01/12/2025
Kinds of trusses
🏠 UNDERSTANDING ROOF TRUSS TYPES
The image you provided illustrates a variety of common roof truss designs used in building construction. Trusses are engineered frameworks, typically made of wood or metal, used to support a roof, providing structural integrity over long spans.
Here is a detailed description and breakdown of the truss types shown in the photo, categorized by their general shape and structural characteristics:
1. COMMON TRIANGULAR TRUSSES (SYMMETRICAL)
These are the most traditional types, defined by their triangular shape and internal webbing.
• Kingpost: The simplest truss, featuring a central vertical post (the king post) supported by two rafters and a horizontal tie beam.
• Queenpost: Similar to the Kingpost, but uses two vertical posts (queen posts) placed further apart, which allows for longer spans.
• Fink: Characterized by its W-shaped internal webbing. This design is very common and efficient for medium spans.
• Howe: Characterized by a pattern of internal webbing that alternates between vertical members and diagonal members, with the diagonal members generally sloping inward toward the center.
• Fan: A variation with more vertical and diagonal members radiating from the bottom chord (like a fan) to support larger loads or longer spans.
• Modified Queenpost: An enhanced Queenpost design, often including additional vertical and diagonal members in the center section for increased strength or longer spans.
• Double Fink / Double Howe: Used for very long spans. They essentially double the internal webbing pattern (Fink or Howe) to provide more support points across the bottom chord.
2. TRUSSES FOR SPECIFIC CEILING SHAPES
These trusses are designed to create non-flat ceiling planes within the building below.
• Scissors: Designed with bottom chords that slope upwards toward the center, creating a vaulted or cathedral ceiling effect inside the room below.
• Cathedral: A type of truss specifically designed to follow a dramatic, steeply pitched roof and ceiling line.
• Attic: A specialized truss that incorporates an open, usable space in the center, typically for an attic room or storage. The bottom chord is usually deeper to accommodate a floor.
• Gambrel: Features a distinctive top chord with two different slopes on each side (a shallower upper slope and a steeper lower slope), creating the traditional barn-like profile.
3. ASYMMETRICAL AND SPECIALIZED TRUSSES
These designs deviate from the standard symmetrical triangle.
• Monopitch (or Single Pitch): A simple, one-sided triangular shape used for roofs that slope in only one direction, such as on an addition, shed, or certain modern home designs.
• Inverted: The main triangle shape is "inverted" or flipped, often used for specific architectural needs where the peak is lower than the supports.
• Studio: An asymmetrical truss designed for a roof that slopes mainly in one direction but has a slight ridge and smaller slope on the other side.
• Hip: Designed for the end or corner section of a hip roof (a roof that slopes down on all four sides). It has a shorter bottom chord and tapers down in height.
• Piggyback: A small, triangular truss that sits on top of a larger, often flat or low-pitch truss below it. This is used when the overall roof height is too great for a single truss to be manufactured or transported.
• Coffer(ed): Likely refers to a truss with a slight downward curve on the top chord, possibly to create a specific decorative ceiling feature or a slightly bowed roof line.
4. LOW-PROFILE AND FLAT TRUSSES
These are used for roofs that have a very shallow slope or are intentionally flat.
• Flat: Has parallel top and bottom chords, creating a rectangular or square profile. It's used for flat or extremely low-slope roofs.
• Sloping Flat: Similar to a flat truss, but the top chord is slightly angled relative to the bottom chord, providing the minimal slope necessary for drainage on a flat
• Dual Pitch: A flat-like truss where the top chord slopes gently upward from both sides to a low peak in the middle, again to aid drainage.
• Stub: A shorter, often partial truss used in conjunction with other framing members or to bridge small gaps.
In summary, the photo provides an excellent visual dictionary of roof truss geometry, demonstrating how the internal arrangement of wood members (webbing) and the overall shape are tailored to meet different architectural needs, spans, and ceiling designs.
