For a floating-stair quote, floor-to-floor height is the vertical difference between the intended finished walking surface at the lower level and the intended finished walking surface at the upper level. If both floors are complete, record those two elevations from the same reference. If either floor is unfinished, send the current structural elevations and the planned finish thickness at each level separately, then label the resulting height as projected. Do not substitute floor-to-ceiling height, an opening length, or an unlabeled number from an old plan.
Senmit’s floating-stair quote form asks for “Total Floor-to-Floor Height” in inches or millimeters. The number helps start a design conversation; it is not, by itself, an approved stair layout or a fabrication dimension. Use the worksheet below to make your measurement understandable to the designer, contractor, and person who will verify it in the field.
First, identify the two surfaces
“Finished floor” means the surface people will walk on after the planned flooring assembly is complete. Label the lower and upper surfaces on the same section drawing or dated sketch. The finish may include flooring and other layers specified by the project team. A rough slab or subfloor can be a useful reference, but it is not interchangeable with the final walking surface.
Use one elevation datum for both levels. If the drawings show elevations, record their revision and what each elevation describes. If the floors are already built, ask the project team to document the two finished elevations from a consistent benchmark. Do not lean across an open stairwell or remove temporary protection to obtain a number; an inaccessible condition belongs on the contractor’s field-survey list.
Choose the correct case before entering a height
| Site condition | What to record | What to put on the early quote request |
|---|---|---|
| Both finished floors are in place | Lower and upper finished-floor elevations, common datum, measurement date, and verifier | The difference between those two finished elevations, marked “field measured” only if the responsible team has actually verified it |
| One or both finishes are not in place | Lower and upper rough reference elevations plus each level’s planned finish build-up and drawing revision | A calculated projected finished floor-to-floor height, with all four inputs attached |
| Plans and built conditions disagree | Both values, their sources, and the unresolved discrepancy | “To be verified,” not a silently selected number |
If the finished floors exist, subtract their elevations
- Mark the lower finished walking surface. Note whether the reference is the actual installed finish, not the slab or subfloor beneath it.
- Mark the upper finished walking surface. Use the same project datum and units as the lower level.
- Subtract lower from upper. Record the two source elevations beside the result so another reviewer can reproduce it.
- Label the record. Include the location, date, drawing or survey revision, and who took or verified the measurement. If the floor varies or the stair has a landing, ask the designer which locations control the proposed flight.
A value copied from a listing or a builder’s preliminary plan is not a field measurement. It can still be useful for an early feasibility conversation if its status is clear. Final stair geometry depends on the approved project documents and the field conditions the responsible team accepts.
If the floors are unfinished, show the finish math
When both rough elevations refer to the comparable surfaces immediately below their planned floor finishes, use this accounting identity for an early estimate:
Projected finished floor-to-floor height = upper rough elevation − lower rough elevation + upper finish build-up − lower finish build-up.
For example, suppose the upper rough reference is 111 inches above the lower rough reference, the planned upper finish adds 3/4 inch, and the planned lower finish adds 1/2 inch. The projected finished height is 111 + 3/4 − 1/2 = 111 1/4 inches. This is an arithmetic illustration, not a Senmit dimension, a recommended riser count, or permission to fabricate from preliminary plans.
The subtraction changes if the references do not describe comparable layers. For example, a top-of-slab elevation and a top-of-subfloor elevation cannot be combined with guessed finish thicknesses as if they were the same kind of starting surface. Have the architect, builder, or surveyor reconcile the drawing notes first. Keep inches and millimeters separate; do not mix units in the form or sketch.
If finishes are still being selected, give the current design allowance and mark it as unapproved. When flooring, underlayment, tile setting material, or another layer changes, recalculate the projected number and issue a dated revision. A recent carpentry discussion about a stair with one taller riser and a home-maintenance discussion about uneven existing stair heights illustrate why finished-level assumptions matter. Those discussions describe customer problems, not engineering or code authority.
Keep three commonly confused dimensions separate
| Dimension | What it describes | Why it is not a substitute |
|---|---|---|
| Floor-to-floor height | Vertical separation of the intended lower and upper finished walking surfaces | It establishes total rise, not available horizontal space or headroom |
| Stair opening length and width | Horizontal opening limits along and across the stair | An opening can be accurately measured while the floor elevations remain provisional |
| Ceiling height below the stair | Vertical clearance to a ceiling or soffit at a defined location | It is not the height between the two finished floors |
Senmit’s form requests these as separate fields, along with the stair type and information about nearby wall structure. For a coordinated plan and section, see the existing floating-stair section drawing checklist. For the later field-acceptance stage, use the site-tolerances and field-verification guide. This page is specifically about obtaining and labeling the early floor-to-floor number.
Send the source of the number, not just the number
Attach a one-page measurement record to the quote request. Include:
- Project location and whether this is new construction or a remodel.
- The intended lower and upper finished-floor surfaces, identified on a current plan or section.
- Both source elevations, the common datum, units, and the resulting floor-to-floor height.
- Any unfinished-floor build-ups, each marked confirmed, allowance, or still unknown.
- The date, drawing revision, measurement owner, and the planned field-verification milestone.
- Opening length and width, ceiling height below the proposed stair, site photos, and the preferred mono-stringer, cantilever, or zig-zag direction, when known.
State whether the result is “field measured,” “calculated from current plans,” or “concept only.” A brief that preserves uncertainty gives the quote team a better starting point than a false-looking precise number. Senmit’s form also accepts architectural drawings or site photos; upload the current set rather than mixing revisions.
Set a verification hold point before custom fabrication
Early quote dimensions may change as floors, landings, walls, and finishes are built. Name the person who will recheck the finished reference elevations, record when the site will be stable enough, and specify who accepts the final dimension for design and fabrication. Do not treat this article or a generated illustration as an installation instruction or structural approval.
The International Code Council’s 2021 IRC riser provision is model-code context for why the final stair must be reviewed as a coordinated flight; it addresses how riser heights are measured and their uniformity. The code edition adopted by the project’s jurisdiction, any amendments, the project classification, approved drawings, and the authority having jurisdiction control the actual requirements. A floor-to-floor measurement alone does not establish compliance or determine the number of risers.
Senmit’s floating-stairs overview describes custom design drawings and installation guidance, and says installation is not included in the quote. Confirm the responsibilities for field measurement, engineering, permitting, support preparation, and on-site installation in the project-specific proposal.
Bottom line
Measure or calculate between the two intended finished floors, show how the result was obtained, and label what remains provisional. Then submit the height with the opening dimensions, drawing revision, and photos through Senmit’s floating-stair quote form. The project team should verify the accepted dimensions before any custom stair components are released.
