A pole-barn foundation is built with several square posts or round poles that are dug down to the frost line. The posts support the walls, so the floor can be made of wood, poured concrete, brick pavers, or even just gravel. Pole-barn foundations are ideal for large structures, especially if you’re storing heavy equipment, such as tractors, boats, and trucks.
Step 1: Prepare the Site
As with the other foundation types, when you build a pole-barn foundation, you will need to clear the area of any obstructions. Pull out shrubs, rocks, and trees, and level the ground. A skid-steer loader or backhoe makes site prep much easier. If the site gets soggy from time to time, put down 4 to 6 inches of gravel to deter erosion. And when preparing the site, clear an extra 5 feet of workspace around the area.
Step 2: Layout Out the Post Holes
Use pine 1x4s to make several batter boards. Each batter board consists of two wooden stakes and a horizontal string board. Install two batter boards, set perpendicular to each other, at each corner of the foundation. Then install two more batter boards across the center of the foundation. Stretch strings across the batter boards, securing the ends of the strings to the horizontal string boards. Now, adjust the strings until they form perfectly square corners. Measure diagonally across the opposing corner. When the two dimensions are the same, the strings are square.
Step 3: Dig the holes
Dig the post holes down to the frost line using a manual post-hole digger or gas-powered auger. If you live in a warm region with a very shallow frostline depth, dig the holes at least 24 inches deep.
Step 4: Set the Posts
Line the bottom of each post hole with 4 inches of gravel. Compact the gravel with a long 4×4. Next, stand the posts in the holes and hold each one plumb with two diagonal braces cut from 2x4s. Screw the upper ends of the braces to the posts, and screw the lower ends of the braces to 1×4 stakes driven into the ground.
Step 5: Pour the Concrete
Mix the concrete in the proper proportions and pour it around the posts to completely fill each hole. Smooth the top surface of the concrete with a margin trowel, sloping it slightly away from the post to drain away water.
A pole-barn foundation is super-strong, quick to build, and, when dug down to the frost line, serves as a permanent foundation. Once it is done, you will be ready to start building the rest of your shed. For detailed information on flooring framing, click here.
Joseph Truini is a host on the Today’s Homeowner TV show and co-hosts the weekly Today’s Homeowner Radio Show. He has written three best-selling shed-building books and lives in Roxbury, Connecticut.