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Community and Q&A

Black Locust Decking

NICK KEENAN | Posted in Green Products and Materials on

I’m looking to build a deck. I’m wondering if anyone here has experience with black locust as a decking material. It’s advertised as being as durable as tropical hardwoods but sustainably grown. I’m particularly interested in what it looks like after a few seasons in the sun.


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  1. bob_swinburne | | #1

    I am using it in Vermont where black locust grows large. I am working with a local sawyer who loves black locust and knows how to slice it up for decking. It is commonly used in urban park projects for decks and benches. My own black locust deck is only a year and a half old and seems to be doing fine. It is a very open and airy design - I don't like using natural wood for decks where it's really closed up underneath. Here is a picture of it new - the only difference now is that it's grayish brown. I used the camo system and installed it fairly green. With the Camo system I can easily replace boards if needed.

    1. user-5904966 | | #13

      Hi Robert,

      I came across this post about Black Locust decking that was sourced locally in Vermont. I am curious if you might be willing to share the name of the local Sawyer you worked with? We are looking to source this material for a project in Stowe, VT.

      Also curious, how has it held up over the past few years? Thanks!

      1. bob_swinburne | | #14

        Jon at Best Wood Vermont in Putney VT. He has a website for contact info. It is holding up very nicely and is excellent for bare feet. There are a few spots were I missed a screw that have pulled up a bit.

  2. burninate | | #2

    Four downsides from my research:
    * It seems to be so dense/strong that it sometimes tends to check, crack & warp from internal stresses that develop either during life or during fast-schedule kiln drying
    * In a lot of the US it starts to rot from the heartwood once the tree is approaching lumber-relevant size, and it can be also attacked by the locust borer and locust leaf miner, but not much else
    * It's so tough it can be difficult to mill/plane/nail/screw into once dry.
    * Because it will grow prolifically from seed or root, it's been regarded as a weed. Even fast-growing locust can't achieve lumber sizes instantaneously. While it can grow straight, if it encounters shading on one side or it gets cut back then it will happily grow crooked. So you want older, even-aged black locust plantations, and you can't just go back to the 1970's and plant them.

    So it can be difficult to get a proper board out of; The price I saw was just slightly lower than black walnut. I think if these downsides didn't exist, black locust would be ubiquitous for its advantages, and we wouldn't have heard of Ipe. If you find a local supplier for inexpensive, dried, stable black locust boards, I'd say go for it.

    1. Andy_Engel | | #3

      I've worked with locust. It's very dense and hard to tool. You'll burn out some drill bits on it. As has been mentioned, longer lengths can be hard to come by. But the stuff I've used on a deck has held up very well for 10 years.

    2. andyfrog | | #4

      Thanks for the info

      Are there any other domestic species you can think of with similar properties to Black Locust?

      1. bd_alex | | #9

        For hard woods- Osage orange, or sassafras might be something to look at depending on your area. White oak might do alright depending on the application/sealing.

  3. dan_saa | | #5

    I've wanted to check out western Juniper

    1. brendanalbano | | #6

      The Sustainable Northwest Wood people are very friendly. If you're in Portland you can go visit them and check it out. I've looked at it before but haven't had an opportunity to use it yet.

      It seems like the closest thing to black locust that is local in the PNW.

  4. wyosky | | #7

    I have a black locust deck in NC, built 4 years ago. It has held up very well with only a couple of center grain boards that warped. The manufacturer's recommended oil based stain seems to have attracted mildew that won't clean off resulting in a blotchy brown/green color on boards exposed to rain. All boards under roof are still like new. If I had a do-over, I would leave black locust unfinished to weather naturally; maybe there would be less mildew staining. Be sure to use end seal to prevent checking/splitting and reapply to accessible/exposed ends if needed. It has been a very low maintenance deck, even in hot/humid/pollen-everywhere NC.

  5. bd_alex | | #8

    I see this is an old thread but I built my back deck out of black locust. It’s on its third season. I used green rough sawn locust from an Amish supplier that I planed on one side. The decking and frame are the same wood. It’s been very stable with minimal shrinkage no twisting. I counter sunk and face screwed all the boards. 5/4x6 decking, 4x4 for the railing posts, 6x6 sunk into the ground, 1x4 for the lattice, 2x8 for the joists.

    I’ve had some checking on the ends but the checking hasn’t gotten worse after the first year. It could just be an issue of using green wood or not sealing the ends properly. I recommend applying an oil based sealant. I’ll include some pictures of what locust looks like sitting outside untreated for couple seasons. I used Australian timber oil and reapplied after the first year and it seems to be holding up pretty well.

    It’s an extremely solid deck, doesn’t feel flimsy at all and it gets lots of comments. It gets used daily and dogs nails or pressure washer don’t leave any marks. I recommend it if you can find the wood. It’s my first project ever so there are a few things I would do different based on experience but I haven’t seen a composite or pressure treated deck that looks good after a few years of sun, rain and snow. BL was a fraction of the cost of a tropical wood and comparable to pressure treated in cost since I planed it myself (probably cheaper than PT now).

    I’ll echo that it’s hard to find lengths longer than 10 or 12 feet around here. Easy enough for decent 8 foot log sections.

  6. vweil | | #10

    We chose black locust for our pool deck after tons of research. Unfortunately, the 50 square feet that the contractor laid down in the fall has bent and checked over the winter and spring. What a disappointment. We are planning to remove it and are looking for alternatives. Expensive mistake.

  7. WVblacklocust | | #11

    You posted in Jan of 2020. What did you end up using and how did it turn out?

    1. Expert Member
      NICK KEENAN | | #12

      I ended up using black locust. I ordered it from a prominent supplier in NC. My pocket review:

      The wood itself is gorgeous, it is very pleasant to the touch and has a nice aroma. It is exceptionally hard and even self-drilling fasteners have to be pre-drilled to avoid snapping them off.

      But it has not been without problems. Some of it is due to the nature of the species, if you look at a black locust tree you can see they don't grow straight and tall like most lumber species. So you're unlikely to get very many long pieces out of a tree, and the wood has a lot of internal stress which means it tends to warp and bend. I don't know how much of my issues were due to the nature of the wood and how much were due to my supplier, but I experienced a lot of warping, and a lot of defects like splitting and boards cut too close to the bark.

      I also got a lot of short pieces. I ordered 1200 linear feet of 5/4x6 in random lengths, and this is what I got:
      Length Count Feet
      3 47 141
      4 50 200
      5 50 250
      6 40 240
      7 21 147
      9 19 171
      10 5 50
      Total 1199

      I thought that was an excessive number of short pieces. Also, those lengths don't work at all with 16" joist spacing, if I'd known I would have done 12" joists. As it was I lost a lot of wood (and time) having to cut down almost every piece.

      I did the edge grooving so I could use hidden fasteners, and that worked well, we'll see how it lasts.

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