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What are Cantilever Stairs?

Floating cantilevered stairs with platform

Cantilever stairs are made to have the stair treads appear to be floating in the air without support. To achieve this look the stair treads may have a hidden steel structure within or below the treads for support. Also, the steel support structure and stringer may be concealed in the wall, or be exposed. Thus, creating a refined or an industrial appearance. The stringer and steel structure are typically located on one end of the treads. Understanding the required weight-bearing load on the treads is critical to engineering a cantilever stair system that is properly designed to minimize flexing. Expertly engineered and artfully designed a cantilevered stair can add an element of interest and spaciousness to your home.

Floating cantilever stair treads against 
a stone wall.

1) Hidden Cantilever Stair Stringer and Structure

This project was designed to hide the stringer and structure inside the wall. There are three structural steel tube posts that run from floor to ceiling hidden in the wall with an 8-inch steel stringer attached to it on a diagonal. at the top of the stairs, an additional square steel framework was created for the landing and encased with wood. Each Tread has a double steel structure wrapped with oak to hide the steel system within it, resulting in a genuine work of art.

Drawing showing the structure of the one story cantilevered stair with interior support structure.

Creating cantilevered stairs starts with measuring the site, understanding the structure of the building, and existing load-bearing walls. To accommodate a cantilever staircase it may be necessary to build more strength and support for the stairs into the walls. Once this is understood it is important to make an exact drawing for the fabrication of the stairs and it may be necessary to run stress analysis on the structure. Understanding the site and the construction of cantilever stairs makes it possible to create a unique structure that will have optimal performance, safety, and style.

Exposed cantilever staircase showing the stringer protruding out of the wall with cable railings and steel supported wood treads

2) Exposed Stair Stringer with Cantilevered Landing

This staircase was custom crafted with the steel stringer partially exposed through the shiplap finished wall. Each stair tread is supported by an exposed structure to create an industrial styling that appears to zig-zag up the wall. To create the platform landing the stringer wraps around the corner while maintaining the exposure. Each railing post is designed to slice through the treads to hide the attachment hardware below the tread.

Drawing of cantilevered stair that wraps around the landing and transitions to the next floor.

Additionally, steel attachment plates were added to the top and bottom of the stairs and hidden in the floor and wall. This adds strength to stairs while providing the function of resisting torque. By understanding the torsional load on the wall a number of techniques can be used such as adding hidden attachement plates.

Exterior biased cantilever staircase with stone steps and steel supports

3) Partial Cantilever Stair with Stone Steps

This staircase leading from a garage entry to an upper-level pool and patio was designed with the stringer biased to one side along the concrete wall. Thus, establishing the look of a cantilevered stair while maintaining the strength and resistance to the torque that is required.

Rendering of stone steps on biased cantilever staircase.

When using a stone stair tread the strength of the staircase can not depend on the stone tread to add support and resist the torque of the staircase. Therefore, each tread support required a sufficient steel structure to prevent the stone step from cracking. Each tread support was designed with threaded rods welded to the support and projecting upwards into the predrilled stone tread. This approach solidly anchors the tread to the steel tread support.

Exterior Deck with Cantilevered staircase and IPE treads.

4) Fully Exposed Exterior Cantilever Staircase

A fully-exposed cantilevered staircase was designed for this home to transition from the deck to the yard. Choosing a thin Ipe tread for this staircase required the steel structure to be strong enough to support the thin treads. In addition, to support the stringer the deck structure was reinforced. Also, note that the stringer switches sides at the platform level to use the same steel support post and cantilever the landing.

Rendering showing the structure of cantilever stairs

Cable railings were chosen to maintain the open appearance and connect to the steel tread supports. The deck and steel posts are further supported by additional footers below ground.

Mesh image of stairs with rendering image for visualizing the finished product.

5) Digitally Measuring, Rendering and Analysis

Digitally measuring the site provides accurate scan data detail. This detail will provide critical pieces of information such as how parallel the building walls are to the floor. Using these measurements ensures the cantilever staircase will fit and function as required. Creating a rendering of the finished stair before fabrication allows for the visualization of a variety of decorative finishes before creating the final product.

Stress analysis of cantilever stair exaggerating deflection

At Keuka Studios, we custom fabricate residential and commercial stairs and railings to fit your style, space, and requirements. To learn more about how each cable railing project moves from vision to reality, take a look at our custom railing design process. We take pride in building craftsman-quality and commercial-grade stairs and railings for interior and exterior applications. Contact us to get started on your project.

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