Open web trusses for long spans, lightweight framing, and easier MEP integration

When a floor or roof structure needs to clear 40 feet without intermediate columns, solid-sawn lumber and wide-flange steel beams both hit the same constraint: weight. A W18 steel beam spanning that distance adds substantial self-weight before supporting a single square foot of live load. Open web trusses take a different approach, replacing solid cross-sections with a triangulated framework of chords and diagonal members that delivers comparable strength at 40 to 60 percent less mass. Manufacturers such as RedBuilt engineered wood products have refined these systems over decades, producing trusses that handle long spans while leaving open cavities for ductwork, plumbing, and electrical routing.

The global open web steel joist market reached $5.2 billion in 2023 and is projected to hit $8.1 billion by 2032, growing at a 4.8 percent compound annual rate. US truss sales alone accounted for roughly $6.36 billion in 2024. That growth tracks closely with a construction industry spending $2.19 trillion annualized in early 2026, where architects and engineers consistently choose trusses to reduce material costs and simplify mechanical coordination.

How the triangulated web carries load

Every open web truss works on the same structural principle: a top chord, a bottom chord, and diagonal web members arranged in a repeating pattern of triangles. When a distributed load presses down on the top chord, the geometry channels forces through two distinct paths. The top chord goes into compression, resisting the tendency to buckle under the weight above. The bottom chord goes into tension, pulling against the bearing points to prevent the assembly from sagging. Diagonal web members alternate between tension and compression depending on their orientation and the load pattern.

This triangulated geometry gives each truss high stability relative to its weight. A solid beam resists bending through the sheer mass of its cross-section. A truss achieves similar resistance by directing forces along linear members where material works hardest. The open spaces between diagonals are not wasted area. They are the reason the structure can span farther without packing on dead weight.

Engineering the chord sizes and web member angles for a specific span and load case is standard practice now. Most design work happens in software that models deflection limits, connection capacities, and lateral bracing requirements before a single piece of steel or wood gets cut.

Spanning farther with less material

Open web trusses typically span 16 to 60 feet, covering the range that dominates commercial, institutional, and multi-family residential construction. At the shorter end, they compete with solid-sawn joists and engineered I-joists. At the longer end, they replace heavy steel beams and built-up girders that would otherwise demand cranes and larger foundations.

The lightweight nature of these trusses cascades through the rest of the building. Lighter floor and roof framing means smaller columns, reduced foundation loads, and less concrete below grade. A structure framed with open web trusses can weigh 40 to 60 percent less than one using equivalent solid-section beams for the same span and load capacity. That weight savings feeds directly into lower material costs and faster erection schedules.

For roof applications, the depth-to-span ratio of a truss is predictable enough that architects can set ceiling heights and parapet lines early in schematic design without waiting for final structural calculations. Floor trusses follow similar logic, letting the design team lock in floor-to-floor dimensions before the complete engineering package is finished.

Routing MEP systems through the open web

Mechanical, electrical, and plumbing coordination is one of the biggest scheduling headaches in commercial building projects. Solid beams and joists force ductwork and piping to run below the structure, which pushes the ceiling down and increases floor-to-floor height. Open web trusses eliminate this conflict by providing pass-through space within the structural depth itself.

Routing MEP systems through the web openings can reduce floor-to-floor height by 6 to 12 inches per story. In a four-story building, that adds up to two or even four feet of total height savings, cutting exterior cladding costs, shortening vertical runs for plumbing risers and electrical conduit, and sometimes making the difference between fitting four stories under a zoning height limit or settling for three.

BIM coordination between structural and MEP trades has accelerated this advantage. When the truss layout and mechanical routing are modeled together, clash detection happens on screen rather than in the field. This integration shortens the gap between design and manufacturing by 20 to 30 percent on projects that commit to it early.

Steel, wood, and hybrid configurations

Open web trusses come in several material configurations, each suited to different load cases and fire rating requirements.

Steel bar joists use hot-rolled or cold-formed steel for both chords and web members. They dominate warehouse, retail, and industrial roof framing where long spans and durability matter more than fire-rated ceiling assemblies. Standard designations from the Steel Joist Institute cover depths from 8 to 72 inches.

Wood chord trusses pair dimensional lumber or laminated veneer lumber for the top and bottom chords with steel tube or rod diagonals forming the web. This hybrid approach combines the workability of wood with the tension capacity of steel, producing a truss that integrates well with wood-framed bearing walls and accepts standard joist hangers and nailing plates.

The choice between all-steel and hybrid configurations depends on the project’s architecture, fire code requirements, and the trades available on site. Steel bar joists typically need ironworkers. Hybrid wood-and-steel trusses can be handled by framing crews already on the job.

Fabrication speed and jobsite installation

Over 65 percent of new residential builds now use CNC-manufactured trusses, and the commercial sector is trending the same direction. Automated fabrication lines cut, drill, and press metal connector plates with tolerances tight enough that field adjustments are rare. The prefabrication wave, growing at a 6.1 percent compound annual rate through 2028, depends heavily on trusses that arrive at the jobsite ready to set.

Installation speed is where the efficiency gains show up most clearly. A crew of four workers can typically set 20 to 30 trusses per day, covering large floor or roof areas in a fraction of the time required for conventional stick-built framing. Each truss arrives as a single unit, bridging from bearing wall to bearing wall, which cuts the number of individual connections and the labor hours spent measuring and cutting on site.

Temporary bracing during installation is critical. Until sheathing or permanent lateral bracing ties the trusses together, each one is vulnerable to rollover. Bracing sequences are spelled out by the truss manufacturer and should be followed exactly. Skipping steps here risks a progressive collapse that can flatten an entire bay of framing in seconds.

Where open web trusses fit in the broader market

The commercial and industrial sector accounts for roughly 30 to 40 percent of global truss demand, making it the fastest-growing segment. The global roof truss market is projected at $10.57 billion in 2025 with a 5.5 percent CAGR through 2035. Those numbers reflect a construction industry that has moved past treating trusses as a commodity. They are now a design-driven system where span, depth, load capacity, and MEP coordination are all specified together from the earliest project phases.

Prefabricated trusses also align with the broader push toward modular construction. Whole floor cassettes or roof panels can be assembled in a controlled factory environment, shipped flat, and craned into position. This support for off-site assembly reduces weather delays, improves quality control, and compresses project timelines in ways that conventional framing cannot match.

For any building where long clear spans, lightweight framing, or mechanical coordination matters, open web trusses remain one of the most practical choices in the structural toolkit.