Many local governments list their building codes online. Note that “riser height” is defined as the height from the top of one tread to the top of the next. Stairs with more than 1 step will probably also be required to include a handrail on both sides of the stairs. Open stairs, and the deck they serve, rising over 30 inches may also need guards on any open sides above the point 30 inches high. [2] X Research source NFPA 101 (2015):7. 2. 2. 4.

Measure the approximate height of the stairway you will build and the maximum space you can use on the ground. Check the pre-cut stringers at the store and measure their height and length. If they are longer than you need, you can cut them to size. To cut a stringer to size, cut it so the bottom step is not as high as the others. It can be much less high.

The 40-degree slope should start the bottom of the support beam of the deck because this is where the stringers will be attached.

Write down the measurements so you can calculate the materials later.

For example, if your total rise was 60 inches (150 cm), then divide that number by 7 to get 8. 57. Round that number up to get 9, and use 9 steps. Write down this number to use in your calculations.

For example, if your total rise is 60 inches (150 cm) and your approximate number of steps is 9, divide 60 inches (150 cm) by 9 to get 6. 67 inches (16. 9 cm) per step.

The number of steps you calculated is the number of treads that you’ll need.

For example, if your tread is 10 inches (25 cm), square 10 by multiplying the number by itself, which gives you 100. If your rise is 7 inches (18 cm), square that number by multiplying it by itself to get 49. Add 100 to 49 to get 149, then find the square root of 149, which is 12. 206. Multiply that by the number of steps that you have to find the total length of your stringers.

Most building codes stipulate that the stair stringers can’t have notches (saw-toothed or stair-shaped cuts) that are deeper than half the width of the board, or the stringer will be too weak.

Draw all of your cuttings lines onto the wood first, then check and recheck your measurements before you make any cuts. [9] X Expert Source Walter BrantHandyman Expert Interview. 2 September 2020. The sawtooth or stair-shaped pattern should match the rise and tread measurements.

Be careful when operating a circular saw. Wear safety goggles to prevent sawdust from entering your eyes.

Take care not to cut past the guidelines you marked or it could weaken the stringers.

Use the first stringer you cut as a template for the next two. [13] X Expert Source Walter BrantHandyman Expert Interview. 2 September 2020. If you’re building the stairs on a surface that isn’t level, your stringers may all 3 need to be slightly different lengths. Start by cutting the shortest one, then make the other two slightly longer on the bottom. Avoid using shims to adjust the stringers—they could fall out. [14] X Expert Source Walter BrantHandyman Expert Interview. 2 September 2020. Measure, mark and cut with precision; the limit for differences between tread depths or riser heights is 3/16 per stair and 3/8 total for a flight of stairs. [15] X Research source e. g. , NFPA 101 (2015): 7. 2. 2. 3. 6 (except a bottom riser resting on a landing).

After you’ve attached the first stringer, connect the second stringer to the deck by following the same process. Use 6 in (15 cm)-long corner braces on the two inside corners—look for the ones labeled “braces for stringers,” as they’re heavier steel than most braces. For extra strength, screw several 3 1⁄2 in (8. 9 cm) framing and decking screws diagonally through the stinger into the deck. [17] X Expert Source Walter BrantHandyman Expert Interview. 2 September 2020.

Use the first riser that you cut to make your guidelines on the rest of the boards so you have a uniform length.

Use at least 2 deck screws to firmly secure the riser to the stringer. Don’t drill too far into the wood or it could crack.

Use at least 2 deck screws to attach the tread boards.