Milling locust for construction lumber-strength?

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IHDiesel73L

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I have a whole mess of locust on my property including some very tall and very straight 18"+ diameter trees. My buddy who has a Wood Miser will be coming over once we get a few of them on the ground and stacked and will mill whatever I want for $0.55/board foot. When considering what types of lumber I'm milling and what size (6x6 posts, 6x8 beams, etc...) pieces, it would be helpful to know if locust is on par with douglas fir, southern yellow pine or some other widely used species for dimensional lumber especially for spans, etc... Anybody know an online resource for this? One of the projects I have in mind is a 16' x 6' open sided woodshed with locust posts. I'm wondering how far I could span without a post if we milled say a 4x12 beam or something of that nature.
 
If it's Black Locust, it's about on par with Hickory in terms of strength. Slightly stronger than Oaks... https://www.wood-database.com/black-locust/

Span will depend on the load on the beam. If there's no load on the beam, you could span 30' without issue if the tree is long and straight enough for a 30' 4x12... but I'm betting you're going to have trusses or rafters hanging on it, in which case, you'll need to know your roof load (lb/sq. ft.; and the rafter/truss length). You'll like likely need an engineer (PE or Architect) to help with those calcs. I'm a mechanical engineer, but you'll need someone to review drawings, and if you plan on permitting it, stamp said drawings, not something that can be done remote.
 
I would also add, it's MUCH stronger than any fir or pine. In fact, it is considered by most to have the greatest beam strength of any North American grown tree (native at least). It's also one of, if not THE most rot resistant woods in existence. We have fence posts on our farm that are >100 years old, black locust, still sturdy and standing... the pine posts last 10 years at best... natives used the wood to make bows, some of which have been found somewhat intact centuries later.

Black Locust is a wonderfully useful wood. The tree's however are horribly invasive, and spread like wildfire, and when you cut this one down, expect to see shoots sprouting up all around it for a few years after (if you cut them all down quickly, the rest of the tree will die in 3-5 years).

Keep whatever brush and small wood you can. A full cord of black locust firewood has the same BTU value as a ton of anthracite coal. It is my favorite firewood to burn (cutting and splitting, not so much, it's heavy as hell). The flowers are wonderfully fragrant as well.
 
If it's Black Locust, it's about on par with Hickory in terms of strength. Slightly stronger than Oaks... https://www.wood-database.com/black-locust/ Span will depend on the load on the beam. If there's no load on the beam, you could span 30' without issue if the tree is long and straight enough for a 30' 4x12... but I'm betting you're going to have trusses or rafters hanging on it, in which case, you'll need to know your roof load (lb/sq. ft.; and the rafter/truss length). You'll like likely need an engineer (PE or Architect) to help with those calcs. I'm a mechanical engineer, but you'll need someone to review drawings, and if you plan on permitting it, stamp said drawings, not something that can be done remote.

Thanks for that link. This is going to be a pretty simple structure:
A2Fbr8Gl.jpg

Four posts in the ground at each corner and two beams to support the rafters above-probably spaced 24" OC with purlins and steel roofing. Snow load around here is 30lbs/psf. According to the Wood Database the elastic modulus of black locust is 14% greater than that of douglas fir, so that's a good sign. No permits or engineering needed, just looking to put up a low cost open sided covered shelter for firewood inexpensively using wood from the property. In terms of what my buddy is charging me, a 6x6x12 locust post will cost me less than $20.00. The same post in pressure treated pine from the local box store is $36.00. From the looks of the locust posts my neighbor has on his farm (placed in the ground long before he bought the place 45 years ago) locust is every bit as good if not better than copper-azole treated softwood.

I would also add, it's MUCH stronger than any fir or pine. In fact, it is considered by most to have the greatest beam strength of any North American grown tree (native at least). It's also one of, if not THE most rot resistant woods in existence. We have fence posts on our farm that are >100 years old, black locust, still sturdy and standing... the pine posts last 10 years at best... natives used the wood to make bows, some of which have been found somewhat intact centuries later.

Black Locust is a wonderfully useful wood. The tree's however are horribly invasive, and spread like wildfire, and when you cut this one down, expect to see shoots sprouting up all around it for a few years after (if you cut them all down quickly, the rest of the tree will die in 3-5 years).

Keep whatever brush and small wood you can. A full cord of black locust firewood has the same BTU value as a ton of anthracite coal. It is my favorite firewood to burn (cutting and splitting, not so much, it's heavy as hell). The flowers are wonderfully fragrant as well.

LOL...we were posting at the same time and pretty much said the exact same thing. Up until now I've only ever used locust for firewood. We bought this place almost three years ago but heated our last house primarily with wood. I used to love getting my hands on locust whenever I could. Very much looking forward to building with it and burning whatever is too small/too twisty for lumber.
 
Is it black locust or honey locust? I note "If it's Black Locust" Aren't locust posts supposed to last better if cured for a while before set into the ground?

Black locust-I looked at the difference between black and honey and black is much stronger. As for the curing I don't know. I will say this. I just split a bunch of locust that came down almost exactly two years ago. I bucked it then and left it laying where it fell. Other than the bark falling off the wood was still rock solid. Other species would have been a spongy mess after all this time sitting in the dirt with grass growing up around it.
 

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