Putting in a column footing isn't always an easy task so here is a short tutorial on a quick common footing for fence posts, landscaping projects, and outdoor play sets.
Step 1: Locate the Center Point of Your Holes
I recommend marking them with a stake, stick, or spray paint. Be sure to measure as many times as you need to. Make sure they are square with one another and in the exact location. Then begin digging the hole. For this example we are using a 4x4 ground treated post and 100lbs of concrete mix per hole. The column is 12 feet long with 30" to be buried in the ground.
The mix chosen is quick setting post mix. Recommended for quick jobs that require minimal structural integrity. Though it is more expensive it sets quickly and eliminates the mixing of concrete which can be costly and time consuming.
To dig the hole for this particular post, depth, and amount of concrete start the shovel 6-8 inches from the center on all sides. Going to the full depth of a spade shovel, then remove the dirt. As seen in the first photo you now have a somewhat perfect circle and the center point will remain in the center for the remainder of the digging.
For a 30" post hole, I recommend using a spade shovel as deep as possible with the same exterior edges. Once the hole is to deep for earth removal begin using a post hole digger. Be sure to use it in the center of the hole. Continue using the post hole digger, most of which have measurements on the side to a depth of 31".
Step 2: Add the Post and Concrete Mix
(quikrete photo credit lowes.com)
Sprinkle concrete mix in the hole before inserting the post. Just enough to cover the bottom helps protect the post even though it is a ground contact post. This is why the hole is dug to 31" rather than 30", providing one inch of coverage at the bottom.
After a light amount of mix has been poured into the hole add the post at its center. Square it up as it needs to be and use a level to ensure both sides are standing straight. Using the level vertically against both sides tilt the post until the bubble falls between the lines. (See photos)
Pour the remainder of the mix into the hole. Two 50 lb. bags are recommended for easier transport and use. The 100 lbs. should come close to the top of the hole.
Once the hole is full of concrete mix ensure the post is still square and level on all sides.
Step 3: Add Water to the Mix
Using two 2x4's support the post on sides perpendicular to one another. Attach each 2x4 with one screw allowing it to rotate and move freely. Once in place press the other end of the 2x4 into the ground to provide stability. This will keep the post level and square after you let it go and while the concrete sets. Again check to ensure the post is level and square after the 2x4's are attached and pressed into the ground.
Add water to the mix as specified on the bag. This may vary depending on the brand.
Once the water is added it may recommend stirring or shoving a stick into the mix to help displace the water, if so then carry out this step. Otherwise after pouring the water onto the mix, cover with dirt. Using the dirt removed from the hole, fill the hole the rest of the way. I also recommend lumping the soil an additional couple inches around the post. This will help shed storm water away from the footing and allow for future displacement of the earth as the soil packs naturally.
Step 4: Continue and Let Set
After one post is set you can begin the rests or do each of the steps simultaneously for each post.
Leave the 2x4's attached for support during the drying process and I recommend a minimum of 24 hours set time before any alterations or attachments of other elements to the columns. The mix is quick set but the longer the concrete has to set on its own without being pulled one way or another the better it will be.