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I am figuring on an elliptical stairway. The first post will show a foyer that is wide but shallow, one that a circular stairway will not work in, but possibly a good candidate for an elliptical. The drawing shows the foyer with the existing top header and sidewalls already in place. The following posts will show what I have to consider in determining whether this is a comfortable stairway.
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The width for the stairway is 154 inches from face of top riser to the sidewall. The depth of the stairway from the bottom riser face to the back wall is 112 inches. The width of the stairs is 48 inches.
The floor to floor height is 119 inches. I am using 15 treads and this makes each of the 16 risers 7.4375 inches.
I have to figure what the walking line run is to see if this stairs will be code acceptable and comfortable.
I figure the walking line as an imaginary line 15 inches from the handrail centerline. This is the path that an average human follows as they are ascending/descending a stairway.
Referring to the drawing, I am figuring an elliptical path with a semi-minor axis of 79 inches and a semi-major axis of 121 inches. Using the approximate formulae for the perimeter length of an ellipse as found on the drawing, the math works out as follows in the next post..........
*3.14159 x sq. root of [ 2{79squared + 121squared}]3.14159 x sq. root of [ 2{ 6241 + 14641}]3.14159 x sq. root of [ 2{20882}]3.14159 x sq. root of [ 41764]3.14159 x 204.362= 642.023 inches....this is the whole perimeter .....so we take one fourth of thiswalking line run length = 160.505 inchesdivide this by 15 and I come up with a run of 10.7 inches........very comfortable.
*Quick question Stan. You say that a circular won't work. Would it be more correct to say that a circular would not be aesthetically pleasing, but could technically work, using that same run?blue
*WOW!
*Blue;; the depth would determine the max radius of a circular. This is only 112 inches. If you figure the walking line run for a 79 inch radius circle, it is only 124.09 inches for a quarter turn stair. This divided by 15 treads leaves only 8.27 inches of run. Thats where I determined a circular would not work given the parameters of the foyer.
*Stan, you just threw in another variable: it is a quarter turn stair.I was thinking that a circular stair was possible, but would extend beyond a quarter circle, thus disrupting the aesthetics of the project.Ok, now I'm on the same page.blue
*Blue: I failed to mention that. The right side in that drawing I posted has a cased opening to another room. I have it drawn that way, but didnt clarify it. If the option was available to swing the stairs past 90 degrees, then the run may have worked.
*Way over my head Stan-the only roots I know about are the tree roots I have to cut before pouring footings, and they're not square, they're usually round. :-)
*Bob: pie are not square---pie are round---I have eaten to many of them to know
*Stan, you are truly amazing, what wood species? A quick question, the 15 inches railing centerline to walking line is that your determination or is it code in your area? My trade books call for 13 inches which is what I have always used however code up here is 12 inches from the centerline.
*Armin: From what I have seen of your work, you are the amazing one! This stairway will probably be all oak.The 15 inch is what I have based my figures on for years. I measured in from a rail centerline and 15 inches is what my average distance from the handrail is as I am ascending and descending a stairway. I have seen this figure published in books ranging from 12 inches to 18 inches. I guess its all relative. The larger the distance from the rail that is used, the greater should the run be, of course. I am sure that I use a slightly longer run at my distance of 15 inches than you do at 13 inches. We both end up doing the exact same thing only just calling it different.Example: typical stairway... handrail centerline radius of 90 inches with my 15 inch walking line. There are to be 15 treads in this 90 degeee stairway. The radius of this walking line is then 105 inches. This makes a circumference of 659.73 inches. Divide this by 60 and that is the walking line length of this tread of 10.995 inches.Armin, then if we use your 13 inch walking line, that gives your walking line radius 103 inches, and a circumference of 647.168 inches. Dividing this by 60 gives your walking line run 10.78 inches.So its really relative. I will tend to use a larger figure with my walking line run than you will with your 13 inch run. In this case the difference is less than a quarter inch.I feel a walking line run near 11 inches is great figured at 15 inches from the centerline. I try to stay closer to 11 than 10 inches which is my personal minimum. Using your 13 inch standard, then if you use a 10.75 inch figure, we are both doing the same thing. Or going to the 12 inch, it would be just a tad less of course.
*Stan, I knew it was just spliting hairs more or less just curious, actually worried if I had been screwing up all these years and didn't know it.
*Armin: Believe me, if you said you had to have 11 inch run at a 13 inch walking line, I would not question it, and would automatically adjust my run at 15 inches to be a little larger. By the way, what do you consider your minimum run at a 13 inch walking line?
*Stan,i By the way, what do you consider your minimum run at a 13 inch walking line? 9 1/2 inches is rock bottom minim. In a few cases, do to the usual not enough room to do it right, I have had to drop to 9 inches. My ideal is 10 inches plus the nosing. Do you ever run into the following: In 50% of the cases the designer, builder or architect does not allow enough room to properly build a staircase. It seems they design a house and the stairs are an afterthought. A summer home we worked on several years back was designed by a major firm out of Chicago, $450,000 worth of "Our Camp". The plans called for a L shaped two flight, landing half way up staircase. If I would have built it without checking the site I would have had 36 inches of headroom at the landing. In the end the only thing I could do was build a tight winder, spiral, seat of the pants combo. Ironically this house was featured in Architectural Digest and the only reference to me was the mill work and stairs were built by "The eccentric woodworker from Munising". Imagine that, ha!
*so, armin.. u mean you're not "The eccentric woodworker from Munising".?did you notice it was published in Architectural Digest ?.. not Builder's Digest... p'haps they were writin to a different audience... nu?. i was just reading a note in our Chief Architect user group.. seems that if you spec the walking line.. when the program draws the curved stair .. everything will conform to that walking line.. i haven't used it yet.. just straight stairs.. still.. kinda neat that it would do that..
*Mike,i so, armin.. u mean you're not "The eccentric woodworker from Munising".? Slightly out of round yes, eccentric no. Architectural Digest June 2000. It was one of these rare cases, right from the getgo, the architect and I clashed about the merits of custom woodwork. She could not see how anyone living under a stump, so to speak, was qualified to build anything of hers. The client took her on a tour of several of my past projects and insisted she use my stuff. In the end I came in under budget and ahead of time but I cut into her design dramatically, the client loved it but I ended up eccentric. The photo is a curved section of rail, main floor, the space is so tight I couldn't get a decent shot of the actual stairs.
*Armin: I liked your 9.5 inch minimum answer. We are on the same page. I would also say that about half the time there is not enough room for a proper run. It seems they design the house first, then I get left with the remaining space for the stairs. So then one has to get out his bag of stair tricks and add a winder, chop back a header, take out a tread at the price of increasing the rise, etc. Now at least with several of my contractors, I will sit down and design the stairway first, then they design the house around it. This saves a lot of compromising and gives the client a better stairs.
*armin.... now that's a nice piece of work fer a rustic like u.... course it's not fair.. orlo can't respond to your drops and tell you how it should have been done...did i tell you i almost bought an accumark.. nice lookin layout tool... but since i do about one curved stair rail every ten years or so.. it was a little more than i needed to spend
*Armin: That railing was sharp. Nice work!
*Is that the same railing that is in the other post with the bald spo..Oops. That is a nice looking job,fer a stump dweller.
*Armin, Nice details, care and thought is very evident.You humble us with your presence.
*Phil, Presents? I didn't know I gave you guys any presents!