How to Build Stairs That’ll Step Up Your Home’s Style

Calculate the Rise of the Stairs

Before you can learn how to build stairs, you’ll need to establish the overall height of the staircase. 

1. For an indoor staircase, you’re likely working with a level floor. Simply measure the distance from the upper finished floor height to the landing or floor below to determine the total rise of the staircase. 

2. For an outdoor staircase where the ground is uneven, determine the distance that the stairs will reach out or, in other words, its total run. 

3. Find the distance by leaning a straight board from the top of the stair header to the ground at a 32-degree angle. 

4. Determine the angle using an angle gauge tool. Mark the end location on the ground.

5. Have an assistant extend a long, straight board out from the top of the stair header to the mark on the ground. Level the board with a bubble level.

6. Measure the vertical distance from the bottom of the board to the ground. That number will be the total rise of the outdoor staircase. 

Determine the Number of Risers and Treads Needed

Standard building codes govern stair measurements. The minimum and maximum rise of individual stairs must be between 4 and 7-3/4 inches. 

1. A typical stair riser is around 7-1/4 inches tall. First, divide the total rise by 7 inches to achieve a height near that number. 

2. For example, if your total rise is 9 feet, divide 108 inches by 7 to reach 15.43 inches. Round down to 15, which will be the total number of risers in your staircase. 

3. If your top stair isn’t going to be level with the floor above, subtract one riser for a total of 14 risers with a total rise of 101 inches. 

4. To determine the number of treads, subtract one from the number of risers. Our example will equal 13 treads.

Calculate the Height of the Risers

Now for the more precise calculations for building a staircase.  

1. To find the precise height of each riser, divide the total rise of the stairs by the number of risers. 

2. In our example, divide 101 by 14 to equal 7.21 inches per riser. 

3. Save that number for later.

Calculate the Run of the Stairs and Stringer Length

The next crucial measurement for building steps is the length of the stringers. 

1. First, determine the depth of each stair tread. A good rule of thumb is to keep the sum of the run and rise of each stair near 18 inches. 

2. For our example, let’s choose 11 inches deep. The sum of 11 and 7.21 is 18.21 inches which is, as they say, close enough.  

3. Now multiply the depth of each stair tread (11) by the number of treads (13) to determine the total run of the staircase (143 inches).

4. To find the length of the stringers, multiply the total rise of the staircase, excluding the distance from the top tread to the upper finished floor height by itself (101 x 101 = 10,201).

5. Multiply the total run of the staircase by itself (143 x 143 = 20,449).

6. Add the two totals together and find the square root of the total to determine the total length of the stringers and skirt boards (175.07, or 14.6 feet). Now you know that you’ll need stringer lumber that’s at least that long.

Mark and Measure the Stairs on a Stringer

Photo: Jeffrey Banke / Adobe Stock

Use a 2-by-12 board longer than the total length of your stringers to make the first one. 

1. Affix the stair gauges to a carpenter’s square. Place one at the riser height and one at the stringer height on the other side of the square. 

2. In our example, mark 7.2, or just shy of 7 1/4  inches, and 11 inches on the other side.

3. Starting at the bottom of the stringer, clamp the carpenter’s square so that the corner is on the face of the board and the gauge’s stops are snug against its edge. 

4. Trace the triangular shape onto the board. Be aware of which side of the square represents the riser and which is the tread.   

5. Repeat the process until you have drawn your staircase's total number of stairs.

6. With the carpenter’s square or another straightedge, make a line horizontal to the bottom of the stringer that represents the thickness of your tread lumber. You’ll cut off this excess later. 

7. Make a cut line representing the excess material at the top of the stringer and square the board to the header lumber. 

Use a Circular Saw to Cut the Notches

Use a circular saw to perform the rough cuts and finish with a more precise saw. 

1. Cut the top and bottom excess material from your stringer with a circular saw.

2. Make cuts with a circular saw along your cut lines for each step. 

3. Stop cutting approximately 1/4 inch from the inside corner where the lines meet. 

4. Remove the triangular waste from the string by finishing each stair cut with a jigsaw or handsaw.

Test Fit the Stringer

Now is an excellent time to make sure everything is looking good. 

1. Set the cut stringer in place. 

2. Check the treads for level with a torpedo level.

Use the First Stringer to Outline the Next

When satisfied that the first stringer is correct, it becomes a template for the following pieces. 

1. Lay the cut stringer on another 2x12. 

2. Line the cut stringer’s long edge up with the other board’s edge and clamp it in place.

3. Trace the outline of the cut stringer onto the uncut board.

4. Repeat for all stringers in your staircase.

Mark and Cut Skirt Boards

Skirt boards affix to the outer edges of the staircase as decorative trim, for safety, or both.

1. Lay the cut stringer on another 2x12 and clamp it with the long edges aligned.

2. Trace the bottom and top cuts onto the board. Exclude tracing the individual steps. 

3. Cut the skirt board on the marks with a circular saw.  

Cut Remaining Stringers

Photo: Jeffrey Banke / Adobe Stock

Cut the remaining stringers following the traced lines from step eight. Remember to stop short of the inside corners and finish the cuts with a jigsaw or handsaw to avoid overcutting and weakening the stringers. 

Attach Skirt Boards and Stringers

Depending on your staircase, you can perform this step now or after you install the stringers. 

1. Align a cut skirt board to a cut stringer and clamp them together. Be sure to position the skirt board on the outside of the stringer. 

2. Affix the skirt board to the stringer using 2-inch screws. 

3. Repeat for the other side.

Make Sure Stairs Are Squared Off

For the most secure installation, use steel stair hangers to attach the staircase to the house structure. 

1. Add the height of one riser plus the thickness of one tread and make a mark on the header representing that total. 

2. Fasten the top of the stringers to the header board using staircase hangers and joist nails at your mark on the header.

3. After attaching the two outer stringers, square the staircase by matching the measurements between the opposite corners at the top and bottom of the stairs. 

4. Attach the bottom of the stringers with L-angle joist hanger brackets on the inside of the stringers.

Cut and Install the Stair Risers

Your staircase may still feel a little flimsy. Installing the risers will fix that. 

1. Measure the width of the staircase between the skirt boards. 

2. Cut 1x8 lumber to that measurement until you have enough risers.

3. Use a table saw to rip the risers to the correct height if necessary.

4. Start at the bottom and install each riser with 2-inch screws. Use at least two screws per stringer. 

Cut and Install the Treads

Stair treads less than 11 inches deep will require at least a 3/4-inch nosing on each one.

1. Using the riser width measurement, mark and cut the treads to the correct width.

2. Use a table saw to rip the treads to the correct depth if necessary.

3. Start at the bottom of the staircase and install each tread by driving 3-inch screws through the tread and into each stringer.

Install a Staircase Handrail or Railing

Before calling the city to schedule your inspection, install a railing or handrail that meets building code requirements. That could be a whole project in itself. Call a local handrail installer if you'd like help with that part of your project.