A common design question when working with wood posts and concrete (or stone) is: how do you anchor posts to the concrete? Honestly, if we’re talking about a large structure with a lot of weight, gravity does most of the work and you don’t need a specific connection. A concrete post anchor may be necessary in a variety of situations, however. Here is a particularly slick way to anchor wood posts to concrete using a very discrete piece of hardware.
Super Strong and Hidden Concrete Post Anchors
Like I said above, if you’re building a heavy structure on stone or concrete piers, it’s unlikely you really need to secure the wood posts down. (Our straw bale & timber frame house is a good example — the entire structure sits on concrete piers, but a tie-down would be totally overkill. The weight of the house is massive. There’s no way uplift would ever occur. If it does, we have other more serious things to worry about.)
Perhaps you’re building an open air timber frame pavilion, or some other structure and you need to take uplift into account. I’d like to draw attention to a particular piece of hardware I’ve used for such an occasion with good success.
The product name is Timberlinx, and these connectors serve many roles in timber construction, not least of which is a concrete post anchor. I’ll focus on what is called the A475, one of the pieces of hardware that is used for such a purpose.
The best thing about the hardware is this — they are almost completely hidden from view. No ugly brackets, no concrete screws, nothing is visible when all is said and done. Ideal. Check out the photo below to see how it works.
How to Use a Timberlinx Concrete Post Anchor
The only challenge with using Timberlinx is that you have to be really accurate to get a proper fit… but hey, you should always be as accurate as possible, so no worries, right? They’re really not so difficult to use, but it could be a little intimidating at first.
Here’s how they work. Basically, you secure a piece of 7/8″ all-thread into your concrete or stone. Drill a 1″ hole into the cured concrete, cut the all-thread to the right length, and use epoxy to secure it in the hole. Of course, you must properly locate exactly where the all-thread must go. (And no, I would not install the all-thread in fresh concrete.)
When you’re ready to secure your wood post, you twist the metal collar on the all-thread. You’ll need to drill a corresponding hole in the bottom of your post, and in the side for the expanding pin. (Again, you’ll need to precisely locate where on the post bottom this hole should be drilled. Drill it at 1.5″ diameter to give yourself a little bit of wiggle room.)
When the post is lifted into position and seated on the all-thread with collar, you then insert the expanding pin in the horizontal hole and through the collar and use an allen key to open up the pin. The pin will expand and suck the post down to the concrete. Viola. Done.
All of this is totally hidden inside of the wood. You can even plug the horizontal hole so that nothing whatsoever is visible. Clean, simple, strong. I like it.
The Timberlinx A475 is a bit spendy, but for such a high quality product, you definitely get what you pay for. It works well, and looks way better than pretty much any other concrete post anchor option out there. Important note: the A475 will work with 6×6 or larger posts. Good luck!