What Is the Floating Calculator?
Floating stairs are the showpiece of modern architecture: treads that cantilever from hidden structure and read as if they hover in mid-air. The look is simple; the engineering is not. Every floating stair hides its support in one of three ways: individual steel brackets or plates bolted through the wall (a true cantilever), a central steel spine, called a mono-stringer, that each tread bolts to, or a concealed wall-mounted stringer hidden behind drywall. This calculator sizes the structural side of that choice. Enter the total rise, tread depth, width, material, and thickness, plus the support type, and it returns the cantilever load per tread, the required bracket spacing and fastener count, the minimum wall framing those loads demand, and the expected deflection under a 300-pound concentrated load. That load figure is not arbitrary: code requires stair treads to carry concentrated loads, and on a floating stair each tread carries its share alone, with no stringer underneath to spread it. The calculator also flags the two failure modes inspectors see most: wall structure that cannot carry the loads (standard 2x4 framing with no blocking will not do it) and deflection that feels like bounce even when nothing is technically failing. Expect stricter permit scrutiny than a conventional stair gets, so every result pairs with the code checkpoints your inspector will ask about. Treat the output as your engineering brief, not as a substitute for it: this stair type genuinely needs a structural engineer's review in most jurisdictions.
How to Use This Calculator
- Enter the total rise from finished floor to finished floor. The riser count and the per-tread load both derive from this number.
- Set tread depth, width, material, and thickness. Thicker solid treads and steel pans deflect less, which matters because every bit of bounce is felt directly underfoot on a cantilever.
- Choose the support type: wall-cantilevered brackets, mono-stringer spine, or concealed wall stringer. Each changes the load path the calculator checks.
- Describe the wall construction: stud size and spacing, whether blocking or a steel plate will be added, and the sheathing. The wall is part of the stair structure, so this input is structural, not cosmetic.
