Planning a multi-storey building: what changes above four floors

Adding floors is not a simple repeat of the ground floor. The loads at the base multiply, and new rules apply as the building grows taller.

What changes with height

• Foundation: more load needs a larger footing, a raft or piles. Soil testing becomes essential.
• Columns and beams: lower-floor columns grow larger and carry more steel.
• Lateral forces: wind and earthquake matter more, and shear walls or a core may be needed. Bangladesh lies in a seismically active region.
• Lift: usually expected beyond about five or six storeys, and it needs a shaft, machine room and pit.
• Fire safety: more exits, a protected staircase, and water supply for firefighting.
• Approvals: taller buildings face stricter setbacks and review.

Keep the plan repeatable

Repeat the stair, lift and wet areas in the same position on every floor. Stack columns directly. This keeps cost down and the load path simple.

Prepare before you hire

1. Draw each floor and check the stair and lift positions.
2. Decide the roof use: terrace, water tank, stair cover room.
3. Run a rough cost to see whether the budget supports the height.
4. Hire a structural engineer and get a soil test before you finalise.

Use floors in the planner

The PlanCraft 3D planner supports ten or more floors, with a floor selector, copy-floor-up, a roof with a parapet and stair cover room, and a cost estimate that switches to a raft foundation and heavier steel as the building rises.

Do not build multi-storey from a planning tool. A licensed structural engineer must design the frame and foundation for the actual soil.

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