What size auger, add concrete?

[gstrom99]

Several years ago, the "machine shed" (3 sided loafing barn style 24' x 50') collapsed. I got it all taken apart, but left the standing back wall. I'm now think of putting a smaller one (20' x 30') in its place. The back wall has three posts busted at ground level. I don't want take the walls apart and want to put in 4x4's to "sister" to the existing posts, then have the shed built next to and maybe attach to the standing wall. There is a building on the left side and I'd have a right side wall built. Will obviously have to move the car and clean out the debris first.

I have a 3 point post hole digger (new to me - never used one), and 3 augers - 6", 9" and 12".

What size auger should I use for planting the 4x4 posts? Add concrete, or no?

 

[EddieWalker]

In my experience, the bigger the hole the easier it is to get all the posts lined up perfectly straight. Even with a 12-inch auger, odds are good that you will have to modify some of your holes with a clamshell digger to get everything lined up.

Ever since the process for treated wood change, 4x4's became extremely prone to twisting and warping once they are in the ground. Unless you have posts that have dried out for at least half a year, they will be saturated with water. As they dry out, they twist.

At the very least you should consider 4x6's posts with 6x6's being even better.

All treated posts will rot at ground level if water is allowed to sit there over time. Be sure to build up the concrete around the post so water sheds away from it.

 

[nybirdman]

In our neck of the woods(Northern NY) you do not put concrete around posts,frost will heave them.
Four foot dig,pad at base and a plastic sleeve around post(Home Depot has them).

 

[gstrom99]

What's the plastic sleeve for, if not to hold concrete?

The new shed will get 6x6 posts I think (leaving that up to the builder) and will look similar to this (stolen internet pic).

 

[paulsharvey]

What's the plastic sleeve for, if not to hold concrete?

The new shed will get 6x6 posts I think (leaving that up to the builder) and will look similar to this (stolen internet pic).

View attachment 5536353

You can do a sonotube footer, with an Simpson Strongtie ABU66 on the footer to receive the 6x6. The 6x6 is not in contact with the concrete or below ground. I "think" its an ABU66Z, if in contact with pressure treated wood, but things may have changed? I prefer wet set bolt, but you can you redheads and then you have a couple inches of adjustment to the the post bases 100% lined up.