By applying the principles of a wilderness lean-to structure to a pole barn, you can build one of the simplest outbuildings in any size. Build the barn with the poles on one side taller than the poles on the other with a flat roof and you have a lean-to pole barn.
Draw out the plans for your lean-to pole barn before building so you know what size lumber to buy and how large an area to clear.
Decide which side of the barn to leave open. Traditional lean-to structures have one to three sides closed and one open.
Build the lean-to pole barn in the right location on the property, with the open side facing the prevailing direction of the travelling wind. This prevents wind, snow, dust and debris from blowing directly into the open barn structure.
Prepare the floor of the barn. Set the poles into the ground below the frost line before laying any gravel or concrete for the barn floor. Put the two taller posts on the side facing away from the wind and the two smaller posts on the side facing into the wind.
Connect the four or more posts using the right length 2 by 4s, nailed in place about 12 inches above the ground and again 12 inches below the lowest roof line. The boards connect three sides of the pole barn with one side open. Place more 2 by 4s between, about every 12 inches, as nailers.
Build the roof by nailing 2 by 6s along the top of the same-size poles to form the top of the outside wall. Do the same along the top of the poles on the other outside wall. These boards are laying parallel to each other. The roof slopes away from the wind.
Lay 2 by 6 boards, slightly longer than the width of the roof, across the two boards on the poles and nail in place. Place the 2 by 6s about 18 inches apart.
Parallel to the first two roof nailers laid at the top, lay additional roofing nailers the length of the roof if needed, spacing them every 4 feet.
Use plywood, tarpaper and shingles for a traditional style roof on the lean-to roof of the pole barn or lay metal roofing on top of the nailers.
Put up barn siding on three sides of the pole barn, nailing to the 2 by 4s.
Add a sliding barn door to the open side of the lean-to structure if wanting an enclosed structure.
Consider adding a lean-to pole barn structure to an existing barn and treat the barn as the open side of the lean-to when building.
Measure twice and cut once. Start with a smaller pole barn structure first before attempting a major project.