In facade construction, performance is only as strong as the details. While much attention is rightly given to insulation and cladding systems, it’s the way external sheathing boards are joined, fixed, and sealed that can determine long-term durability and compliance.
Incorrect edge detailing can lead to water ingress, air leakage, and even compromise fire performance. At Klasse, we offer a complete system of accessories designed to ensure every board edge is secure, sealed, and built to last, including dedicated fasteners, high-performance sealants, and airtight tapes.
Managing Gaps, Deflection and Movement
Movement is inevitable in any external wall build-up, particularly when working with light-gauge steel framing. Vertical movement is typically accommodated through a deflection head detail, allowing the main structure to deflect independently of the wall studs.
LGSF systems are also subject to horizontal deflection, but this is limited depending on the wall finish. For example, SCI P402 recommends a deflection limit of height divided by 250 (H/250) for board or rendered finishes. Klasse sheathing boards, once installed, contribute stiffness that helps reduce overall deflection.
While deflection calculations often assess a single stud under load, actual wind load is distributed across multiple studs and over the board layer. This distribution reduces the risk of differential movement between adjacent studs, especially when detailing is correctly managed.
FireFend Sealant
For builds requiring high-performance joint sealing and fire protection, Klasse FireFend Sealant is a reliable option. Available in Acrylic and Silicone variants, both provide excellent long-term flexibility and protection.
FireFend Silicone offers a design life of over 20 years, a service temperature range of -30°C to +150°C, and can accommodate 25 percent movement (0.75mm to 1.5mm allowance in our minimum & maximum board joint widths).
FireFend Acrylic also offers a 20-year design life, with a temperature range of -10°C to +70°C and 12.5 percent movement accommodation (0.375mm to 0.75mm joint width allowance in our minimum & maximum board joint widths).
Both options are equally suited to sealing board joints. The choice typically depends on the installer's preference or compatibility with surrounding components.
Airtight Tape
Klasse Airtight Tape is a high-tack, flexible sealing solution for use in airtight or vapour-controlled wall systems. With a 20-year design life, a wide temperature range (-30°C to +100°C), and 300 percent elongation, it provides long-lasting performance across both lateral and vertical movement.
Airtight Tape can be used in conjunction with Klasse FireFend Acrylic as a belt-and-braces solution, provided it is applied to dry surfaces and as per guidance. It is not suitable over Silicone sealant unless a suitable primer is used.
Fastening with Confidence
Every secure sheathing board installation starts with the right fixings. Klasse Sheathing Board Fasteners, available for both G-board and C-board variants, are corrosion-resistant and deliver high pull-out performance under load.
Correct placement - including spacing, fixing depth, and edge distance - helps prevent board stress fractures and ensures consistent performance in wind and weather.
Getting the Details Right
Edge detailing is not just a finishing step - it’s fundamental to system performance. Klasse’s accessories are designed to work together to help manage movement, ensure airtightness, and maintain compliance across the external envelope.
From initial enquiry to installation, Klasse provides comprehensive project support tailored to your build. Get in touch today to speak with one of our building envelope experts.
