04 / Method and field checks
How the stringer profile is formed
The planner divides the finished rise into equal risers under the lower of its 190 mm planning target and your project-reviewed maximum, then assigns one fewer structural tread runs because the upper floor acts as the landing. It plots the corner at each cumulative run and rise, measures the diagonal between endpoints, and adds 150 mm of end allowance on each side for a preliminary stock fit. The remaining throat is the stock depth minus the perpendicular depth of one step notch.
Worked layouts
The loaded US example has 84 in finished rise and 120 in available run, with 1 in tread thickness, 1 in nosing, 16 ft stock length, 11.25 in stock depth, 36 in width, and three stringers. It yields 12 equal 7 in risers and 11 structural runs of about 10.91 in. It remains an example: with no project-reviewed rise and run limits entered, the material list stays on hold.
For a 108 in rise and 120 in available run, the planner uses 15 risers at 7.2 in each and 14 treads at about 8.57 in structural run. The first cut corner is approximately (8.57, 7.2) in from the lower reference; the seventh is about (60, 50.4) in. If the reviewed project minimum structural run is 10 in, this run fails and no material order lines appear.
Measure, calculate, then verify the flight
Measure between finished floors and the unobstructed horizontal footprint; obtain the project's rise and structural-run limits; then compare the cut-mark table, throat, stock fit, and review reasons. Check the proposed end bearings and overhead clearance on site before copying any material line into an order. A failed geometry check leaves the drawing available for correction but no purchase quantities.
Mistakes to catch before cutting
- Using the finished tread depth as the structural run without separating the nosing projection.
- Measuring rough framing instead of the two finished-floor elevations.
- Assuming a profile view proves adequate overhead headroom or landing space.
- Ignoring actual lumber depth, bearing, connections, and support spacing across the stair width.
Stair layout questions
Why is there one fewer tread than risers?
The final rise reaches the upper finished floor, which serves as the last walking surface in this straight-flight model. A separate top tread or landing detail changes the construction and needs its own review.
Does the stock-fit result approve a stringer board?
No. It compares a diagonal length plus explicit end allowances with the entered board length. If stock fit or any other geometry check fails, the result keeps the layout but withholds every material line. Grade, species, throat, connections, support, and local rules still need project-specific review.
Where should I check headroom?
Measure the clear vertical distance above the entire walking line, including any overhead framing or soffit. This tool has no overhead geometry input, so its warning is a reminder to survey that space.
Published by MaterialNest for preliminary stair layout. The drawing cannot certify code compliance, structural strength, or permit acceptance; confirm critical geometry and construction with a qualified stair professional.
Source context and internal planning choices
The American Wood Council DCA 6 guide, based on the 2015 IRC, covers stringer spans, attachments, landings, guards, and handrails in its limited residential wood-deck scope (pages 20–22). It defers to local requirements; it does not approve this planner or a particular stair.
MaterialNest chooses the 190 mm planning-rise cap and 150 mm allowance at each stringer end for this preliminary model. Neither is a universal code limit or a bearing specification. Equal risers, one fewer structural tread run, diagonal stock length, and notch-depth arithmetic are internal geometry. The 355 mm run, 89 mm throat, 32 mm nosing, stringer-count, and 18-riser checks are review triggers in this implementation, not a complete compliance test. Passing them cannot establish adequate support or safe construction.
Source context and implementation assumptions checked September 27, 2026. This is a documentation reconciliation, not a professional stair-design review.