Staircase Structural Design in Civil Engineering

Stairs are an essential part of any building. A well-designed staircase must be safe, comfortable, strong, and durable. In this article, we explain the basic structural design of a staircase step by step in an easy-to-understand way.

Stair Design

I. The Purpose of Staircase Design

Before we are starting the design of staircase, we'll understand why stair design is important:

They should be designed comfortable to use
They provides vertical movement between floors
Must safely carry human loads
They must meet structural safety requirements, etc.

When you poorly stair design, they can cause accidents or structural failure.

II. Decision to Choose the Type of Staircases

First, You have to select the type of stairs type building layout or It's provided by Architectural Plan. The straight or dog-legged stairs are easiest to design. The below are the common type of staircase:

III. Basic Information

You need the following information before design:

Floor-to-floor height
Usage (residential or commercial)
Available stair area
Type of material (RCC, steel, wood), etc.

Example:

Floor height = 3.0 m

Stair width = 1.0 m

IV. Rise and Tread Size

Rise and tread decide stair comfort.
Standard guidelines:
Rise: 150 mm to 180 mm
Tread: 250 mm to 300 mm

Comfort formula:

2 × Rise + Tread = 600 mm (approx.)

V. Choose Stair Slab Thickness

For RCC stairs the typical waist slab thickness around150 mm to 180 mm.

Thickness depends on:

VI. Calculation the Loads on Stair

Types of loads:

Dead load, DL (self weight of concrete)
Live load, LL (people using stairs)
Finishing load (tiles, railing, plaster)

Typical values:

Concrete weight ≈ 25 kN/m³
Live load (residential) ≈ 3 kN/m²
Total load = Dead load + Live load + Finish load

VII. Design of Stair Slab

The stair slab is designed like a simply supported or continuous slab.

Main steps:

Calculate bending moment
Calculate required steel area
Select reinforcement (X-Direction and Y-Direction at the Top and Bottom)

Steel bars are placed:

Along the slope (main reinforcement)
Across the width (distribution steel)

VIII. Reinforcements Detailing of Staircase

Typical reinforcement:

Bar diameter usually 8 mm to 12 mm (According to designers)
Main bars at bottom for simply supported stairs
Certified anchorage into landing beams (Crank/Top Bars)

Good detailing ensures durability and safety for long time.

IX. Final Stair Drawing before Constructions

Final drawing should include:

This drawing is used for construction on site.

Stair Rebar

X. Example

The below is the calculation note of Staircase Design:

Stair Rebar Detailing