wmonroe said:
Hi everyone, I am getting ready to start building a 28x30 pole building garage. I am going to use 6x6x16 posts concreted 4 feet deep in the ground. I have two questions: is 4' deep adequate depth for the posts (8' or less apart)? and I was just recently told that I shouldn't concrete them but instead pack dirt back around the post because the concrete would rot the post, is this true?
Thanks in advance. This is a great site.
Will
Post setting depth depends on frost depth. Where I live it is in the 36"-42" range so we design foundations so they are 48" below grade. Local code is going to require that you go at least as deep as the local frost depth design standard. The building department can tell you what that is.
There are a few schools of thought on the concrete vs. no concrete method for setting a wood post.
Concrete:
- More Stable
- Concrete holds water against the post and doesn't allow for drainage.
- May be code requirement in your area.
No Concrete:
- Allows for water to drain around posts.
- Less expense.
If you go with soil, pack washed gravel at the bottom of each hole before setting the posts - it keeps each post from sitting in water all of the time. I would also use soil that doesn't have any organics in it. Top soil, black dirt, etc. don't have any structural qualities. You'll eventually regret using that kind of soil for backfill.
