The primary difference between a girt and a purlin lies in their function and location within a building structure. Purlins are structural members used on roofs, while girts are used on walls.
Based on the provided reference:
- Roof purlins are used to support metal roofing panels.
- Wall girts are used for the fastening of metal siding.
Both are essential components in metal building construction, but they serve distinct purposes related to different parts of the building envelope.
Understanding Their Roles
Let's break down the specific functions of each element as outlined in the reference.
Purlins: Supporting the Roof
Purlins are horizontal beams or channels that span between the main structural frames of a building, running parallel to the eave. As the reference states, their key role is to support metal roofing panels. The roofing material is fastened directly to the purlins, transferring the roof load back to the main structural system (like rafters or trusses).
- Location: Roof
- Function: Support roof cladding (specifically metal roofing panels per the reference)
- Span: Typically runs horizontally, perpendicular to roof rafters/trusses
Girts: Supporting the Walls
Girts, on the other hand, are structural members used in the wall system of a building. The reference clarifies that wall girts are used for the fastening of metal siding. Similar to purlins on the roof, girts provide the attachment points for the exterior wall cladding. They are typically oriented horizontally between wall columns.
- Location: Walls
- Function: Provide fastening points for wall cladding (specifically metal siding per the reference)
- Span: Typically runs horizontally, perpendicular to wall columns
Comparing Girts and Purlins
Here's a simple comparison based directly on the information provided:
| Feature | Purlin | Girt |
|---|---|---|
| Location | Roof | Wall |
| Function | Support metal roofing panels | Used for the fastening of metal siding |
| Materials | Available in stainless steel or galvanized, can be prime painted and/or coated in ZAM | Available in stainless steel or galvanized, can be prime painted and/or coated in ZAM |
Note: The reference indicates that both girts and purlins can share similar material options, including stainless steel, galvanized finishes, prime paint, and ZAM coatings.
Practical Insight
In essence, think of purlins as the "horizontal roof supports" and girts as the "horizontal wall supports" in a framed structure, specifically designed to carry and transfer the loads from the exterior cladding (roofing and siding) back to the building's main frame. They are often made from similar roll-formed steel sections, but their placement and the specific type of cladding they support define their name and primary purpose.
Building Component Examples (Note: This is a hypothetical link for formatting demonstration)
Understanding the distinction between these two components is crucial in structural design and construction, ensuring that the correct members are used in the appropriate locations to support the building envelope effectively.
