I am building a new wall in my yard. I am putting in 6x6 wood posts to frame out the wall. In order to make sure the posts stay in place, I was told to put cement in the bottom of hole that the posts will be placed in, followed by gravel. Is this the correct procedure? Is there anything else I need to do to ensure that the posts are solid and properly installed?
Shawn U. ~ Tulsa, OK
Hi Shawn. How you build your wall depends a lot on what you plan to use it for -- is it for something structural or is it just a part of your backyard landscaping? A structural wall normally supports something above it such as a roof, a second floor, or a deck and while it doesn't sound like that's what you're constructing, if you are, it should be built according to the building code in Tulsa. Most structural walls are supported by either a concrete footing or a series of concrete piers and they are going to require a building inspection.
If you are building a landscape wall, it still needs to be sturdy, but it doesn't have to be quite as substantial. There are two schools of thought (or possibly more) on how to place the posts for a landscaping wall. I normally dig a deep hole down past the frost line and place a specially designed aluminum pedestal in the bottom to keep the bottom of the post up off the dirt. You can purchase the pedestals at most home improvement stores in the deck and treated lumber section. Once the post is in the hole and secured in the "plumb" position, I pour concrete around the base of the post and then top off the hole with a mixture of compacted dirt and small rocks after the concrete has dried.
I have never had a problem with this method, but some contractors don't like placing concrete around wood posts due to the possibility of trapping moisture against the wood. If this is a concern, dig the hole and pour four to six inches of concrete in the bottom -- you can also purchase prefabricated concrete slabs for this purpose in the same locations as the pedestals. Once the concrete has dried, sit your post in the hole, plumb it up, and then fill the hole with a mixture of dirt and small rocks. Tamp the dirt and rocks against the post base as you go and remember to keep checking that the post hasn't moved out of plumb.
Either of these methods should provide a sturdy and durable base for constructing your landscape wall.