When designing or building stairs, the most critical figure is the rise per step.
Most building code requirements set this number at ‘less than’ a certain amount and that amount is usually around 7 3/4 inches. Sometimes, it is over 8 inches, like 8 1/4 or 8 1/2, but sometimes it is under 8, like 7 3/4 or 7 1/2. For seniors or children this is a good number and this is what the requirement is designed for. For healthy strong adults a rise of 8 or more is fine, but staircases have to be designed for the lowest common denominator. Aging knees and small bodies prefer the mid-sevens.
Initial stair building calculations
To start with your stair building project, calculate the number of steps you need. Take the total rise and divide it by 7. If your total rise is 96 inches, divide it by 7. This gives 13.7. This number reflects the number of stairs at that rise.
Since you can’t have “.7″ steps or treads, you have to decide if you want to go up or down to 13 or 14 steps when building stairs. If you pick 14, your rise will be less, if you pick 13, your rise will be more.
Pick 13 (go down). 96 divided by 13 is 7.38, or about 7 and 3/8. This is a good rise for your stair building project, and will most likely fall into code requirements for your locale. Code is almost always satisfied by less than 7 1/2, and usually by 7 3/4. This is all calculated by several online stair building calculators. Some are free and some cost a few bucks. You get what you pay for. There is an excellent calculator for building stairs at www.Shalla.Net that works it all out for you. There are a few free calculators for building stairs that give you rise and run but don’t give you a step by step measurement process. Pick one, and mark your stringers.
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