Introduction

Joinery methods of Z-shaped sub-framing can play a major role in the structural integrity of a building. There are several different joinery methods that can be used, and all have advantages and disadvantages.

Z-girts are typically manufactured in standard lengths, such as 8′. This is necessary for installation purposes, as one person can typically install an 8′ girt alone. This can affect project plans, as most wall lengths are more than 8′ in length.

Join the ends of girts to create continuity along the wall. Consider these critical engineering metrics for these end conditions:

• Structural stress and deformation analysis
• Attachment detail to the substrate
• Allowance for thermal expansion along the length of the girt

The most common wall configuration includes the horizontal installation of Z-girts over vertical studs. Structural calculations require the lateral joinery detail for the horizontal installation of Z-girts over vertical studs. The following covers the most common joinery techniques for girts.

Lap Joints with Traditional Metal Z-Girts

Traditionally, steel Z-girts are made of relatively thin metal (i.e., 0.062″) with a high value of elasticity and stiffness. This allows them to easily lap and stitch together with a lap joint method. The basic lap joint consists of two overlapping members that are connected with screws or rivets.

This type of joinery is often used for metal z-girts due to the relatively thin material. The overlapping members create an interlocking connection that helps to distribute forces over a larger area than a single fastener could. This helps to reduce the risk of failure or buckling of the joint under high-load-bearing applications.

When using metal Z-girts, ensure that the lap joint is properly installed. Avoid fastening at all lap joints to allow for thermal expansion. Also, check that the overlapping pieces align correctly, as misalignment can create weak points in the joint.

Composite or fiber-reinforced polymer (FRP) Z-girts, being thicker than steel girts, make lap joint methods challenging. When attempted with thicker girts, it creates out-of-plane offsets in the wall’s vertical plane.

Lap Joint Method for Steel Z-Girts

Butt Joints with Standard Fiber-Reinforced Polymer (FRP) Z-Girts

A butt joint forms when you join two pieces of material end-to-end with no overlap. Butt joints place each Z-girt end on half of a stud. This joinery method is unacceptable on a single stud for best practice considerations due to a minimum required margin space of 2.5 fastener diameters at the end of girt for FRP (0.25″ fastener diameter x 2.5 required margin space + 0.25 “fastener + 0.1875″ metal edge margin x 2 sides = minimum flange width of 2.125”).

To effectively use butt joints with FRP girts, you need double studs at every FRP girt joint, which increases material and labor costs.

Butt Joint Method for Fiber-Reinforced Polymer (FRP) Z-Girts

Cantilever Joints with Standard Fiber-Reinforced Polymer (FRP) Z-Girts

The cantilever joinery method involves installing girts horizontally with a cantilever over the studs on both ends. While cantilevering Z-girts can provide a quick and easy joint, it does not provide the same level of security or integrity that other joinery methods provide. Cantilevering Z-girts leaves part of the girt unsupported, causing it to sag or become misaligned over time. This situation can compromise the structure’s overall integrity and pose safety risks if the girts lack proper securement.

Although cantilevering Z-girts might be feasible in some situations, avoid it whenever possible, as it is not best practice.

Use the maximum possible cantilever for the worst typical case in structural calculations (e.g., 15″ for a 16″ O.C. stud).

Cantilever Joint Method for FRP Z-Shaped Girt

Interlocking Joints with GreenGirt CMH™ Z-Girts

Benefits of Interlocking Joints

Interlocking joints with GreenGirt CMH Z-girts, comprised of a composite metal hybrid material, is the best practice for providing a reliable connection between two Z-girts. The GreenGirt CMH™ Z- girt has an integral interlocking system that enables one end of a girt to connect to the adjacent girt. This type of joint eliminates the need for Z-girt ends to align and fasten at studs, which can reduce construction time and cost.

Structural Advantages

Interlocking joints are also structurally sound and provide greater strength compared to lap joints, butt joints, and cantilevers. The patented interlocking design of the GreenGirt CMH™ Z-girt allows for ease of connection and installation of the Z-shaped girt while providing best practice structural integrity.

Interlocking Joint Method for GreenGirt CMH Z-Girts

When selecting Z-girts with various joinery methods, it is critical to factor in real-life installation scenarios and the application of the joint type. Proper joinery for Z-girts ensures that the structure remains safe and secure and that the connection between the girts and framing members is robust. Failure to implement appropriate joinery methods can compromise the structural integrity of the building.

Advanced Architectural Products Solutions

At Advanced Architectural Products, creators of GreenGirt CMH Z-girts, we provide industry-leading solutions for continuous insulation and building enclosure systems. Our GreenGirt CMH Z-girts are integral to both GreenGirt CMH continuous insulation and the SMARTci building enclosure systems. These innovative solutions offer a thermal break and a structural mounting platform, ensuring universal compatibility with any substrate, insulation, or cladding.

Superior Performance and Durability

Designed to eliminate thermal gaps and cracks that other systems may overlook, the GreenGirt CMH Z-girt specifically provides a best-in-class continuous insulation and building enclosure sub-framing solution. The composite metal hybrid technology combines the thermal benefits of FRP and the structural strength of steel, delivering superior overall performance. GreenGirt CMH Z-girts offer the same load-bearing capacity as equivalent-depth steel Z-girts while also being corrosion-resistant, making them a highly durable and efficient choice for modern construction.

Contact an A2P Representative to learn more about GreenGirt CMH Z-girts, GreenGirt CMH continuous insulation, or SMARTci building enclosure systems today.

© 2023 Advanced Architectural Products