The thickness of a roof truss primarily refers to the width of the lumber used to construct its components.
Common wood roof trusses are typically constructed with lumber that results in finished thicknesses of 1.5”, 3”, or 4.5” (3.8, 7.6, 11.4 cm).
Common Roof Truss Thicknesses
Based on standard construction practices and materials often used, the thickness of wood roof trusses falls into a few common dimensions. These thicknesses correspond to the dimensions of the wood members (chords and webs) that form the truss structure.
Here are the common thicknesses:
- 1.5 inches (3.8 cm): This is a very common thickness, often corresponding to standard "dimensional lumber" like 2x4 or 2x6 wood members used flatwise in certain applications or for smaller components.
- 3 inches (7.6 cm): This thickness can be achieved by using thicker lumber or by assembling two 1.5-inch members side-by-side.
- 4.5 inches (11.4 cm): Similar to the 3-inch thickness, this is often created by fastening three 1.5-inch members together for increased strength.
| Common Wood Truss Thickness | Equivalent in Inches (") | Equivalent in Centimeters (cm) |
|---|---|---|
| Standard | 1.5 | 3.8 |
| Double | 3.0 | 7.6 |
| Triple | 4.5 | 11.4 |
Note: These thicknesses refer to the material width, not the overall height or depth of the truss.
Understanding Truss Dimensions
It's important to distinguish truss thickness from other dimensions:
- Thickness: The width of the lumber members used to build the truss.
- Depth: The vertical height of the truss, measured from the peak (or top chord) down to the bottom chord at its deepest point. For example, a Sloping Flat Truss, as referenced, can have depths between 24” and 72” (61-183 cm). This dimension is crucial for spanning distances and supporting loads.
- Length (or Span): The horizontal distance the truss covers from one support to the other.
- Pitch: The slope of the top chord, often expressed as a ratio (e.g., 1:1 to 1:6).
The elements that make up the truss structure itself include:
- Chords: The main top and bottom members running the length of the truss.
- Web Members: The diagonal and vertical pieces connecting the top and bottom chords.
- Joints: The points where chords and web members are connected, typically using metal plates (gussets).
While the depth and span are critical for structural performance related to the roof's size and load requirements, the thickness relates directly to the size of the individual wood pieces used to build the truss components.
