Can you Pour Concrete Around a Timber Post?
I’m trying to use a 6×6 Timber post instead of a lally column. Problem is I want to put it in before my slab is poured. There is a concrete footing there now but they will eventually pour 4″ of concrete over that. How can I put the post in before the slab is done? I assume its not a good idea to just bury the timber post in the slab?
Hi Cory, thank you for your question.
You are right in your assumption that you should not pour around the post. Concrete experiences fractures quite often, especially microfractures around points of varying stress (i.e. at the edge of a post). Additionally, any moisture/water that may enter your basement will probably get into the post. These issues combined create a significant rot problem, as water can get to the post and the post is not able to breath, being surrounded by concrete.
To remedy this, you will want to look for a post standoff. You can usually cast them directly into the slab/pour, although I believe some of the post bases rely on the compressive strength of the concrete for the vertical support, so if you are planning to build and load the post before the concrete floor is poured I would have a local building inspector confirm that you are using an appropriate post base.
Here is a link to Simpson StrongTie’s website, they make all manner of standoffs and I think you could find what you’re looking for at a cheap price:
If you are interested in how timber posts rot, here an interesting written a little while ago following a demo of a structure that we raised that was encased in a stone veneer, and not allowed to breath. The timber sat with moisture all around it and just rotted away.
Hope this helps,
Matthew McGinnis, EIT
Junior Timber Frame Engineer
Vermont Timber Works
We build a porch over concrete with wood post , now we need to have 6 inches of new concrete poured on top Of the old concrete as they left it to low from the door . We now learned we need to protect the wood post How can we protect the post ? Now they are ready to set forms help !!
Pouring concrete around a time post is not recommended because the bottom of the post will rot out. You are better off shoring up the existing structure, cutting the post bottom to the new height, pouring the concrete underneath, then removing the shoring.
Good luck with your project,
Designer | CFO | Owner
Vermont Timber Works, Inc.