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A lesson on building a curved stairway.

tony_soprano's picture

I'm posting this thread to generate some discussion on building a curved stairway and railing. With all the complexities and craftmanship that goes into the fussing and fitting that a lot of us are not familiar with, hopefully we can get some solid advice and pictures to go along with our chat session. I should point out that I'm on the learning end so only questions and thoughts from me.



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I work for a stair company, and would think it would be very hard to build one by following directions over the internet, not impossible, just very difficult. Try going to a job with someone building one and watching. I can think of a lot of tricks to make things easier, but would be hard (for me) to explain in print. Alot of people here have much experience doing stairs/railings, and I'm quite sure that they (and myself) can answer specific questions reguarding a particular problem, but to explain in general how curved (or somtimes straight) rails and cases are built are the things entire books are written about.

(post #162882, reply #3 of 133)

Tony: Chris is right. Curved stairways are hard to explain. However, if you have a specific stairway that you could give us the floor to floor height, foyer size, etc., there would be several including myself that could take you through the layout procedure.

From there, I would give my methods for actually building this stairway. Everyone has different methods, but in the end, what is important is that we all end up with a nice stairway.

I would be more than happy to make some drawings, post some figures showing how you arrive at a stairway that has a comfortable walking line, meets code, etc.

Curved stairways are complex, but can be broken down into a bunch of simple steps, no pun, Ha.

(post #162882, reply #4 of 133)

Tony: If say you do not have a particular stairway you need figured out, I could post one of several that are stored in my computer that have been built, or are being built.

I have many pictures that I could post that should be able to help you see that you can build complex curved stairways with a minimal amount of equipment.

In my case, I have a small stairshop, with just my wife as a part time worker. My equipment consists of a cheap table saw, 8 inch jointer which I just upgraded from a 6 inch one, thickness planer, a good router with lots of bits, the rest is just simple jigs and hand tools.

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Stan, How 'ya been?, somehow I knew you'd find this one. Figure how to cable a curve yet?

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Chris: How is it going? I am still going in circles, myself. I never got the cable idea to help much yet. I will pursue it big time on my next freestander.

I don't do many of them, its just I am always experimenting.

(post #162882, reply #6 of 133)

For starters I would like to emphasize building staircases is like skinning a cat, namely there is more than one way to do it. Most of us who do it full time for a living have developed our own methods to make the job go easier (for us). I for one would like to see how other people go about it and learn something new in the process.

(post #162882, reply #7 of 133)

Armin Hammer: I agree. However, I get a lot of closed minded visitors to my shop that come from some of the nationwide stairbuilding firms out of Chicago. They do not think like you or I.

They are out of the shops that have millions of dollars of equipment and over a hundred employees. They just don't get how I build curved stairways with such little equipment. They don't realize that a lot of us had to train ourselves, buy our own equipment, and also pay the bills. I love to visit their huge shops that kick out 12-1500 stairs a year, but I only do 12 to 15. However, when they start mocking my little shop, I quickly let them know that it is paid for, my wife does not have to work at all, and my biggest problem is the taxes I must pay for being successful at it.

Sorry about that, I will step down from my soap box.

Anyway, like you said, there is more than one way to skin a cat. I need to ask you more questions, and I will be soon, cause you look like you can really skin cats quite well.

(post #162882, reply #8 of 133)


Maybe you could start by explaining how you approach a job like the one with the Enkeboll balusters or the hickory unit. After you get your floor to floor numbers how much of an opening space do you need, to have a smooth flowing curve?

Once you have all the numbers above, how do you start laying out your assembly? What determines the radius of the curve? How are the stringers made?



(post #162882, reply #9 of 133)

Tony: It will take a lot of posts to handle this. Lets start off with a basic stairway. Do you understand laying out a straight stairway? If you have a little trouble with a straight one, we should discuss their layout first.

(post #162882, reply #10 of 133)

Tony: They say a picture is worth a thousand words, so I will post a few here. These are pictures of curved stairways being built in my shop. If you notice on the floor the poster board? I have drawn the inside and outside radii for the stairs I am building. The risers are also plotted on the arcs. Basically it is just a full size plan than I build vertically from. The 2 x 4 forms are projected vertically from the stringer lines. Each riser face is plotted equal distance along the arcs I have drawn. I use the forms to laminate my stringer material to. These laminates follow a constant rise from each riser face point, thus making a nice helical path. This path this stringer takes would be nothing but a straight line if this stringer were flattened out. So basically, if you follow a straight stair layout, then you are ready for going in circles.

Imagine the layout out of a straight stairway along a wall as a big right triangle. The horizontal side is the run of the stairs, the verticle leg is the rise, and the sloped side is the pitch of the stairs. Now imagine this triangle drawn on a big sheet of paper. A curved stairways outside stringer is nothing more than this triangle being wrapped aroung a vertical cylinder.

You have a constant rise/run elationship as the straight stairs has, its just also turning at a set radius.

There of course are a few formulaes you need to apply to figure these out, but as we get into this slowly, I am sure others will chime in.

I will post a few pictures of these forms and you can study them to think of some questions to ask. This is a very typing intensive topic as there are a lot of variables in laying out a stairway.

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Another shot of same stairs

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A third shot

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Heres a jump to present time. Obviously we skipped some steps, no pun, but the stairs on the right is the almost finished stairs. It is all in hickory.

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Heres another view of the almost finished hickory stairs. There is no scotia trim on as yet, as I am getting ready to clamp my rail bending forms to the tread nosings.

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Tony: This particular stairway that I just posted several pictures of, turns 170 degrees, has a floor to floor height of 132 inches. It has 17 treads/18 risers. Each tread turns exactly 10 degrees. The outside stringer has a wall face radius of 96 inches. The inside wall radius is 46 inches. I would be more than happy to run the figures for you to show that this is a comfortable stairway. I can also show you stairs I have been forced to build that I thought were less than comfortable. I try and stay away from them and let someone else build them.

I have noticed that a lot of homes are designed first, then the stairs are made to fit the available space. The most desirable way is to design the stairway first, having comfortable parameters, and then build the house around it.

I am amazed at ARCHITECT designed homes that have stairways that looked like a high school freshmen class designed the stairs.

(post #162882, reply #16 of 133)


Judging by times on your posts it seems like you get less sleep than I do. I attend college at night and have been busy writing literature papers, not my major by the way, (your never too old to learn something new!) So my participation will be sporadic, sometimes during the day but mostly later at night.

Anyways this is turning out to be a excellent learning post with yours, and hopefully others, extensive efforts. And you back up your words with pictures which allow us to analyze your work. (I also have to mention Pro-Dek for his contributions in outdoor work as well)

By the way I do understand a stair layout. Not yet on a curved one. Do you use a center stringer for support? How do you determine the wall radii? What is the width of the stair? How do you attach the stringers to the walls to make their removal easy for disassembling? In the second pic the inside stringer has a horizontal cut while the outside stringer has a vertical plumb cut, any reason?



(post #162882, reply #17 of 133)

Tony: That vertical cut on the outside stringer is the finish cut for it. The horizontal cut on the inside stringer is just my stringer laminates running wild. They will get cut vertically right behind the first riser.

I do not use a center stringer at all. I pocket screw and glue the top of the risers to the bottom of the treads. It makes an i-beam effect out of it. This is far stronger than nailing through the treads. I also screw and glue the bottom of the risers to the back of the treads.

The wall radii is determined by measuring from the top landing header to the wall that the circle will be tangent to. I then set the spring line of the stairs about 1.25 inches in front of the header. This gives 1/2 inch behind the top riser for wiggle room when installing. The spring line is the face of the top riser projected to the center of the stringer radius.

In the case of this hickory stair, the outside wall radius is 96 in, the stairs is 49.75 inches wide to the inside stringer face. If you want, I can go through the walking line calculations. This assures a comfortable and legal stairway. I am going to have to go right now, but I will post much more, I promise.

Attached is a picture of the inside stringer on my workbench. Notice the pocket screws on each tread cutout. I use 2-3 hundred screws each stairway.

This stringer has a solid hickory face laminate. The stringer consists of 4 layers of 1/4 inch luan, along with a 5/16 face laminate. Solid strips of hickory cap off the laminates making it look like it is all solid hickory throughout.

The outside stringer is just temporaily screwed to the bending forms. When I am ready to move it, the stairs is just left standing on props. Then I get about 8 guys to load it on a trailor. I move the whole stairway right through the front door ,and set it in place. The outside stringer is lagged to each stud inside the stairway with 3/8 x 4 inch lag bolts.

(post #162882, reply #18 of 133)

Tony: Here is an outsidecurved stringer that shows how I have mortised for the treads and risers. I use oak wedges from inside to drive the treads and risers up tight into their mortises. It is a very strong, and time proven method.

I use a template that guides my router to do this. There have been several articles in FH about this detail.

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This is an elliptical stair on moving day. I took a vertical shot of it showing how each tread is a different pattern.

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Tony: Here is another stair that I installed a few months ago. Again, these are the stringers being worked on on the forms. You can see the outside stringer already routed.

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Same stair with the treads and risers in, and the handrail being glued up on the treads.

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Tony: Here is this same stairway installed with a view down the railing before the balusters were put in.

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Tony: Here is another view of the hickory inside stringer. It goes in the stair to the right in the background.

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Tony: Heres a stairway after the forms have been stripped away. This is ready to load.

(post #162882, reply #25 of 133)

Hey Stan,

I admire your contibrutions to alias tony's education.

But your first few post, as well as the others, are correct.

This is just too much to try to explain in words. However, you're doing a fine job of it.

You should write a book.

Those of us, like you, who do this for a living know that this is a subject not for the beginner or the faint of heart. It can take many trial and error efforts to refine a method that works for the individual. I always build them in place. You, and others, build them in the shop. That idea scares me to death.

One mans meat is another mans poison.

I'm enjoying your post and pictures.



(post #162882, reply #26 of 133)


A few questions. How much does the typical stair shown weigh? How long does it take to build one? How fast could you do it if rushed? How much extra would that cost? Do you cut the open stringer with your router? Wanna give a 'plug' to your router? How do you actually mark the stringers? A jig? Ever seriously damage one in transit? What is the farthest you've ever shipped one? Do you insist on installing them yourself? Thanks
Rick Louquet

(post #162882, reply #27 of 133)

Ed: Thanks for the comments;

Now for me, I love doing as much in my shop as possible. I do not like working in the field near as much.

I have a system that works for me. So far I have never had to trim the wall stringer. I have always supplied the curved wall plates, and also marked exactly where they go according to my springlines. It would be a nightmare if my stairs did not fit!

That hickory one I have in the shop is going to be the largest I have ever moved.

The largest stairway I have ever built, I installed early this year. I had to build it in my shop. disassemble it then reinstall it. It was a freestanding stairway with a 153 inch floor to floor height. I will post several pictures right now of it.

Thanks again Ed.

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Anothe shop view

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some finished shots;; pardon the clutter

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Your work is beautiful! I think Ed is right on... write a book if ya do I'll put in an order for my copy right now. Tauton Press will help you with this I believe, at least a few articles in FHB. You have alot you can teach the rest of us. I can build simple stairs but the curved stairway adds so much! Wish I could watch you work for a few weeks, I'm sure I'd learn volumes.