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Structuralaka: horizontal forceaka: lateral load

Lateral Force

In Plain English

Any horizontal force—from wind, earthquakes, or soil pressure—that pushes sideways on a structure.

Definition

A horizontal force acting on a structure caused by wind pressure, earthquake ground motion, soil or hydrostatic pressure, or other horizontal loads. Lateral forces must be resisted by the building's lateral force-resisting system, which may include shear walls, braced frames, or moment frames. Building codes specify minimum lateral force requirements based on location, building height, and occupancy.

Why It Matters in Bidding

Lateral force requirements determine the size and cost of shear walls, braced frames, holdowns, and connections, which can be a significant share of the structural bid in high-wind or seismic regions. Estimators must read the structural drawings carefully, since under-pricing the lateral system or missing specialty hardware is a common source of bid busts and change orders.

Example

An estimator in a high-seismic zone adds cost for additional holdowns and thickened shear-wall sheathing after the structural engineer increases the lateral force demand on the design.

Related Terms

Wind LoadSeismic DesignShear WallBracing

Frequently Asked Questions

Lateral force is carried by the lateral force-resisting system, typically shear walls, braced frames, or moment frames, working together with floor and roof diaphragms that collect the load and deliver it to those vertical elements. Holdowns, anchor bolts, and connection hardware tie the system to the foundation and are easy to underbid.
Codes set lateral demand from site-specific wind speed and seismic ground-motion data, so an identical building costs more to brace in a coastal hurricane zone or high-seismic region than inland. Estimators should confirm the design loads on the structural sheets, because higher demand means more steel, hardware, and labor in the bid.
Gravity loads act vertically downward, the building's weight plus occupancy and snow, and are carried by columns, beams, and footings. Lateral force acts horizontally from wind, earthquakes, or soil and must be resisted by a separate bracing system. Both must be priced, and the lateral system is often the one estimators overlook.

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