The first thing you will need is a plan when building basement stairs. Follow these steps to complete the project.
Step 1 - Plan the Stairs
It is necessary to understand the meaning of the terms “rise” and “run” when determining the size of your stair treads and risers. Tie one of the nuts or bolts to the string and drop it from the opening above the basement to the floor below. Measure this distance to determine your rise. Mark the floor where the nut lands and then measure outward from there to the spot where the stairs will end. Doing so will give you your run.
To calculate the number of risers you will need, convert the rise to inches and divide by seven. The number of risers determines the number of steps needed in for stairs. Subtract 1 riser to determine the number of steps. Change your run measurement to inches and divide this number by the number of calculated steps to determine the width of your stair tread.
Step 2 - Lay Out the Stair Frame
Place the 2x12-inch stair stringer on your sawhorses. Using the square nuts and framing square, adjust the framing square and square nuts until you see your measurements for the rise and run at the end of the board.
Ensure that your rise and run numbers exactly at the end of the board. Lay the stairs making sure that every line touches the other. The first rise won’t be on the 2x12-inch board because it is the first step you take on the stairs.
¾-inch OSB is used for the first rise by nailing it to back of the 2x12-inch stringer. Use it to connect the stringer to the floor joist, which is part of the subfloor. Outline the rest of your stairs on the stringer using the rise and tread calculations you have determined. Cut-out the rise and tread of your steps on the stringer.
Step 3 - Building the Stairs
After you have cut the stringers to accommodate the treads, you are ready to assemble the stairs. Nail a riser at the top and at the bottom of the staircase. Nail the rest of the risers.
Once the stair stringers are installed, you can nail the treads onto the stair stringers. Nail the treads once the stair stringer is installed; otherwise, the stringer will be too heavy to lift and hold in place during installation.
It may seem like a lot to remember, but just follow the instructions and you will be surprised at how well this project turns out. You will also be very satisfied at having tackles this project yourself.