![]() ![]() ![]() Its r+R is 18” and its 2r+R is 25”, right where they should be. ![]() I call it a lazy stair, because it seems to take no effort to use (but you still feel like you’re getting somewhere). I usually end up having to squeeze the stair for one reason or another, but on the rare occasions I can include a 7-11 stair, it ends up being very comfortable. My ideal stair has a 7” rise and an 11” run. If it meets neither number, it will not be comfortable. If it meets only one of the numbers, it will be less comfortable. If a stair meets both numbers, it will be comfortable. After trying to decide which rule really was better, I settled on the idea of using both. I relied on the 18” rule for several years, until I met another carpenter who insisted that a better measure was that twice the rise plus ( 2r+R) the run should be 25 inches. The IRC limit gives an r+R of 17 ¾”-pretty darn close to 18. On my first stair, r+R was roughly 15 inches-way too far from 18” to be comfortable or safe. You can cheat a bit up or down, but below 17” and more than 19” will result in steps that require strides either too big or too small for most people. Why? That’s what most people find to be a comfortable stride on most stairs. Rule one says that rise plus run ( r+R) should equal 18 inches. They use the term “tread” instead of “run” but I think that’s the cause of some confusion, so I’ll use the standard term “run.” IRC code limit stair: The IRC ( International Residential Code) calls for a maximum rise (“ r”) of 7 ¾” and a minimum run (“ R”) of at least 10”. It’s the horizontal distance from the face of one riser to the face of the next riser, or from nosing to nosing, and the other stringer cut-it’s NOT the size of the tread itself, which includes a leading edge overhang of ¾” to 1 ¼” (according to the IRC for most residential stairs). The “Run,” however, seems to cause some confusion. It also happens to be the dimension of one of the cuts on each of the actual stair stringers–the framing members that hold up the stair treads. Since then, I’ve built and/or designed many stairs, and every time I think about the lessons I learned on that first one.įor anyone not familiar with the terms, “Rise” refers to the vertical distance from the top of one tread to the top of the next tread. Although the rise itself wasn’t terrible, something about using it felt very cramped, and I set out to find what went into a safe, comfortable stair. The result was a disastrously uncomfortable stair, with treads too short for adult feet. Elevation grade also helps when examining the flow of water from higher elevations to see if the land can be irrigated without pumps.On the first stairs I built, I sized them for a 1×8 riser and a 2×8 tread.Building structures on a sloping area may require some additional foundation to avoid failing. Knowing the terrain's angle of elevation also helps when assessing a land's ability to support a structure.If you wish to learn more about retaining walls, retaining walls check out our retaining wall calculator. Therefore a retaining wall can be constructed against a cliff to avoid landslides. Retaining walls support the earth above it to keep it from eroding downhill. Determining the elevation grade also helps when building retaining walls.Cutting-and-filling is where soil from the higher part of the slope is transferred to the lower part to reduce its grade. Engineers can design a cutting-and-filling procedure for less steep terrain to decrease the slope. Very steep terrain may require roads to be laid out in a zig-zag pattern for safer ascending and descending. We use it, for example, in the vertical curve formula. Knowing the area's elevation grade helps in the construction of roads.Here are some examples of the importance and advantages of knowing the grade of a particular area: It may also be a requirement to proceed with other activities, such as construction or irrigation. Knowing an area's elevation grade offers many advantages over not knowing it at all. ![]()
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