Building a wooden staircase is a complicated project, best left to very experienced woodworkers. If you're ready to tackle this project, be sure you understand how to take accurate measurements and make accurate calculations. They are the first and most important step in building a safe wooden staircase.
Step 1 - Do the Prep Work
Check your local building codes. They will give you important measurements that you must follow, like minimum tread size and maximum riser height. Determine how much headroom you need and calculate things like the number of treads and the total staircase run length.
Measure from the floor to the second level, divide that number by 7.5, then round up for the number of risers you'll need. Subtract 1, and you have the number of treads. For the total staircase run, multiply the number of treads by 10 (if they're 10-inches). Then add the width of the top riser and the amount of the nosing of the bottom step, which is the measurement of how far the tread extends over the riser. That figure is the total staircase run.
Step 2 - Make Final Calculations
Now calculate the thickness of the upper floor-joists, the drywall and actual upper-level floor. Add this amount to the amount of headroom you want. Divide the total by the riser height. This is the number of treads you will need in the clear opening to achieve the right amount of headroom. Multiply this number by 10 and add the top riser thickness and bottom step nosing. The result is the length of the staircase you'll need to get the proper amount of headroom.
Step 3 - Create Stringers
Adjust the framing square clamps on the board you'll use to make a stringer to 7.5x10-inches. Mark the number of risers and treads that you need, starting with the bottom riser. Draw in the line for the second floor. Double-check before you begin cutting to make sure you have the proper amount of risers. Repeat for the other 2 stringers.
Step 4 - Make Stringer Adjustments
You may need to adjust the top and bottom risers according to the tread thickness. After adjusting, calculate whether the bottom or top risers are too high. This can happen when you add a tread that is 1-inch thick.
If the risers are too high, remove 1-inch from the bottom at floor level to compensate. Use a power saw to cut the triangular portions. Don't go beyond the lines and cut too deeply as this can weaken your staircase foundation. Put your 3 stringers together to make sure they match perfectly.
Step 5 - Install Stringers
Position the left and right stringer on top of your skirt boards and cut out the proper notch, then attach the boards. Install the stringers using screws into studs for safety.
Step 6 - Risers and Treads
Rip the risers to the correct heights. Put them in place with either nails and glue or screws and glue. Cut tread boards to length and screw them into place. To complete your wooden staircase, mount the proper handrail along the wall or walls according to your local building codes.