Step 1
Hold a stair stringer in place along the wall studs. Stair stringers vary in dimension to fit the space in which you’ll be building the staircase. This requires two people. One holds the top of the stringer flush with the top of the upper floor framing and the other positions the bottom of the stringer flat on the floor below.
Step 2
Make marks on the wall studs right below the bottom of the stringer. Mark more than one stud while holding the stringer in place.
Step 3
Cut a 2-by-4 to match the stringer dimensions. The easiest way to cut this board is to lay the stringer on the floor and hold a long 2-by-4 flush along the bottom edge of the stringer. Mark and cut the top and bottom of the 2-by-4 with a circular saw to match the angles of the stringer at the top and bottom.
Step 4
Position the cut 2-by-4 so the bottom of the board lines up with the guide marks you made on the wall studs. The top of the board should be flush with the top of the floor framing and the bottom of the board should rest evenly on the floor.
Step 5
Insert two framing nails, evenly spaced, through the 2-by-4 into every wall stud it crosses.
Step 6
Position the stair stringer so the bottom of the stringer is flush with the bottom of the installed 2-by-4.
Step 7
Nail the stringer to the 2-by-4 every 6 inches, from the bottom all the way to the top. Now, you’re ready to install the freestanding stringers.