01/04/2026
In the Bangladesh National Building Code, there is no direct term called “stair-to-stair distance” like in some international codes. However, the concept you’re asking about is covered under exit separation / location of stairways (means of egress).
🔑 BNBC Rule for Stair-to-Stair Distance (Exit Separation)
When two or more staircases (exits) are required in a building:
👉 Minimum distance between stairs =
At least ½ (one-half) of the maximum diagonal dimension of the building or floor area served
📌 From BNBC:
“Exits … shall be located at a distance from one another not less than one-half of the length of the maximum overall diagonal dimension of the building or area served.”
📐 Simple Explanation
If your building floor is rectangular:
Calculate the diagonal length (D) of the floor.
Required distance between two stairs =
👉 D / 2 (minimum)
📊 Example
Building size = 20 m × 30 m
Diagonal = √(20² + 30²) = 36 m (approx.)
Minimum stair-to-stair distance =
👉 36 / 2 = 18 m
✔ So, the two stairs must be at least 18 m apart
⚠️ Important Notes
This rule applies when:
More than one exit stair is required (e.g., high-rise, large occupancy)
Purpose:
Ensure alternative escape routes
Prevent both stairs being blocked by the same fire/smoke source
🧱 Additional BNBC Stair Location Guidelines
Minimum two staircases for many buildings (especially high-rise)
Stairs should be:
Located remotely from each other
Easily accessible from all parts of the floor
Often placed:
At opposite ends of the building (best practice)
✅ Summary
BNBC does not say “stair-to-stair distance” explicitly
But uses exit separation rule:
Distance ≥ ½ of building diagonal
If you want, I can also show:
BNBC diagram for stair separation
Differences with IBC/NFPA rules
Viva/interview short answer version
