The important numbers and features describing spiral staircases

14 May 2025

Among the topics related to spiral staircases, it is certainly worth taking stock of issues such as dimensions of a spiral staircase and other aspects related to it, without going too far into technicalities-details that give an idea of the machinery behind efficient design.The need,more relevant today than ever, especially for those living in cities, to optimize spaces, particularly living spaces, pushes architecture and interior design toward strategies for better management of every element. 

This is also true for the stair structure: combining functionality, space saving, and aesthetics is the ultimate goal of any well-designed project; we have often discussed the role of the spiral staircase in this context, not coincidentally also called a space-saving spiral staircase, and how variations on the theme of the modern spiral staircase can have a beneficial effect, especially in interior design.

If you want to choose from the spiral staircases for sale you need to know some things.

Spiral stair dimensions: ideal diameters and the numbers that count

We have frequently addressed the topic of the spiral staircase. Its most obvious characteristic is its verticality, which, regardless of diameter, ensures a small footprint and therefore saves horizontal space compared to traditional straight stairs. When space optimization is a major concern, smaller diameters, even down to a semi-spiral staircase, make the indoor spiral staircase or even the outdoor spiral staircase an ideal option. 

If you need information to choose from the spiral staircases for sale, let’s review the core structure: a classic spiral stair includes a central support from which the steps radiate, whether the plan is round, square, or elliptical. A helical stair is structurally different, as it lacks a true central pole and instead consists of helices that define the structure. Some variants, called spiral helical stairs, are a sort of hybrid and feature an open central column that significantly alters the anatomy.

But let’s look at some important figures: guidelines provide direction on minimum dimensions, ramp development, and other factors, with a clear distinction between primary and secondary private contexts (with exceptions or variances possible); the minimum diameter for a circular or square spiral staircase should be 160 cm; in secondary private spaces, this could be reduced to 120 cm.

It is technically feasible to go down to 100 cm in very tight areas, but in that case, clearance would drop below 50 cm, which is quite minimal. Anything is possible, but practical use and intended users must be carefully considered; for a diameter of up to 160 cm, the step rise (12 per revolution) would fall between 20 and 24 cm; larger diameters, up to 2.5 meters, typically have 16 steps per turn and risers between 18 and 22 cm. The ratio between slip treads and riser height is crucial for safe and comfortable use. Ideally, treads should be no smaller than 25 cm, especially for safe descent

Start building your perfect stair solution: square spiral stair, dimensions and benefits

Beyond the classic circular spiral staircase, most common in tight spaces, there are also helical variants and the square spiral staircase among spiral staircases for sale; the square spiral staircase is a modern evolution: still curving, but better suited for broader installations. It fits well in corner spaces, such as between two walls, where the design options let you reclaim precious centimeters to make climbing easier and more comfortable.

Being able to flush-mount the steps to the wall increases usable tread surface, and even a few centimeters can make a big difference. In a square staircase, a handrail can sometimes be omitted, unlike with a classical spiral. As for minimum size, the square hatch must be at least 1m x 1m. Beyond that, choices for building materials, finishes, and styles remain as flexible as with any other spiral staircase kit.

The angular geometry may lose some of the magic of the spiral form, but it is much appreciated in staircase design for modern spiral spaces and environments that don’t favor curves.

Spiral stairs for every setting: indoor and outdoor

The spiral staircase is well-suited for both interior and exterior use. Elegant and iconic with its spiral ascent, it has few equals in visual impact and outperforms traditional stairs in terms of space saving. Dimensions, position, and the possibility to customize various elements make any spiral staircase for sale a discriminating factor between an average and an outstanding project.

Circular, helical, or square, in metal spiral, wooden spiral, or any other finish you can imagine, from essential to luxurious, spiral staircases are found in homes and public buildings alike. Almost anything is possible if regulations are followed (in Italy): NTC 2018, the Building Code, Law 13/1989, DM 236/1989, local codes, Ministerial Decree of 30/11/1983, and UNI standards for prefab stairs.

The key difference between an indoor spiral staircase and an outdoor spiral staircase is exposure to the elements and the resulting effects on stair parts and building materials. If you are choosing among spiral staircases for sale, you have to know that for outdoor spiral use, a galvanized spiral model or industrial spiral stairs may be required to withstand harsh weather, ice, and rain.

Proper water management is essential, as water accelerates wear: specific treatments and coatings are applied, and any well-designed quality staircase can remain beautiful and durable. Even an outdoor spiral can match the style and refinement of its indoor counterpart, adding charm and functionality to your living room or garden.

Choose your spiral staircase: customized, durable, and stylish design spiral stairs

With a wide range of solutions, finishes, and wood species, you can truly build your stair and put the design in your hands! Whether you prefer a metal spiral staircase, steel spiral, or solid wood, each component can be tailored: from custom spiral geometries to custom color schemes; modular and pre-configured models offer easy installation, and low maintenance options ensure your floating stairs or spiral units will last over time.

A spiral staircase is not just a structural choice, it’s a statement of space, style, and intelligent design: if you’re seeking a compact, durable, and beautiful stair solution that will fit your budget, then metal spiral staircases or indoor spiral stairs could be the perfect solution for your space.

Discover new opportunities through some spiral staircases for sale by Officine Sandrini

If you want to elevate the design of your interior, spiral staircases can become the real distinguishing feature. With their refined style and perfect functionality, they represent an ideal synthesis between aesthetics and practicality, perfect for modern and contemporary environments.

Discover the exclusive proposals of Officine Sandrini: fill in the form and receive our brochure for free. Give yourself a custom space, where every detail is designed to amaze and inspire!