The Complete Guide to Calculating and Drafting Stairs with AutoCAD and NanoCAD

Introduction

Staircase design is a crucial aspect of architectural drafting, requiring precision, adherence to building codes, and functional aesthetics. Whether using AutoCAD or NanoCAD, mastering stair calculation and drafting ensures efficiency and accuracy in your designs. This guide walks you through the process, from fundamental calculations to drafting in both CAD platforms.

Understanding Stair Calculations

Before drafting, it’s essential to calculate stair dimensions accurately. The key factors include:

1. Rise and Run

• The rise is the total vertical height from one floor to another.
• The run is the total horizontal length the staircase covers.
• The ideal riser height is between 6.5″ to 7.5″ (165-190mm), and the tread depth is typically 10″ to 11″ (255-280mm).

2. Number of Steps Calculation

Formula:

Since the number of treads is always one less than the number of risers:

3. Staircase Slope (Angle)

The standard stair angle ranges from 30 to 37 degrees. To calculate the angle:

4. Headroom Clearance

Building codes usually require at least 80 inches (2032mm) of headroom clearance above each step.

5. Width and Landings

• Residential stair width: 36 inches (914mm) minimum
• Commercial stair width: 44 inches (1118mm) minimum
• Landings should be at least the width of the staircase and occur every 12 feet (3658mm) of vertical rise.

Drafting Stairs in AutoCAD

Step 1: Set Up the Drawing

1. Open AutoCAD and set the units (UNITS command) to inches or millimeters.
2. Start a new layer for the stairs (LAYER command) and set it to active.

Step 2: Draw the Stair Outline

1. Use the LINE or POLYLINE command to outline the total rise and run.
2. Divide the total run into equal tread widths.
3. Offset each tread using the OFFSET command.

Step 3: Draw the Risers and Stringers

1. Use the ARRAY command to replicate riser lines across the stair span.
2. Draw the stringers on both sides using the LINE tool, aligning them to the risers.

Step 4: Add Dimensions and Annotations

1. Use the DIMLINEAR command to add dimensions for rise, run, and tread depth.
2. Label stair direction using TEXT or MTEXT.

Drafting Stairs in NanoCAD

Step 1: Create the Stair Layout

1. Open NanoCAD and start a new drawing.
2. Set up layers for clarity (LAYERS panel).

Step 2: Draw the Steps

1. Use the LINE or POLYLINE tool to create stair boundaries.
2. Apply the ARRAY function to distribute risers evenly.

Step 3: Add Details and Finalize

1. Draw the handrails and balustrades if required.
2. Annotate dimensions using the DIM command.

Exporting and Finalizing the Drawing

1. Check for Accuracy – Ensure all dimensions comply with building codes.
2. Use Layers Properly – Assign treads, risers, and annotations to distinct layers.
3. Export as DWG or PDF – Use EXPORT or PLOT commands for sharing.

Calculating and drafting stairs in AutoCAD and NanoCAD requires a balance of precision and compliance with building standards. By following these steps, you can create professional, code-compliant stair plans efficiently. Whether you are a beginner or an advanced drafter, refining these skills ensures your stair designs are both functional and aesthetically appealing.