In building construction, a stair is more than just a means to move from one floor to another—it is also an important architectural element. While most people notice the treads and risers, one essential part often goes unnoticed—the staircase stringer.
A staircase stringer is a structural component that supports the treads and risers of a stair. It plays a vital role in ensuring safety, stability, and strength. Choosing the right type of stringer is crucial for any construction project, whether it is a residential building, commercial property, or public infrastructure.
In this blog, we will explore the different types of staircase stringers, how they are used in construction, and the relevant IS codes applicable in India.
What is a Staircase Stringer?
A stair stringer is the inclined part of a staircase that holds the weight of the steps and transfers the load to the ground or structural frame. There are generally two or three stringers in a staircase—one on each side and sometimes one in the middle for extra support.
Types of Staircase Stringers
Here are the most common types of stair stringers used in Indian construction:
1. Closed Stringer (Housed Stringer)
In this type, the treads and risers are fixed into the stringer, and their sides are not visible. It provides a clean and enclosed appearance.
Best for: Residential buildings, indoor stairs.
Example: Marble-clad stairs in bungalows.
2. Open Stringer
In an open stringer, the treads and risers are clearly visible from the side, and the top edge of the stringer is cut to fit the profile of the steps.
Best for: Decorative stairs in showrooms or offices.
Example: Mild steel staircases in corporate offices.
3. Mono Stringer
This type uses a single central stringer that supports the steps from the middle, giving a modern and floating appearance.
Best for: Luxury homes or architectural highlights.
Example: Floating wooden stairs in duplex apartments.
4. Double Stringer
Two stringers are placed on each side of the stair, giving it strength and a symmetrical appearance. It’s the most commonly used type.
Best for: General residential and commercial use.
Example: Concrete stairs in apartment buildings.
5. Cut Stringer (Sawtooth Stringer)
These stringers are cut in a zigzag shape to support the steps from underneath, leaving them exposed from the side.
Best for: Aesthetic appeal in modern constructions.
Example: Fabricated steel staircases in malls.
6. Centre Beam Stringer
Also known as spine stringers, these are placed directly under the centre of the steps and are ideal for wide or curved stairs.
Best for: Spiral stairs or custom designs.
Example: Spiral stairs in art galleries.
Material Used for Stair Stringers
- Concrete: Suitable for permanent and strong stairs.
- Mild Steel: Preferred for industrial and modern designs.
- Timber/Wood: Used in decorative stair constructions.
- Aluminium: Lightweight option for temporary or modular setups.
Stringer Height Calculation
The height of a stringer depends on the floor-to-floor height (total rise). Here’s how to estimate: 👉 Formula:
Height of Stringer (Total Rise) = Number of Steps × Rise per Step Height of Stringer (Total Rise)=Number of Steps×Rise per Step
👉 Example:
Floor Height = 2.8 metres Rise per step = 0.175 metres (175 mm) Number of steps = 2.8 0.175 = 16 Number of steps= 0.175 2.8 =16
So, the stringer height (or total rise) = 2.8 m Horizontal run (tread × number of steps) = 0.25 × 16 = 4.0 m
Stringer Width and Thickness
| Material | Width (mm) | Thickness (mm) | Notes |
|---|---|---|---|
| RCC | 200–300 | 150–200 | With reinforcement |
| Mild Steel | 150–200 | 10–16 | MS channel or flat |
| Timber | 250–300 | 50–75 | Used in traditional homes |
Stringer Spacing (in Double or Multiple Stringers)
Residential: Two stringers spaced 900 mm–1200 mm apart
Commercial: Additional centre stringer if width > 1500 mm
Open Stringer: Often custom cut with tread slots 250–300 mm apart
Factors to Consider When Choosing a Staircase Stringer
- Load-bearing capacity
- Aesthetic requirement
- Budget
- Maintenance
- Space availability
IS Codes for Stair Construction
When designing and constructing stairs and stringers, the following Indian Standards (IS codes) should be referred:
- IS 456: 2000 – Code of Practice for Plain and Reinforced Concrete
- IS 875 (Part 1 & 2): 1987 – Dead and Live Loads on Buildings
- IS 962: 1989 – Code of Practice for Architectural and Building Drawings
- IS 1905: 1987 – Code of Practice for Structural Use of Unreinforced Masonry
- NBC 2016 – Part 4 – Fire and Life Safety Guidelines for Staircases
Download our IS code App for all kinds of Is codes in Civil engineering.
Real-Life Example in India
In modern Indian flats, stairs with closed stringers and concrete structure are often used due to durability and fire resistance. In contrast, in villas or luxury houses, mono stringers with timber treads are used to add a premium look.
Summary Table: Types of Staircase Stringers
| Type of Stringer | Visibility | Suitable for | Material Commonly Used | Example Use Case |
|---|---|---|---|---|
| Closed Stringer | Hidden | Homes, apartments | Concrete, Timber | Indoor stair in flats |
| Open Stringer | Exposed | Offices, showrooms | Steel, Timber | Decorative stair in retail shops |
| Mono Stringer | Central | Luxury homes | Steel, Wood | Floating stair in duplex houses |
| Double Stringer | Side-mounted | General use | Concrete, Steel | Apartments, schools |
| Cut Stringer | Zigzag shape | Aesthetic appeal | Steel, Wood | Modern stair in shopping malls |
| Centre Beam Stringer | Middle support | Spiral/custom stairs | Steel | Spiral stair in showrooms |
Conclusion🎯
Understanding the types of staircase stringers helps in making informed decisions during the planning and design phase of a stair. For Indian construction, it’s essential to balance strength, cost, and aesthetics. Always consult a structural engineer and refer to relevant IS codes to ensure safety and compliance.