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.

Stair building layout done – moving on to stair building

After you layout your stair stringers (or stair jacks, as they are also called) you’ll need to decide how to attach your stair stringers to the top level. You can simply extend your top level face down with heavy plywood, or you can use stair stringer hangers. Posts are another alternative. Posts all the way to the ground are very strong, but don’t always ‘fit’ a design. You need to make sure the staircase won’t collapse after ten years. Stringer hangers are a great way to go in your stair building project.

Stair Treads

Next in the stair building process are your treads. Treads are nailed onto the stringers. Make sure you have some overhang. If your run is 130 inches, and you have 13 steps, you have a run of 10 inches. Local code often specifies 10 inches minimum for run, so this would be okay. If your run is less, you may not have a code-happy situation. If you can extend you staircase to a point that satisfies code, great. Doing this manually takes a huge amount of time every time you change a setting. The spreadsheet at www.Shalla.Net calculates it all for you, but it’s 20 bucks. Anyway, find a calculator for building stairs that you are happy with, and let it do all the calculations. You need to have at least an inch of overhang for the treads.

Building stairs – final stages

stair stringer design calculatorYou’ve cut your stair stringers and your treads, and you have a staircase plan.
You need to put it all together. For basement stairs it doesn’t matter much, but if you want it to not squeak, you need to glue before you screw. Outside, for wooden deck exterior stairs, this doesn’t matter much, but for interior stairs, glue and screw. You may be well served to create an extra stair stringer. Code may require two stair stringers, but for nice firm stairs you need to exceed code requirements and go with an extra stair stringer. Code requires a minimum, to impress your users, you have to exceed code. Code is only for basic safety but consider it in your stair building project.

Posted by StairMan 2007-01-13 on HomeImprovementAndyBlog. We need your input for future projects. Good luck, Andy.

[tags]building stairs, stair stringer calculator, stair building, stair treads, rise run, stair stringer spreadsheet[/tags]

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