How to Install a Precast Concrete Pier Foundation for a Shed

A precast concrete pier foundation is the most stable foundation you can have besides a concrete slab, it is much more stable than skids and you can be sure your shed will be stable for years to come. The piers are embedded in the wet concrete footings and support 4x6 pressure treated timbers. These beams will then support the shed. Once you have laid out your shed, excavate it to a depth of 3 to 4 inches. Then dig holes 10 inches below the frost line for footings. Pour the footings and set the precast piers in the wet concrete. Once the concrete cures, lay down landscape fabric and a gravel drainage bed, then install the beams. If the ground drains well and stays frost free all year round, you will not need to make the gravel drainage bed. If you don't have good drainage you will need to do this and I will explain how later in this article.

To start, you need to lay out the shed, which you have already done, then remove the sod and 3 to 4 inches of soil from the site. Use your batterboards and level mason's line put masking tape or some kind of mark every 4 feet to help lay out where your piers will go. Run mason's lines across the taped points. Square the lines by applying the 3-4-5 triangle rule which you can find in my "how to lay out a deck" article. With a plumb bob and powdered chalk, mark the locations of piers on the ground where the lines intersect.

The next step is to dig your holes for the footings. These need to be 12 to 14 inches square and 10 inches below the frost line. Shovel 4 inches or so of gravel into the holes for drainage and tamp it down with a 2x4 or something similar. Build square forms or of 1x6 material for the top of the footings. Seat the forms over the holes and level the forms on all sides and with each other. If necessary, drive in stakes to hold the forms in place. Mix up your concrete and shovel it into the forms and holes. Work the shovel up and down in the concrete to help eliminate air pockets. With a straight edge scrape the concrete even with the top of the form.

Next it is time to install the precast piers on the footings, you need to do this before the concrete dries. Align the piers by placing a straight board across them with the board lying horizontally. Put the straight board on edge next and sit a level on top to level the anchors from end to end. You should let the concrete set for at least 24 hours before removing the forms. If necessary, place landscape fabric and gravel for drainage, if you already have good drainage you shouldn't have to worry about this step. Place 4x6 beams into the anchors on the piers. Level the beams from end to end, side to side, and with each other by slipping shims under them if needed. Next you simply nail the anchors to the beams.

You now have your precast pier foundation ready for the shed. This is a good way to do a shed foundation; it's very stable and will work in most applications. I will also go into how to do a concrete foundation in my next article. You are now ready to continue on with your shed.