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I am planning on building my first woodworking bench based on Rex Kreuger's Quick-stack design. Since I live in Hawaii, the only dry untreated construction lumber available are DF 2x4x8's. The local building code mandates borate pressure treated lumber for all framing, so this is all the home centers sell.

I am currently planning to build the laminated 2x4 top from untreated 2x4's and finishing with Danish oil after planing flat.

Is it ok to build the base structure out of the available treated 2x6s and 2x12s? Or should I stick to the untreated 2x4s? I'm not exactly sure how to replace the 2x12 stretchers except by edge gluing 2x4s.

If I do opt for treated lumber, how long do I need to let it dry to equilibrate for 70% relative humidity?

This bench will live outdoors in a covered area, however, it will get a fair amount of sun and occasional storm rains. Maybe the treated base will hold up better in this climate and keep away the termites? I could always paint it to hide the appearance of the green tinted lumber.

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  • "Should I build the base structure out of the available treated 2x6's and 2x12'? Or should I stick to the untreated 2x4's." Someone should have highlighted already that this is directly asking for opinions, which is the wrong way to ask something on SE (we're directly instructed us to avoid subjective questions). There's plenty of other stuff worth picking up on in an Answer so I'll do the edit, so that I can respond to all of it in one shot in my Answer.
    – Graphus
    Commented Aug 22, 2022 at 18:03

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The local building code mandates borate pressure treated lumber for all framing, so this is all the home centers sell.

There are other sources of wood than home centres! If you go to a dedicated lumber yard not only will you generally find better wood of any given type you'll be paying lower prices for it. In addition I'd be shocked if you don't find a better selection1, which could render the main part of your Question moot :-)

Is it ok to build the base structure out of the available treated 2x6s and 2x12s? Or should I stick to the untreated 2x4s?

Yes. There are many workbenches out there with the understructure, and occasionally the entire workbench, made out of PT wood of various kinds.

If I do opt for treated lumber, how long do I need to let it dry to equilibrate for 70% relative humidity?

This should be a separate Question, because it's a separate question. But coincidentally I tackled this in an Answer just a few days ago.

From the Comments:

Hopefully the PT wood takes up the glue well enough. I worry because sometimes the borated wood has a waxy feeling on the surface.

If you are forced to use the borated wood if in doubt switch glues, because from reading around online the borax treatment does interfere with the bond formation of PVAs. You could try cleaning the joint surfaces well to lessen the effect, or you could not use glue at all....

There are plenty of workbenches out there where some of the major joints aren't glued. In addition to one of the old-school ways of doing the major leg/stretcher joint, a tusked tenon2, you could peg or drawbore all your joints; pegged correctly or drawbored M&T joints don't require glue.

And of course there are always nuts and bolts or lag screws to consider. Again, plenty of workbenches use some combination of these in their construction (especially for the major joints). Modern construction screws such as GRKs are said to be good enough to replace lag screws, with significantly easier installation, in case you want to look into that (note they may be several times more expensive).

I was thinking of laminating 3 layers of 2x4 or 2x6 to make the legs. This way I can get a free mortise for the stretchers and a little extra mass.

Sound plan3. And if you're doing this you could more easily create a tapered mortise for yet another option for a no-glue stretcher/leg joint using an external wedge, see Sturdy, knock-down workbench on Fine Woodworking (PDF available).

1 A quick Google search located one which lists DF from 2x4 up to 2x12.......

2 One of the notable design details of what we've come to know as the Moravian bench. Paired wedges (AKA folding wedges) can be used to give the same effect.

3 Laminating up for major leg structures can have numerous advantages, one of the major ones for the workbench builder being 'free' mortises as you note. But there are often major savings to be had as well, because in wood pricing generally there are premiums for thickness as well as length (do note this does not always extend to width, allowing the possibility of further savings by buying wider boards such as 2x12s and ripping down to width).

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  • Thanks for you very thorough answer. I did call the lumberyard you mention and was told the untreated DF was very low grade and only suitable for building disposable forms. I guess I should probably go over there and check it out. They also sell clear fir lumber but the price was crazy.
    – Mike
    Commented Aug 22, 2022 at 22:15
  • I love the look of the tusked tenon, but making four of them is pretty intimating at my present skill level. I do like the two dowel alternative that Rex Krueger uses on the design I linked. However, I still need to ensure that the legs will laminate well with treated lumber. I'm trying to avoid fasteners, but I suppose there is no shame if I'm already using construction lumber to save money.
    – Mike
    Commented Aug 22, 2022 at 22:19
  • "I love the look of the tusked tenon, but making four of them is pretty intimating at my present skill level." Sorry I may have over-stressed this part in my enthusiasm to cover the topic fairly well for the benefit of future readers. (FWIW Rex has at least one video on these too, but they're not needed here so just bear it in mind for the future if you want to make use of them.) "I'm trying to avoid fasteners" I was going to say re. laminating the legs you could just screw them together. I think Rex has something on using screws more heavily in one of his other workbench vids!
    – Graphus
    Commented Aug 23, 2022 at 23:55
  • There's probably nothing wrong with screwing the legs together...unless you forget about the screws. I was just modifying the screwed butt joints on my first bench to use tight dados and put a big notch in my 1" chisel with a hidden screw!
    – Mike
    Commented Aug 24, 2022 at 1:38
  • Ouch. But at least it's only a chisel which is easily repaired (assuming you have a grinder or belt sander?) and not a planer or jointer knife! If you did screw together in this case you won't easily forget about the screws as you can arrange for them all to be driven in from the outside so none will be hiding :-)
    – Graphus
    Commented Aug 24, 2022 at 16:27
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Edge-gluing 2x4s should work fine for the stretchers, just make sure they're jointed (perfectly flat against each other) so the glue can do its best work. Any imperfections will weaken the glue joint. Since it's going to be in a sometimes-wet area, at least making the legs out of pressure-treated (PT) lumber is an excellent idea. As for other parts of the base, including the stretchers, PT should be fine as long as the joints are mechanical. If you do want to add glue to strengthen, for example, the dovetails at the top of the legs, definitely contact the manufacturer and see what their opinion is on gluing dried PT lumber. If you're intending on taking the bench apart later, not gluing the dovetails is probably a good idea.

As far as drying - if I have the time, I try to let new wood acclimate to my shop for at least a couple of weeks. At 70% humidity the drying of the borate solution used for pressure treating may take a little longer. Not being from the islands, I can't give you any direct experience, but I've worked in the southeast US during the summer where it can be quite humid for long stretches as well, and PT lumber in direct sunlight with good air circulation around all sides usually dries fairly quickly. Of course, that's assuming it doesn't rain in the meantime...

One more piece of advice: put many coats of oil on your bench, and keep doing it throughout its lifetime. I built my first bench out of hardwood (maple and oak pieces from some old metal-framed pallets I got for free, and laminated plywood for the base), and used boiled linseed oil instead of Danish oil, but I put a ton of oil on the thing, as it just kept absorbing it! In the beginning, you don't need to let it completely dry between coats, so maybe 1-3 coats a day for a week or two, keeping it wet for 15-30 minutes after application, as it'll absorb quickly. Then, a coat or two every week for a couple of months, then a coat or two every month for a year or so, then once a year for life.

Best of luck on your project! Building your own workbench is a tough but very satisfying project.

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  • I was thinking of laminating 3 layers of 2x4 or 2x6 to make the legs. This way I can get a free mortise for the stretchers and a little extra mass. Hopefully the PT wood takes up the glue well enough. I worry because sometimes the borated wood has a waxy feeling on the surface.
    – Mike
    Commented Aug 22, 2022 at 17:38
  • Contact the glue manufacturer, or just google it first. I'm sure you're not the first person to try gluing PT lumber. Of course, there are different methods of pressure treating, so make sure you're comparing apples to apples. But other than that, thicker legs are definitely better!
    – MattDMo
    Commented Aug 22, 2022 at 17:43
  • I will try researching the glue further. Unfortunately Google just throws procedurally generated websites at me that give exactly the same unverifiable information. It sounds like PU glue might be a good alternative.
    – Mike
    Commented Aug 22, 2022 at 22:22
  • @Mike Or epoxy - that stuff will stick to just about anything.
    – MattDMo
    Commented Aug 22, 2022 at 22:23
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Honestly, I don't see any reason not to use the treated lumber for the workbench other than any additional cost that might be in the wood or esthetic value. And since you say it will be out side in the weather, it could help it last longer, since treated wood is done to help it prevent rot and bugs.

(for the base)

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  • Thanks, my old bench is made out of PT lumber and has held up well in the same location. It was not constructed for woodworking though and its time for a fresh start.
    – Mike
    Commented Aug 22, 2022 at 17:35

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