Forming a Concrete Circular Staircase

A 3D Sketch plan determined the correct cantilever steel placement in the walls. Jerry and Adam Jaksha decided against a solid rail. Instead, they used a bent wood rail.

Five-in.-thick foam/concrete wall forms were hot wire cut to allow for the 10-ft. radius. A lot of packing tape held the foam together.

Three-in. reinforced concrete rods carry the cantilever loads.

Steel rods supported the curved foam wall. The concrete was placed in 2-ft. lifts and vibrated with a sander.

Full 360-degree winder required a cast-in-place circular cantilever beam that supports the floor and landing. The open half of the beam was formed on the lower floor and raised into place. Then it was cast integral with the floor.

Stair forms 3/4-in. thick were stacked from the center post and rotated around a 2-in. steel center tube. They are rotated to become forms for the steps.

U-bolts hold stacked stair form boards and allow them to rotate.

The stair ramp form was made with fiberglass skinned foam. Two forms were made and the ramp was poured in three sections.

Adam Jaksha sets the steel. The team was unable to find a way to engineer it. The cantilever and curved hyperbolic shape of the stair made a rock solid shape. The cantilever steel was sufficient.

Pictured is the first ramp pour.

When the stair ramp was complete, the ramp measured 3 in. thick and cured for a week. The concrete had approximately 1-in. slump with a superplasticizer, and the w/c ratio was approximately 0.4.

They rotated the plywood created form steps. They built 24 5 1/2-in. steps with a 12-ft. total rise on 360-degrees.

Then foam walls were plastered and the bottom of the ramp received a skim plaster coat.

The result is a beautifully designed staircase.

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