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I have a lot of well-dried branches and I was wondering whether it was possible to turn them into constructional lumber by gluing them together as follows:

  1. cut them into equal length parts of about 20 / 30 cm
  2. square them so they all have the same thickness (about as thick as a finger)
  3. glue them all together in a brick pattern

Would this glued together board be as strong as plates from tree trunks? By which I mean: could it be use constructionally?

And if so, why aren't those kind of board produced on a large scale? I suppose it's better for the planet if only cut off branches are used.

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Structural lumber has continuous, well connected fibers running through the entire length of the board. Cutting those cells into 30cm/11" segments will significantly decrease the overall strength of the board despite the overlap. The strength of such a composite beam would vary greatly depending upon the profile of the wood segmnts and the types of glue used, but would most likely be significantly weaker.

Your idea, however, closely matches the idea behind OSB (Oriented strand boards in which thin scraps of wood are pressed into a plywood sheet and used as sheathing in many buildings. OSB is not used in structural beams. On the other hand, engineered wood trusses made of laminated wood sheets (plywood) can be significantly stronger/more economic than standard wood studs and joists. IN general, the wood industry wastes very little of the tree when it manufactures wood products.

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    I think 30cm/11" segments are problably too short as well, but in general what the question is asking about is very common. It's called gluelam short for glued laminated timber en.wikipedia.org/wiki/Glued_laminated_timber You need some egineering expertise to determine the strength of the product, but as you mentioned laminated products can be significantly stronger because they can actually compensate for defects in a single piece of wood and the wood fibers go in slightly different directions.
    – T. M.
    Aug 19, 2019 at 15:54
  • OSB is used in structural beams. They're called "I-joists". They're basically two beams of traditional wood joined by a web of OSB. en.wikipedia.org/wiki/I-joist
    – SaSSafraS1232
    Aug 21, 2019 at 15:56
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In basic outline there's no real problem with what you want to do, after all these days many panels are made in somewhat this way, except that the wood is from branches.

Branch wood, unlike the majority of trunk wood, is nearly all what's called reaction wood so it has lots of internal stress. In branches the wood that originally was on top is in tension while the underside was under compression, and when these stresses are released by cutting and shaping you get signifiant warping issues. This is why branch wood isn't generally harvested commercially for use in any length, but is instead flaked, chipped or pulped e.g. for use in manufactured boards or for paper production.

It's certainly possible to utilise some of the wood from branches but not for this. Turning projects, stickmaking, tool handles and dowels or pegs are some of the possible uses for it.

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    I agree with your points on warping in branch wood, but I think laminating thinner pieces with a strong adhesive would could actually compensate for the warping issues. Especially if the OP can mill pieces that don't warp immediately as soon as they are milled due to being reaction wood. en.wikipedia.org/wiki/Reaction_wood
    – T. M.
    Aug 19, 2019 at 16:00
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    Even if they do warp immediately I don't see any issue here. If they're laminated together flat then they'll stay that way. Think about a bent lamination. His idea was to laminate pieces ~1/2" thick together to get "construction" material, so probably 3 layers thick and 7 across to get a 2x4? If you used the right glue I think it would end up more or less as strong and stable as a construction grade 2x4. Of course it wouldn't be up to code for actual use in a structure, but for other purposes I think it would be fine.
    – SaSSafraS1232
    Aug 19, 2019 at 21:59
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    @T.M., reaction wood is legendarily unstable, and it's not just the potential for warping at time of build that one need be concerned with, it has great potential to warp down the line (here, unpredictably, in random spots). Anyway, the key part of the Question for me is "Would this glued together board be as strong as plates from tree trunks?" and given other variables (doesn't glue as well, every glue joint won't be max strength) an unreserved answer of yes can't be given. Especially as the intended use is construction lumber where strength/stability isn't just desirable it could be vital.
    – Graphus
    Aug 20, 2019 at 7:22
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    @SaSSafraS1232, I agree for other purposes this could actually be fine, since at worst you'd be looking at a warped piece of your own furniture. It was the stated use as construction lumber that I think warrants an answer of a flat no.
    – Graphus
    Aug 20, 2019 at 7:39

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