Spiral Staircase Kit Basics

Designing and constructing a spiral staircase is a challenging project, but a modular system can simplify the process. Certain manufacturers sell spiral-staircase kits, and this article shows how a kit-built spiral staircase is reassembled in a new home after being reclaimed from another job site. In general, kits include treads, landing, balusters, handrails, hardware and accessories. There is nothing to weld or seal. Our team has built a few of these over the years, and this article shares the basic steps of spiral-staircase kit construction.

Planning & Ordering a Kit

When it comes to installation and assembly, the spiral-staircase kits vary in design, so consider the kit’s features when making your selection. For example, some kits may include a spacer system to adjust riser height, rather than rely on an exact height measurement between floors.

Another key factor is the directional turn of the spiral. Most manufacturers produce a specific unit based on the rotational turn (clockwise or counterclockwise) of the spiral for specific installation, so be sure to order a kit that fits the intended job site. Determining the direction of a spiral requires careful planning and measurement to avoid a restricted or blocked floor exit at the top or bottom of the staircase.

You should also order a kit to accommodate the upper landing configuration of the site. Make sure the staircase can be fitted to a square opening through the floor, or to a floor without an opening such as a balcony or mezzanine.

When ordering a staircase kit, first measure from the finished floor on the top level to the finished floor on the bottom level of the proposed stair location. This determines the exact staircase height required for installation.

To determine the correct diameter of the staircase, measure the area of available floor space. The finished space should be at least two inches larger than the total staircase diameter.

“When it comes to installation and assembly, the spiral-staircase kits vary in design, so consider the kit’s features when making your selection.” 

Site Preparation

The upper and lower landing will require sturdy construction to support the staircase.

As mentioned earlier, the spiral stair shown in this article was reclaimed from a construction site, so rather than ordering a staircase to fit the house, pro contractor and homeowner Adam Davis reconstructed the house to fit the staircase. Davis was in the process of renovating an unfinished basement into a bedroom/bathroom combo, so he cut stairway access through the ceiling and reframed the joists with reinforced headers surrounding the upper exit. The spiral stair now connects the upper level to the new living space in the basement. 

Note that homeowners should consult a professional remodeler or engineer before altering the framing of their house, because doing it incorrectly can seriously compromise the structural integrity of the building.

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This article covers the installation of a reclaimed metal spiral staircase. The homeowner (and professional contractor) Adam Davis cut stair access through a basement ceiling to connect the upstairs to a new fully finished living space which he was renovating below.

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Davis reconstructed the opening with reinforced headers and support for the floor joists. If you’re not experienced with house framing, then consult a pro builder or structural engineer before altering the framing of your home.

Staircase Installation

This reclaimed staircase included no instructions, so installation basically involved reassembling what Davis had dissembled in the past.

After finishing the new staircase opening with trim, drywall and paint, Davis temporarily bolted the upper metal landing (which serves as the top tread of the staircase) into position.

Once in place, it served as a control point to measure downward and plumb, determining the position of the corresponding bottom plate at the center of the staircase location.

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Davis screwed the bottom plate to the concrete foundation with Tapcons. The center post of the staircase mounts over a cylinder in the bottom plate and tightens in place with set screws.

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Each metal staircase tread includes a hollow sleeve that slides over the metal post. We removed the top landing plate so we could install the treads, which slide down and swivel independently around the post. We could then move the treads into the desired position according to the spiral path.

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Each tread swivels independently around the center post for easy adjustment.

On the staircase shown, the treads are snugged into place with set screws, but they don’t get completely tightened until installation of the handrail.

Handrail Installation

This staircase included a rigid, contoured handrail shaped to match the flow of the spiral. The handrail is supported by threaded metal balusters which fasten with screws to the treads. Each tread supports two balusters. The tops of the balusters insert into corresponding mounting holes on the underside of the handrail, and they’re then fastened in place with hex screws.

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Handrail assembly is a two-man job. One person needs to position the rail while a second person connects the balusters. We recommend connecting the bottom baluster first then a second baluster about halfway up the rail. You should be able to count the holes on the treads and handrail to determine the matching holes when connecting the second baluster.

Once you have the rail supported by at least two balusters to balance its weight, assembling the rail gets easier. You can then shift the treads inward and outward to adjust their position when inserting the balusters. The appropriate spread and final placement of the treads is determined by matching the balusters to the rail holes.

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After all the balusters were installed and tightened into place, we tightened down the set screws of the treads to strengthen the staircase and arrest any movement.

Complete the installation by mounting the top landing plate over the center post. Bolt the landing securely to surrounding floor frame.

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Finishing Touches

Davis gave the new spiral staircase a full cleanup and paint-down. He also hired a welding contractor to construct a metal handrail around the upper landing, which provides extra safety and matching black paint for a sleek, finished look.

SIDE NOTE

Pro Tip for Hiding Fasteners in Laminate Flooring

When creating the opening for the new spiral staircase, professional builder Adam Davis wanted to conceal the new fasteners in the flooring. To do so, he used a heat gun to warm the adhesive of the laminate flooring, which released the glue and enabled him to peel it backward. He then drove screws through the subfloor into the framing. The screws were then concealed by the laminate flooring during the final phase of the project.

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