Floating Circular Concrete Staircase

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Introduction: Floating Circular Concrete Staircase

About: DIY is a way of life for me, building a geodesic dome house, a swimming pool, solar water and house heaters, passive solar house (in Nebraska), and recently a concrete house and pool in Mexico, For the las...

This unique circular staircase at my casa in Mexico has no center support. It's 24 steps allow a 12' rise in a 10' diameter circular stairwell. I designed an built it with help from my son.
Circular stairs usually need a center support, but I wanted to have the center open, so I designed this one to cantilever from the wall, leaving a 3' open center.
To accurately form the wall and steps, I cut a dozen 5' -1/6's from 3/4" 
Rotating same boards around the pipe gave us the riser forms to pour the actual steps onto the ramp.

Step 1: Sketchup Plan

Drawing it in sketch up made it possible to calculate step rise and run, rebar placement, and step placement.

Step 2:

The circular wall that holds up the stairs is made from 5" foam blocks that leave a 3"  vertical and horizontal void for concrete and rebar. These styrofoam block forms are made in Mexico. I also used them for most of the walls in the house.
Bars to hold the steps had to be placed  in this wall as it was built, so I needed to know exactly where to place them so each step would have a rebar in tension off the wall. By drawing this staircase in 3/d (sketchup) , I could place the bars exactly.  The ramp/steps
We poured the ramp and steps 6 months after the wall was built.

Step 3: Landing and Circular Support Beam

Because the steps ran 360 degrees, the landing had to support both the staircase and the upstairs floor. We formed a circular 1/2beam on the floor and lifted it up to pour the complete circular beam.
Half the beam was in the wall, and the half you see supports the floor.

Step 4: Forming the Spiral Ramp

To accurately form the wall and stairs, I used a 20' 2" steel electric conduit pipe as a temporary center post.
I used a 2" u bolt fastened through the end of 6" wide plywood board to make sure the wall was round. 

The same boards stacked and rotated to form the bottom support for a foam/fiberglass form we made by tweaking 1" beadboard to the needed warped shape, then fiberglassing it.  We made two sections,glassed both sides with epoxy resin.


Step 5: Pouring Ramp

Rebar gets added to the bars coming out of the wall, and an inside form of 1/4" plywood added to the inside.

The ramp was poured in 3 sections, glued at the joints with latex concrete adhesive. This let us reuse the fiberglass and support forms, just by rotating the plywood boards and locking in place.
The concrete was very high strength, mixed on site using super plasticizer to reduce water content.
All the concrete was consolidated with a spud vibrator.
The ramp is 3 inches thick.
You can see the "U" bars sticking out. They give a physical lock to the steps poured next.

Step 6: Rule # 1 Celebrate Victories

On a big long project like this it is important to break it down into smaller parts, just like an instructable.  You can then enjoy the successes that keep you going.
With only myself and my son Adam working on this part time, it took many weeks to complete, with many celebrations along the way. 

Step 7: Steps

The ramp support forms get rotated to the top of the ramp and become riser forms.
Because the forms stack on each other at the main tube, all I had to do was level them and set them at my marks on the wall that came from the sketchup drawing a year earlier.

Step 8: Finish

A  plaster finish on the wall and you have one solid staircase, with less than 1/8" deviation between step rise and run.
Someday we might cap the steps with tile or wood, but they look very sculptural as is.

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    78 Comments

    Hi, I have a spiral staircase, an iron structure, but with problems on wall supports, and upside-down step frames...

    It goes on for three floors (51 steps), with 100cm radius (3 ft. or so), with a central iron pole of 10-12cm (4-5").

    Can I use this construction as a formwork to build it using concrete?

    I think that by using vertical pieces to 'close' the step and a frame underneath plus some rods and wall supporting nails I may pour the liquid concrete in that frame...

    What do you think?

    Thanks a lot.

    Emil from Greece (Crete island)

    P.S. By the way, great job with that floating staircase!

    1 reply

    Emilk, Hi from the USA. In the USA homes w/ no side rails are illegal so no permit will be issued. This is USA law. Mexico and Greece are different countries different rules. I love it too! My husband is an Architect who is a Master Architect, meaning he's top in Fires, ADA, Government laws on all things as well as the credentials for all things architecture. Personally I love this man and his son work. He's building everything to his specs and not through red tape. I agree w/ you. I know this is late but I saw it today and kudo's to this man/son. Awesome Everyone. This is beautiful.

    Very beautiful. I have built something similar out of wood once (I'll NEVER do it again...). I would have never thought to use concrete, though. Wow.. just... wow.

    THAT IS AWSOME! I have doodled designs for a house I would build if I won the lotto and it calls for a staircase something like this (though didn't envisage something as cool as this) in my design the centre area is not open to the stairs because I'd like a camera obscurer as the centre piece. great skills.

    I have seen many ables on this site but not one that can stand up to this and the work you (and your helpers if any) did. Amazing work. I even had to share this on other sites.

    Oh wow I adore this, I wish I had a more technical mindset to pull something like this off. I'm in awe of people who do. Nice work and amazing craftsmanship!

    love how fluid and smooth it looks. great job

    You are an artist, well a craftsman and an artist. This is a thing of beauty. I have designed and built curved staircases, but never envisioned this. I love it. Great instructable!!

    Hi Sajin, this is illegal in the USA. No rails means it's not safe so unless you're in his country or other countries where you can just build. My husband can help if you're in the USA.

    Looks like you will need an expensive steel spiral support beam. Steps would need to be welded on.

    Can you let us know in a year if it's still standing, and if any cracks have developed?

    2 replies

    over 5 years old and solid as reinforced concrete- no cracks

    It has been up over a year and has no cracks- way too much steel. When in doubt- add steel to your concrete. There is no give at all, like you would get in a wood stair.

    so beautiful I want this in my dream home. does it have to be holding onto a wall or is it strong enough to hold it self up?

    1 reply

    Since It has no center post I believe it needs the wall for support.

    It is possible that it has enough steel to act like a spring hanging from the circular beam, and supported by the floor, but I wouldn't bet on it.
    I didn't design it to stand without the wall.

    Any engineers out there who could do a computer analysis? Might make a good finite analysis project for a grad school engineer.

    Good work! I build ICF structures in BC, Canada, (using ICFs from Quadlock) Tell us more about those Mexican ICFs you used please.

    1 reply

    The icf blocks in Mexico are 3' x 5" wide x"8" high. They leave a 3" concrete rod vertical and horizontal centered every 8". Not too much insulation, but it is Mexico.
    We cut vertical slots with a soldering gun so we could bend blocks at the stairwell.
    We used lots of packing tape to keep things in line.

    A rather incredible set of stairs you have made there, but i see one flaw, no fireman's pole down the center!

    1 reply

    A fire pole would be fun. I have another spot for that- at my fire pole/elevator that will take me 12' down to the water. -- one of my next instructables...