Draw Stair Tool

Draw Stair creates parametric stair assemblies for a range of plan shapes: straight runs, dog-leg, L-shaped, U-shaped, spiral, and straight-along-path. The tool includes an AI-assisted calculator that suggests a riser count and tread depth based on the total height and the ergonomic 2R + T ≈ 25" rule.

• Straight - single run from floor to floor.
• Straight Along Path - follows selected connected edges; useful for curved or sloped runs.
• Dog-Leg - two flights joined by a landing with a 180° turn.
• L-Shaped - two flights joined by a landing with a 90° turn.
• U-Shaped - two flights with a landing and a centre gap.
• Spiral - circular stair around a central post.

• Total Height - floor-to-floor rise.
• Stair Width - width of the flight.
• Tread Depth - horizontal run of each step (or let AI choose).
• Waist Thickness - structural slab thickness.
• Landing Depth - size of intermediate landings.
• U-Shape Center Space - gap between flights for U-shaped stairs.
• Target Riser - desired riser height; the tool clamps it to a safe residential range.
• Landing After Steps - manually fix the number of steps before a landing.

Enable AI Auto Tread to let the tool calculate the tread depth from the riser using the comfort equation 2R + T ≈ 25". The live metrics show riser count, riser height, tread depth, and waist vertical thickness. The built-in validation warns if risers exceed 7.5", fall below 4", or if treads are narrower than 10".

Auto Height From Roof can raycast upward to measure the clear height to a roof plane and use that as the stair height, minus the configured roof clearance.

For Straight Along Path, first select connected guide edges that define the stair run. You can right-click and choose Convert Path to Stairs, or open Draw Stair in path mode. The tool detects path length, horizontal run, and vertical rise, then either auto-fits the treads to the path or lets you set manual values.