4 foot steel stakes. Much more expensive.

You could pound some wood stakes into the ground next to the timbers and screw them into the sides. Ideally use pressure treated if you want it to last. I am not sure if they sell pressure treated stakes, but you could make your own if you have a table saw.

Why not use the rebar in a slightly oversized hole, and then pour epoxy down the hole?

This will lock the wood to the rebar, and also prevent the rebar from working it's way out of the wood. And even if the wood did somehow rot away, the rebar would be encased in a "tube" of epoxy and be unable to damage anyone.

Rebar stake the first layer of timbers down, then secure the second layer over top the holes however you want, 10" spikes or GRKs or whatever you are comfortable with. Not much works better for the price than rebar for this kind of thing though. You could also set both layers, drill through, forstner the top of the hole larger, rebar them together deep, and glue a plug over the top.

It should stay well-hidden unless the wood rots away entirely, but you could use 3/4" steel pipe and pipe caps if you wanted to keep everything inherently smooth

If you're weird about using rebar through the entire thing you could use 8" exterior wood screws and attach them to each other that way

3/4 PVC?

Wow, that sounds genius. I think I’m going to try that.

I definitely considered this, but wasn’t sure of the logistics. I have a circular saw though so I might could make them somewhat sloppily.

Thanks for the advice

I like that idea. I was thinking of getting a long plastic stake for growing trees and cutting it to size but this would probably be better

Weld a circular disc on the top of the rebar stakes, 3-4” in diameter. Basically turn it into a welded on rebar cap

Follow up, what product would you suggest for this? There are so many options when looking at Home Depot and most are little tubes for smaller applications. Is there anything in liquid form I could just pour into the hole?

We use 3/4 PVC like you would use rebar in the front yard years ago. The PVC outlasted the timbers.

We used a paddle bit, then just tapped the PVC down with a mallet slowly.

I capped all my rebar holes with 1/2” diameter 1 1/2” long carriage bolts, secured with liquid nails. They are cheap and aesthetic.

You could just use some 8-in nails That's what I did worked great. Or honestly if you pre-drill you could drive oak pegs through them into the ground. I would use the nails

Go to a boating supply store like West Marine. You can buy one gallon and two gallon buckets of two-part epoxy. It's not cheap.

You can also order it from Amazon, I would think.

Thank you I like this idea

I used to work for a municipal parks dept and the method you described is honestly the standard way of doing it. The "fancier" (overpriced & over-engineered) way to cut the this rug is to pay out the nose for injection molded plastic from Sweden that ends up becoming brittle in 10-20 years anyway. Even then, you still use rebar to stake it in place.

The timbers are secured to each other by stacking 2-3 layers and Lincoln-logging them. Drive bars at the joints and every few feet.

Parks departments really don't like lawsuits and their administrators typically get certifications on all matters playground. If it's good enough for them it's good enough for me.

Lmk if you have any other questions. Haven't done that work in a bit but I'd be happy to help however!

I used a ton for my yard including tiered sections 2-3 high.

Rebar into the ground, ~2 per 8’ section, 2-3’ long depending on how many Timbers you’re going through.

I highly recommend headlok to fasten them together where you make a 90 degree turn, and/or throw a few in for tiered sections. They’re not cheap fasteners but are very strong and hold up well, available in multiple lengths.

This. I did rebar only through the first timbers on the ground. Then, i staggered the second layer so the rebar was covered and used lag bolts to fasten the two layers. Kids used the area for 10 years and never had an issue.

Bonus: If you want to reconfigure the area you just lift the timbers up off the rebar, reposition, and drive the rebar into the new area and slip the bottom timber with the hole over it.

You can get Timberlok screws at the home center.

https://www.homedepot.com/b/Hardware-Fasteners-Screws/TimberLOK/N-5yc1vZc2b0Zcbp

Just counter sink the rebar and plug the holes with a wood dowel - or just countersink the rebar and do nothing.

Out of curiosity, if the rebar is completely hidden within the 4x4's or 6x6's, what is your rationale for not wanting them? They're tailor made to secure a timber wall.

There was a great video from a furniture maker on how titebond wood glue is stronger then wood. Epoxy will work, but it will be too hard/stiff/stronger then needed. Something with give will do better in wood.

Consider masking off and encapsulating just the end. Too big of a volume curing together will get too hot and can start a fire.

Epoxy does get hot when curing, but I doubt it's hot enough to start a fire. The rebar would act as a heatsink regardless.

I still think epoxy is a better choice, because it needs to bond to both metal and wood, and I don't think Titebond grabs well onto metal.

You’re right, depending on the diameter of the rebar hole it probably wouldn’t get too hot. Epoxy would work, it just may not be the best.

Also yes epoxy will adhere better to the metal than many other adhesives. However this is a potted application where cohesion and bulk material properties will dominate the strength. The ribbing on rebar will have to crack through the adhesive before any adhesive strength is tested.

Consider the higher density great stuff (polyurethane foam) for protecting the rebar and filling gaps. It’s designed to help support windows and doors and would probably be much easier to use here

"help support" is not nearly the same as "firmly bond to" and if you have ever compared the strength of the two, it's easy to crack off the excess Great Stuff foam, but I've never been able to crack epoxy without using massive quantities of leverage. Plus this will be outside, and UV radiation from sunlight massively degrades polyurethane foam, so that's another reason I would vote against it.

Dig out a bed about 2” wider than the timber and fill this with level compacted sand. Place the timbers in the sand so that they do not move. Rebar doesn’t creep out or stick out when done correctly so that’s not a problem but preferences are king and you want what you want. So the sand will keep them generally in place and you may have to move them back into place if they are forced out of place by fought play or intentional movement. They are safe and should remain in place even with children walking on them or jumping on them. I have seen timbers linked together with eye hooks to keep them in line AND in sand and that makes it more difficult for one to get kicked out of place and it’s not unsightly. I have made angle iron fasteners for the bottom of timbers in jobs I have done and pointed the 30cm iron to sink into the ground. I powder coated it for appearances AND rust prevention (since they were underneath and never seen). These prevent the possible creep of a bar pounded down through the timber into the ground…though I have done this MOST and have never had one creep out. Either way I would powder coat or at least smear with tar to keep the rust from eating it away over the years. A job done well is a job done once.