Choosing the right roof truss system is essential for building stability, cost efficiency, and architectural design. Roof trusses are engineered frameworks that provide support for the roof, distributing weight and offering structural integrity. Understanding the different types of roof trusses can help builders, architects, and homeowners make informed decisions. Below is a summary table highlighting key features of 10 common roof truss types used in construction projects across the U.S.
| Type Of Roof Truss | Typical Use | Characteristic Feature | Span Range |
|---|---|---|---|
| King Post Truss | Small residential buildings | Simple triangular design with central vertical post | Up to 20 feet |
| Queen Post Truss | Medium-span roofs | Two vertical posts, allowing longer spans than king post | 20 to 45 feet |
| Fink Truss | Common residential roofs | W tension members form a W shape for strong support | Up to 60 feet |
| Howe Truss | Bridges, warehouses, large buildings | Diagonal members in compression, verticals in tension | Up to 150 feet |
| Pratt Truss | Bridges and long-span roofs | Opposite of Howe truss; diagonals under tension | Up to 150 feet |
| Fan Truss | Wide-span and curved roofs | Multiple rafters spread like a fan | Up to 100 feet |
| Gambrel Truss | Barns, colonial and Dutch-style homes | Two slopes on each side, upper slope is shallower | Varies widely |
| Scissor Truss | Cathedral ceilings and vaulted roofs | Intersecting bottom chords that slope upward | Up to 60 feet |
| Mansard Truss | French-derived architectural styles | Two slopes, upper steep lower shallow for added space | Varies by design |
| Lenticular Truss | Specialized architectural uses, bridges | Lens-shaped with convex top and concave bottom chords | Up to 200 feet |
King Post Truss
The King Post Truss is the simplest type, ideal for small structures like cottages. It consists of a triangular frame with a single central vertical post (the king post) connecting the apex to the base. This design provides basic roof support for spans generally under 20 feet. Its straightforward construction and cost-effectiveness make it popular in light-framed buildings.
Queen Post Truss
Building off the king post design, the Queen Post Truss uses two vertical posts instead of one, allowing greater spans reaching up to 45 feet. This truss can support larger roofs such as those in medium-sized residential and commercial buildings. The space between the posts can be used for additional storage or vaulted ceilings.
Fink Truss
The Fink Truss is the most common modern truss used in residential construction. Its distinctive W-shaped webbing maximizes strength and reduces material needs. This shape allows efficient load distribution and is capable of spanning up to 60 feet. Fink trusses support steep and pitched roofs effectively, making them versatile.
Howe Truss
The Howe Truss is widely used in bridges and heavy commercial buildings where longer spans are needed. It features diagonal members working in compression and vertical members in tension. This configuration provides excellent load-bearing capacity and can span distances exceeding 150 feet, ideal for warehouses or industrial buildings.
Pratt Truss
The Pratt Truss is similar to the Howe truss but with reversed tension and compression roles for the diagonal and vertical members. Diagonals are under tension, making it efficient for long spans and dynamic loads. Pratt trusses are commonly seen in bridges and large roofs where structural efficiency is crucial.
Fan Truss
The Fan Truss includes multiple supporting rafters radiating from a single point, resembling a fan shape. This truss supports wide-span or curved roofs and can span up to 100 feet. The design is suited for auditoriums, gymnasiums, and architectural projects requiring open interior spaces without columns.
Gambrel Truss
Frequently seen on barns and Dutch Colonial homes, the Gambrel Truss provides a distinctive double slope on each side with a shallower upper slope. This design increases usable attic space and improves drainage. Gambrel roofs can accommodate a variety of spans and are valued for their aesthetic and functional flexibility.
Scissor Truss
The Scissor Truss is characterized by two bottom chords that cross or intersect, creating vaulted or cathedral ceilings. It provides **increased interior height** without increasing the roof pitch drastically. These trusses are popular in churches, residential homes, or any structure desiring an open ceiling effect, supporting spans up to 60 feet.
Mansard Truss
Inspired by French architectural styles, the Mansard Truss features a dual-pitched roof with a steep lower slope and a shallower upper slope. This construction maximizes usable attic space and adds a distinctive profile often used in historic and upscale modern buildings. Span limits depend on design complexity and framing materials.
Lenticular Truss
The Lenticular Truss is shaped like a lens, with convex top and concave bottom chords. This unique form provides excellent distribution of forces and aesthetic appeal. Lenticular trusses are often used in special architectural projects, including long-span bridges, where spans can reach up to 200 feet while maintaining light weight and durability.