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What are wood trusses? Wood trusses are engineered structural frameworks made from dimensional lumber, designed to support key parts of a building such as roofs, ceilings, and floors. They are typically built from triangular units connected with wood or metal gussets, creating a strong, stable framework that uses materials efficiently.
Because of their strength-to-weight ratio and efficient use of lumber, prefabricated wood trusses have dramatically lowered the cost of both roof and floor systems in residential and light commercial construction. A major advantage is their ability to distribute loads evenly to the supporting walls and foundation, helping the structure resist wind, snow, dead loads, and live loads over the life of the building.
Modern roof and floor trusses are usually manufactured off-site in a dry, controlled environment. Each truss is designed with specialized software to meet specific span, load, and code requirements, then assembled with construction grade spruce or similar structural softwoods. Once delivered to the building site, the trusses are craned or lifted into place and braced according to the engineer’s layout, allowing crews to frame large areas quickly and accurately.
Truss systems can be customized to accommodate vaulted ceilings, complex rooflines, bonus rooms, and long clear spans. This combination of design flexibility, speed of installation, and material efficiency is why wood trusses remain the cost-effective choice for most new wood-frame construction.
Roof trusses are the primary structural support for the roof system in modern wood-frame buildings. Each truss is a carefully engineered assembly of top chords, bottom chords, and internal webs that work together to carry the weight of the roof sheathing, roofing material, and environmental loads (snow, wind, and maintenance loads). The forces are then transferred down through the walls and into the foundation.
Prefabricated roof trusses can be designed for a wide variety of roof pitches and styles, from simple gable roofs to complex hip, mansard, or gambrel forms. They can also be configured with raised heels to improve attic insulation depth, or with open webs to make routing ductwork and ventilation easier. When properly installed and braced, a roof truss system provides decades of reliable performance with minimal maintenance.
Floor trusses are engineered to support the live and dead loads of floors, especially in multi-story homes and commercial buildings where long, open spans are desired. Unlike conventional solid-sawn joists, open-web floor trusses use a web of diagonal and vertical members to create a lightweight, rigid framework.
This flat truss design allows floor systems to span longer distances without the need for intermediate beams or support columns, making it easier to create open-concept interiors and flexible floor plans. The open web spaces also provide convenient pathways for HVAC ducts, plumbing lines, and electrical wiring, reducing drilling and notching while helping maintain structural integrity. A well-designed floor truss system can reduce squeaks, limit deflection, and deliver a solid feel underfoot.
The king post truss is one of the simplest and oldest wood truss designs. It is characterized by a single central vertical member (the king post) that ties the apex of the rafters to the bottom tie beam. Two inclined rafters extend from the top of the king post down to the bearing points at the walls.
Because of its straightforward layout and minimal lumber requirements, the king post truss is commonly used in small spans such as porches, sheds, garages, and simple residential roof systems. It is also popular in exposed timber frame designs where the truss becomes a visible architectural feature.
The queen post truss is similar to a king post truss but uses two vertical members (queen posts) instead of one. These posts support the tie beam and rafters, allowing the truss to span wider distances than the king post version while still maintaining a relatively simple geometry.
Queen post trusses are frequently used in larger residential roofs, barns, and light commercial buildings, especially where a traditional exposed timber look is desired. The additional vertical support makes them suitable for moderate spans while keeping material usage efficient.
The Fink truss is one of the most widely used roof truss types in residential construction. Its characteristic “W” pattern of internal webs creates a series of triangles that efficiently carry loads from the top chords down to the supports. This repeated triangular geometry delivers an excellent strength-to-weight ratio.
Fink trusses are ideal for standard gable roofs and can be designed for many span lengths and pitches. They are cost-effective to fabricate, fast to install, and capable of supporting significant snow and wind loads, which is why they remain the default choice for many house builders and truss manufacturers.
The Howe truss looks similar to a Fink truss but reverses the orientation of some diagonal web members. In a classic Howe configuration, vertical members are in tension and diagonals are in compression. This arrangement provides excellent stability for longer spans and heavier loads.
Howe trusses are often used in longer roof spans, covered bridges, and industrial buildings where a robust, time-tested truss form is required. They offer a good balance between material efficiency, strength, and ease of fabrication.
The Pratt truss is characterized by its diagonal members sloping toward the center of the span, with diagonals typically in tension and vertical members in compression. This configuration allows the truss to handle substantial loads while minimizing the amount of material needed in compression members.
Pratt trusses are widely used in bridges, industrial roofs, and long-span structures where heavy loads, moving equipment, or traffic are expected. The clear force paths make it easier for engineers to analyze and size members correctly, resulting in a strong, dependable framework.
A scissor truss is easily recognized by its sloping bottom chords that cross or “scissor” at the center of the truss. This design creates a vaulted interior ceiling while still supporting the roof above, making it a favorite choice for great rooms, churches, and open-plan living spaces.
Scissor trusses allow designers to achieve cathedral ceilings without resorting to heavy timber framing or complex structural steel. When properly engineered and braced, they provide a dramatic interior volume while still maintaining good structural performance under wind and snow loads.
The gambrel truss is most often associated with classic barn roofs. It features two different slopes on each side: a steeper lower slope and a shallower upper slope. This creates a distinctive profile that increases usable headroom in the upper story or loft.
Gambrel trusses are well suited to barns, agricultural buildings, and garage-with-loft designs where extra storage or living space under the roof is important. The profile also sheds rain and snow effectively, making it practical for regions with significant precipitation.
Attic trusses are designed to create a usable room or storage area within the roof structure itself. They feature a built-in “room” shape inside the truss, often with a raised bottom chord or special web configuration to provide sufficient headroom.
This design turns what would normally be wasted attic volume into a bonus room, home office, or storage loft, without significantly changing the building footprint. Attic trusses are a smart option when homeowners want additional space but local zoning, setbacks, or budget considerations make full additions impractical.
A mono truss spans a single slope of a roof and is commonly used for shed roofs, lean-tos, additions, and stepped rooflines. Mono trusses can also be paired with standard gable trusses to create interesting multi-level roof designs.
Fan trusses use diagonal web members radiating from or toward a central area, creating a fan-like pattern. They are often chosen where both aesthetics and structural efficiency matter, adding a distinctive look to exposed roof systems in public or recreational buildings.
Northlight trusses are associated with industrial or warehouse roofs that incorporate north-facing clerestory windows or skylights. The stepped or sawtooth profile allows consistent, diffuse daylight to flood the interior without excessive heat gain from direct sun, reducing the need for artificial lighting during the day.
The bowstring truss features a curved top chord that resembles a drawn bow. This shape allows the truss to span very wide distances while providing a clear, open area below with no interior columns. Bowstring roof trusses are well suited to gymnasiums, arenas, aircraft hangars, skating rinks, and large industrial spaces.
The curved form helps distribute loads evenly along the arch, efficiently managing heavy rain or snow accumulation. Architecturally, bowstring trusses add a graceful, sweeping profile that enhances the visual impact of large buildings while keeping the structural system relatively lightweight and cost-effective for the spans achieved.
The Warren truss uses a repeating pattern of equilateral triangles formed by diagonal members. This simple geometry distributes loads efficiently and provides a high degree of rigidity, making Warren trusses common in both roof and bridge applications where uniform loading is expected.
Polynesian trusses incorporate curved or splayed members that echo traditional island architecture. They are often used in resort buildings, pavilions, and outdoor structures where a distinctive tropical or coastal aesthetic is desired.
Mansard trusses are designed for mansard roofs, which feature two slopes on each side—a steep lower slope and a shallow upper slope. This configuration increases usable space in the upper story and allows for dormers and living areas to be integrated into the roofline.
Flat trusses are used for low-slope or flat roofs. They provide a clean, horizontal structure that can support membrane roofing, rooftop equipment, or vegetated “green” roofs. Flat trusses are common in modern commercial and contemporary residential designs.
Triple Fink trusses build on the standard Fink pattern with an additional set of internal webs for extra strength and stiffness. They are used where longer spans or heavier loads demand a more robust version of the classic Fink layout, such as in some commercial roofs and wide residential spans.
In all of these applications, properly engineered wood trusses provide a cost-effective, lightweight, and versatile structural system. Whether you are framing a small residential roof, a multi-story building, or a wide-span recreational facility, there is a wood truss configuration that can be tailored to your project’s span, load, and architectural requirements.
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