Spiral Staircase With a TON of Curves




Introduction: Spiral Staircase With a TON of Curves

About: A full-time maker with a strong interest in creating functional art with CAD and CNC, 3D printing, and traditional fabrication techniques. My specialty is spiral staircases and other architectural sculpture...

This instructable shows how we built a spiral staircase using CAD, CNC, and hand sculpting techniques.

Step 1: Design

A friend of mine was building a custom home and wanted a one of a kind spiral staircase. He had determined the rise and run and how each piece would bolt together forming a helix with a 10” hole in the middle. Each tread would bolt to the one before it using long bolts and threaded inserts. Before we started the building project, we took the CAD model and added curves to every surface that wasn’t touched by feet. What we came up with was very organic looking and became the sculptural element to unify the three floors.

Step 2: Efficient Use of Material

Once we had a model finished, we had to figure out how we were actually going to build it. Luckily, he owned a machine shop with a CNC machine we could use. All of the wood we used came from a 150-year-old matchstick factory in New England. After the wood was delivered it was measured and put into the computer model to show the most efficient use of materials.

We were then able to cut the reclaimed lumber into the sizes we needed and glue the blocks together to load into the CNC machine. Since the reclaimed lumber had bolt holes and blemishes all over it, we either hid or accentuated them adding to the stair's character.

Step 3: CNC Milling

Now that we had the blanks glued up we could program the machine to cut them out with robotic precision. Using the model of the final stair tread combined with the model of the wood blank, we were able to use the CAM software to write tool paths to remove excess material leaving only our curved stair treads.

Step 4: Hand Sanding

After the stair treads got out of the machine they were still a little rough. Since this project was in Maine during the winter, the sanding would have to be done inside. We set up a little pop-up and put up some plastic walls. Sanding and grinding is a messy job and dust got everywhere, but the Dexter-style kill room helped contain the dust quite a bit.

Each tread came out of the machine looking like a topographical map. All curves were actually made of different layers with a bunch of "steps" that needed to be smoothed out. Using black spray paint, we could see exactly how much we had sanded so we could sand everything evenly. Very aggressive sanding discs were used to get the black lines to where they were close to disappearing. Then the medium grit was used to make the lines almost disappear followed by the fine grit until the black paint was all gone.

Step 5: Final Glue-Up

After all the treads were sanded they were lined up and organized by color and grain pattern. Then it was time for a dry fit and assembly. Each tread was pinned into the concrete with a stainless steel rod. The rod was epoxied into the stair tread, then epoxied into the concrete, as well as epoxied to the tread before it before tightening the bolts. It was a pretty complicated glue-up but once we got the process down it flowed smoothly. One issue we had was the concrete epoxy going off too fast in the mixing nozzle. We mitigated that a bit by putting it in a bucket of snow between glue-ups, slowing down the chemical reaction.

Step 6: Finishing Touches

After the treads and landings were all in place it was time to have some more fun. We weren't sure what we wanted the transitions to look like and to model something in the computer seemed counter productive. For transitions, we left plenty of wood to then be sculpted by hand. CAD and CNC are great for so many things, but certain things are better if done by feel. We decided that the most simple curve would be the most elegant. One transition was done in a matter of hours one day, the second on the following day, then both were touched up at the end of the second day. It would have taken longer to model what I did in the computer than it was to make it in the physical world. Plus, when I tried to come up with something in CAD there were too many options. When presented with the raw form in real life, it was clear what needed to happen.

When it was all sanded and felt great to the touch it was time to hang plastic on the walls and oil the stairs. We used a product called Waterlox that worked great. If you've ever oiled a nice piece of wood, you know how satisfying it is to completely transform a wood project. It brings out all of the grain, deepens all of the colors, and lets the true character of the wood shine through.

In the end, this project was a huge success. The rest of the home is unique and stylish. There's a strong industrial feel with a lot of exposed concrete and steel, and this wooden spiral staircase with a TON of curves stands as a great contrast.

Many hands and minds made this project so successful. Huge thanks to Tom West, Tim Bickford, all the guys at Limerick Machine Co., and Doug Ruuska.



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    49 Discussions

    Oh my days! That is so gorgeous.

    I wish I had the skill and time to approach the wonderful thing you have created


    11 months ago

    JeffS2, check the note at the bottom left of the comment box: "We have a be nice comment policy. Please be positive and constructive." You should try it sometime. People who mentioned safety were not 'bickering,' they were making an important point--physical safety--and obviously the creators of this lovely stair were already or were made aware of it, because they added the rail proposed by several here, myself included, rather than try to bribe the inspector, as you seem to suggest. Another problem for me is what appear to be extra-thick treads, which can be a trip hazard. And thanks again to DennisO22 becaue now we all know the difference between helical and spiral stairs, and can amaze and dumbfound our friends!


    11 months ago

    Very nice / COOL work!

    Reminds me of the stair case that Sam Maloof made for his house.

    Are you planning on adding a Hand Rail to add a little safety to it; one slip on this could be very dangerous and possibly fatal.

    Thank you!

    It's beautiful, they really did a good job on it. I love just how yellow pine looks even before it's finished. But, when this wood is clear coat finished only one word describes it & that word is WOW!! While a spiral staircase is nice & is great if you have limited roon, personally I don't like them. I've been up & down them a lot & to carry something up or down, their the pits. Sorry, that's just my view on it.

    1 reply

    Agreed, I would never want to move furniture up and down this thing. Luckily there are large doors on all 3 floors. This staircase was created to save space. The previous 600 sqft house was grandfathered in so if the owner wanted a bigger house he had to build vertically.


    11 months ago

    Great salvage, great construction, thing of beauty. But dangerous! All helical (thank you, DennisO22!) stairs are risky but this one is especially so. Can't be sure, but the treads seem pretty narrow, significantly reducing one of the few precautions you can take on these stairs: always step on the outside of the the curve. Treads also seem extra thick, another hazard, if a lesser one. Please add a handrail. Relying on the center post or the wall to save you is fine--until you fall. Also it presumes you will always have both hands free. Kids should never be allowed near this thing. (Building inspectors, too, in most areas.)

    1 reply

    There was an outer handrail added after the photo was taken. It's actually really comfortable to walk up, unlike helical stairs built around a center post. The dimensions are based on a standard rise:run of 7":11". The only part the inspector wouldn't like is the >4" gaps between the treads. Otherwise, with the handrail it's totally legal.

    put together with no nails. granted the CNC staircase is great. the staircase in the Loretto Chapel is wicked impressive.

    loretto staircase.png
    3 replies

    Agreed, I still haven't seen it in person but that staircase is pretty stunning. It's on my list of things I must see.

    Is that the place where they have no idea how the person that made it bent the wood to make it... Like 300 years ago?

    I think I've been there, pretty cool.

    Stunning design and implementation! Love this!

    You take my breath away. They really did a good job on it.

    I have always wanted one. I would love to build my own. I would probably do mine in steel. I worked in steel for years. Somewhere there was a winding staircase when I was a kid, and every time I tried to go up it, I would trip and fall on my knees. you have to move very slow and methodical. Thanks,

    I can only imagine how much this cost to make. Definitely more than my car....

    It's a piece of art. Very nice job and thanks for sharing!

    Beautiful to look at, but at 76, terrifying. One slip and I would be dead and probably my cats would be too.


    11 months ago

    just don't walk down in your socks. if you slip you'll be three floors down real fast. I agree with another post here about circular stairs. there are good reasons building codes basically don't like them, at least not that small a diameter.