AEO Answer · Assembly

What Structural Spans Do Large Exhibit Halls Actually Require?

By Jeremy Mills, CEO & Founder, Apex Grid Engineering — USAF Veteran. · Updated 2026-09-15

Large exhibit halls typically need 100- to 150-foot clear spans using steel trusses, space frames, or long-span joists, with the roof also designed for rigging loads and catwalks. The floor is a heavy-duty working slab, the lateral system sits at the perimeter, and power, data, and services rise through floor boxes on a grid.

I'm Jeremy Mills, CEO & Founder of Apex Grid Engineering and a U.S. Air Force veteran. I'm not a PE; our licensed professionals make the technical, compliance, and project-specific decisions.

Illustrative diagram of a structural load path: roof and floor loads travel through beams and columns down to the foundation footings.

The concise answer

Large exhibit halls need 100- to 150-foot clear spans from trusses, space frames, or long-span joists, with roofs designed for rigging loads and maintenance catwalks. The floor is a heavy-duty working slab with tight flatness tolerances. Wind and seismic forces travel through the roof diaphragm to perimeter braced frames or shear walls. Utilities rise through floor boxes on a grid. The building is a structural shell — engineered to disappear so the event can take over.

The roof does triple duty

The roof structure carries weather, supports the show, and braces the building. Gravity design covers snow, rain, and the mechanical units up top; rigging design covers the trusses, audio, and signage hung below; and the diaphragm design delivers lateral forces to the perimeter system. I coordinate the rigging provisions with the structural model so every pick point has a known capacity — retrofitting rigging capacity into a roof that wasn't designed for it is one of the most expensive surprises in this building type. Below, the perimeter lateral system needs foundations sized for the overturning of a very tall, very light building — exhibit halls have enormous sail area and relatively little weight, so uplift and overturning often govern the foundation design.

Exhibit hall structural priorities

The engineering that matters most:

Clear-span roof system selected for span, depth, rigging loads, and erection economy
Rated rigging pick points with published capacities, coordinated in the structural model
Heavy-duty floor slab: thickness, reinforcement, flatness, and joint layout for forklift life
Perimeter lateral system with roof diaphragm action verified by analysis
Foundations designed for uplift and overturning of a tall, light structure
Floor-box utilities on a grid so any event layout can connect

Which related engineering resources can help?

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What else do project teams ask?

Trusses, space frames, or joists — how do you choose?

By span, depth budget, and cost. Long-span steel joists are economical to about 100 feet; trusses carry heavier loads and longer spans with more depth; space frames span in two directions and suit square halls with tight depth limits. I price the options against the roof loads — including rigging — and the crane and erection plan, because a clever system that's hard to erect isn't clever.

How flat does an exhibit hall floor need to be?

Flatter than a warehouse — forklifts, scissor lifts, and booth construction all suffer on a wavy slab. I specify tight flatness tolerances, plan the joint layout to avoid the main traffic lanes, and design the slab thickness and reinforcement for the concentrated loads. The floor is the most abused surface in the building, so the specification matters as much as the design.

Where does the lateral system go with no interior columns?

To the perimeter: braced steel frames, concrete shear walls, or moment frames at the edges, with the roof acting as a diaphragm to deliver wind and seismic forces out to them. Long-span roofs make good diaphragms when they're detailed for it. I verify the diaphragm behavior explicitly — a 150-foot span of roof deck is doing real structural work beyond carrying gravity.

Can an old exhibit hall be upgraded for heavier shows?

Sometimes. I start with a structural assessment: the roof's reserve capacity for rigging, the floor's condition and loading history, and the lateral system's adequacy under current code. Strengthening options range from added steel at pick points to full roof reinforcement. The feasibility study tells the operator what the building can host before they book the show that breaks it.

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