How to Keep Porch Piers in Line

Make batter boards from scrap lengths of 1-inch-by 3-inch boards. Tack two construction stakes to the ends of each board so it will be slightly above ground even when stakes are pounded into place. Make sure the top of the batter boards will be the same height as the porch rim joist already attached to the house.

Use two batter boards, arranged at 90-degree angles, at each of the two outside corner posts. Attach mason’s string to one end of the rim joist and run a length straight out to the parallel batter board; tie the string securely around the board. Run another string from the other end of the rim joist to that parallel batter board. Run a third string between the two batter boards, crossing the other two strings.

Make sure the mason’s strings are perfectly square by adjusting them as needed – sliding the tied ends along the batter boards – until the two diagonal lengths are exactly the same. These imaginary diagonal lines extend from each end of the rim joist to the farthest outside corner. Measure their distance with a tape measure.

Locate the center of each corner pier at the exact place where two lines cross. To locate that exact spot, drop the plumb bob where the lines intersect so it barely touches the string. Mark that point on the ground with spray paint.

Follow the same basic process to line up all other concrete piers, using the original mason's string lines and creating new batter boards as needed. Measure suitable distances along the rim joist to site piers there and along the porch’s opposite end. Do the same along the porch’s short sides.