How Do I Build a Shed on Sonotube Posts?

Building a shed can be a complex task, especially when constructing a shed from scratch. Hardware stores sell sheds in kits that almost anyone can assemble. The problem that people run into when building a shed is how to anchor the shed to the ground. Building a shed on Sonotube posts is one option for homeowners who are willing to spend the time constructing a shed themselves. A variety of products are similar to Sonotubes and serve the same function. With a little bit of research, time and planning, you can construct your shed with the help of some friends.

Concrete Mix

Sonotube form

Water

Shovel

Pea gravel

Threaded rods with washers and nuts

Determine the size of your foundation.

If you are purchasing your shed from a hardware store, look at the specifications to figure out the dimensions of the floor. If you are designing the shed yourself, determine what size your floor should be.

Figure out how many forms you need.

You need at least want one post in each corner of the shed. If your shed is longer than 10 feet in one direction, you should probably have another post at the midpoint. For example, an 8-foot by 12-foot shed would have six posts, one in each of the four corners and two at the midpoints on the 12-foot side.

Stake out the location of the shed in your yard before digging.

The holes must be aligned. Use string to lay out your holes.

Determine how deep you want your tubes.

Dig down to the frost line before pouring the concrete. Frost lines vary depending on your region. Start by assuming you want a 10-inch diameter Sonotube that is about 3 feet deep.

Dig the holes for the Sonotubes using a posthole digger. Dig down a few inches below the depth of your tubes.

A shovel is also fine for digging, but renting a gas posthole digger could save you valuable time and energy.

Lay down pea gravel at the bottom of the hole. This will help drain water around the bottom of the concrete piers.

Set the Sonotubes in place. It is extremely important to take your time to ensure that each tube is level. This directly affects the evenness of your shed's floor.

Read and follow the instructions for mixing and clocking the curing time of the concrete; any type of concrete will work.

Mix the concrete and pour into the Sonotubes.

Set threaded rods in the concrete while it is still wet. The threaded rods help anchor the floor to the slab. As long as the concrete is wet, you can set the threaded rods at the same depth.

Place your floor framing over the concrete Sonotubes once the concrete has dried.

Anchor the floor to the threaded rods by using washers and nuts.

Double check to make sure everything is level before pouring concrete.

Depending on the type of shed you purchase, the way you anchor the Sonotubes to the floor may vary.

Plan how you want to anchor them before pouring the concrete. Read the instructions that come with your shed to figure out the best way to anchor the floor framing with the Sonotubes.