what is the optimal depth that I can cut out the lap-joint on each of the beams in order not to weaken too much neither the top or the bottom beam. Should I cut into the middle of the top beam, or go even more, not to weaken the bottom 2.5 (100") beam which needs all the strength? On top will be a loft bed 160cm wide with not more than total 200-300kg of weight. Here are the two examples, which one would be more appropriate?

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Thank you so much!

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  • Please clarify your specific problem or provide additional details to highlight exactly what you need. As it's currently written, it's hard to tell exactly what you're asking.
    – Community Bot
    Commented Feb 5, 2022 at 14:39
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    Given your spacing and wood sizes, I would recommend no notching. Even then, it might not do a good job of supporting your intended load — only testing will tell. If you had to notch, take no more than 1.5” out of the thinner cross pieces and double the quantity (so they are approximately on 10” centers). Even that might be too weak, which would mean doubling again.
    – Aloysius Defenestrate
    Commented Feb 5, 2022 at 14:55
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    What will the structure be supporting if anything? If there will be items stored on top, will the projected ends need to support weight as well or are they only for esthetics?
    – Jack
    Commented Feb 5, 2022 at 17:57
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    You're going to cantilever some 2x4's about a foot. So, less (way less) than half? The beam should be a 4x6, which you notch into effectively a 4x4, not a 4x4 that becomes a 4x2 sitting the wrong way. - No notches anywhere; add blocking. Or minimal notches; add blocking.
    – Mazura
    Commented Feb 6, 2022 at 4:54
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    I’m voting to close this question because the two examples are the same. There is no question.
    – Rohit Gupta
    Commented Jan 21 at 20:57

1 Answer 1

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I wouldn't go more than 1/2 the thickness of the "narrowest" pieces. Based on your drawings, that looks like ~1.5". Your wood is going to be strongest where it isn't cut, so you'll want to leave as much uncut as possible.

The strength (or weakness) will depend largely on the precision with which the joints are cut. What you want to achieve is the lap joint fitting together as cleanly as possible.

Any "slop" or gaps in the lap joint takes away from the overall strength of the "platform". It's the cross pieces fitting tightly into the joint that makes up for the fact that you cut some of the wood away from the other "beams".

Not using glue for these joints will greatly diminish the overall strength of the "platform" as well.

It's unclear how you intend to affix the platform to the legs, but some version of a lap joint should work well for that as well. Also, you might want to consider some kind of secondary bracing or crossmembers if the "legs" are not going to be fastened to the walls to prevent the structure from racking. Even small movement will distort the joints and weaken the structure.

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  • Thank you! I will use no more than 1/2 then and I'll try to make it precise. Your answer is very helpful. I will also see on-the-go how I can compromise for the fact that there is no glue. For the legs I still don't know, I have a few ideas. Let's see. If needed, I'll use secondary bracing or fix a plane board on top of everything to hold it square.
    – Hrvoje Golcic
    Commented Feb 6, 2022 at 10:18
  • How do you handle the noise from the rubbing of the wood joints?
    – Lee Sam
    Commented Feb 6, 2022 at 16:41
  • @LeeSam I've heard that glue is good for that...
    – gnicko
    Commented Feb 7, 2022 at 1:53

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