What Stair Millwork Shop Drawings Must Show for Safe Fabrication

A custom wood staircase is both a structural element and an architectural one. It has to meet code requirements enforced by building inspectors, structural requirements coordinated with the engineer, and aesthetic requirements from the architect or designer — all at the same time. The shop drawing that supports its fabrication needs to address all three layers simultaneously. A drawing that handles the design beautifully but misses a code dimension will produce a stair that fails inspection.

Our millwork shop drawing services cover custom wood stair packages including stringers, treads, risers, newel posts, railings, and baluster systems. Here's what a complete stair millwork drawing set requires.

The Stair Section: The Most Important Drawing in the Set

The stair section — a vertical cut through the stair flight showing the stringer, treads, risers, landing, and railing in profile — is the single most important drawing in a stair millwork package. It establishes the tread-to-riser geometry, verifies code compliance, and shows the relationship between the millwork and the structural framing.

The section must show:

• Total rise and total run: Overall vertical height from finish floor to finish floor, and horizontal run from face of first riser to face of last riser
• Individual riser height and tread depth: Each step dimensioned, with the nosing projection called out
• Stringer profile: Whether open (cut stringer) or closed (housed stringer), with the stringer board depth dimension and the remaining board depth after the step is cut
• Handrail height: Measured vertically from the stair nosing to the top of the handrail, at both the top and bottom of the flight
• Landing dimensions: Landing depth (IBC requires minimum 36" in the direction of travel) and relationship to the stair flight
• Structural bearing: Where the stringer bears at the top and bottom — on a beam, a header, a ledger, or the floor framing

Tread and Riser Code Requirements

The IBC and IRC have different dimensional requirements depending on whether the project is commercial (IBC) or residential (IRC). The drawing must reference the applicable code and call out the governing dimensions explicitly.

The maximum variation of 3/8" between any two risers in the same flight is the dimension that most often causes problems. If the structural floor slab or framing isn't at a consistent height, the stair drafter must either work with the structural dimension or flag the discrepancy so the GC can correct the floor height before the stair is installed.

Newel Post Details

Newel posts are the structural anchor for the railing system — they need to be drawn with both the aesthetic detail and the structural attachment. Two primary newel construction types appear in residential millwork:

Turned solid newels are lathe-turned from a single piece of hardwood, typically 3.5"×3.5" or 4"×4" square at the base with a turned profile above. The drawing must show the turning profile, the overall height, and the attachment to the stair structure — typically a threaded rod through the center of the post into the framing.

Box newels are assembled panels over a structural 4×4 post or steel rod. The box newel drawing shows the panel dimensions, the mitered corners, the cap detail at the top, and the base panel detail. Box newels are larger and more formal than turned newels — 5"×5" to 8"×8" face dimension is typical — and they require a separate structural post inside that the box panels are built around.

Handrail Profile and Connection Details

The handrail profile is specified by a catalog number from a stair parts supplier (such as the L.J. Smith or Stair Supplies product range) or drawn as a custom profile in large scale. The graspability requirement — handrails must be graspable, meaning the cross-section must be between 1.25" and 2" in diameter for a round profile, or within specific cross-section constraints for non-round profiles — needs to be confirmed in the drawing.

Rail connections at the newel posts — whether using rail bolts, rail fittings, or mortise-and-tenon — must be detailed. Rail fittings (the turned transitional pieces at the starting step and landing) are shown in elevation at large scale, since getting the fitting type wrong affects the rail geometry at the transition.

Baluster Layout and Spacing

The baluster spacing must be calculated to prevent any 4" sphere from passing through. On a straight stair with uniform riser heights and a consistent rail angle, this is a straightforward calculation. On curved stairs or stairs with landing returns, the spacing geometry becomes more complex and needs to be verified for each section.

The drawing should show the calculated baluster spacing and the number of balusters per tread (usually 2 per tread in residential work). Where two balusters per tread doesn't achieve 4" clear spacing, 3 per tread is required — and the drawing must call this out explicitly rather than leaving it to the installer's judgment.

Coordination with Structural Drawings

Custom wood stairs require coordination with the structural engineer's drawings. The millwork drafter needs to know: the structural floor opening dimensions, the beam or header that the upper stringer bears on, the floor framing depth at the landing, and whether any structural posts are in the stair footprint that affect the newel layout.

Conflicts between the millwork drawings and the structural drawings — a beam that lands where the newel post needs to go, or a floor opening that's too narrow for the specified stringer width — need to be caught and resolved before fabrication. The time to find these conflicts is in the drawing phase, not on the job site.

For more on coordinating millwork with other trades, see our guide on the complete millwork shop drawing checklist. Our stair millwork drawing rates vary by stair configuration — straight flights run 8–14 hours, curved or switchback stairs with complex railing systems typically run 16–24 hours.

Frequently Asked Questions