How to Calculate the Floor Space Needed to Install a Stairway


You just need to have a fundamental understanding of mathematics in order to calculate the space that your steps will take up. If your middle schooler is in need of further math work, you should ask him to conduct the calculations for you. Stairs and stairwells are subject to very stringent building code rules in the state of California. This provides you with a precise set of values that can be plugged into a simple calculation in order to determine the required quantity of steps as well as the amount of space required to construct them.

  1. Take a measurement of the vertical distance between the floor at the position of the bottom of the stair and the floor at the location of the top of the stair. This is the total elevation gain caused by climbing the steps. Don’t go by the height that you already know the room to be. There is a possibility that the height varies slightly, or that there are tolerances for floor joists that were not included in the measurement.

  2. Take the entire increase and divide it by the predicted height of a unit climb. The unit rise height refers to the desired overall height of the steps. According to the California Building Code of 2010, the height must be anywhere between 4 and 8 inches. If the answer to your equation is a fraction or a number that is not a whole, such as 12 and a half, then round it up to the closest whole integer. In this scenario, it would equal the number 13. The sum of these digits is the entire quantity of risers.

  3. Take the total number of risers and divide it by the overall climb. The riser height will be determined precisely based on this.

  4. Simply multiply the total number of risers by the width of the treads you have already chosen. It is against the law for treads to be any narrower than 9 inches in the state of California. The overall run length of the stairs will be equal to the sum of the numbers that you finally equalise.

  5. Determine whether or not there will be stairs positioned beneath the second level by checking the total run length of the building. The California Building Code of 2010 mandates that there must be a clearance of at least 80 inches between the top of an individual step and the bottom of the floor below it. Modify the width of your stair tread and the height of your risers until you come up with a formula that offers that much space. If 80 inches is not available, adjust the width of your stair tread and the height of your risers. This change will have an effect on the incline, also known as the steepness, of the steps.

  6. Take a measurement of the handrail’s breadth. It is required that there be at least 36 inches of space between the handrail and the opposite end of the stair tread, and that the handrail cannot overhang the tread by more than 3 and a half inches. To calculate how broad the stair area has to be, add the length of the railing to the length of each step. If the handrail is wide. If the drywall has not been installed on the wall at the steps yet, you will need an additional half an inch of space in the overall area that is required for the stairs.


    Make sure the calculations are correct according to the International Building Code by checking them. To calculate the riser width, multiply the precise riser height by two and add one tread’s width. This value must be between 24 and 25 in order to be in compliance with the code. While the state of California does not mandate that you do this, doing so will guarantee that you have the safest stairs possible.