Glass Mat Gypsum Sheathing has been used on exterior walls for decades and remains a practical, code-recognized substrate for a wide range of cladding materials. Manufactured to ASTM C1177 and referenced by both the International Building Code (IBC) and the International Residential Code (IRC), the panels provide a consistent level of quality, performance, and resilience for projects of all sizes.
The following installation practices, drawn from the GA Residential Design Guide, help builders, contractors, and designers achieve efficient, code-compliant installation.
Tip 1: Handle and store properly to preserve dimensional stability.
Gypsum panels are dimensionally stable, meaning that edges and ends of Glass Mat Gypsum Sheathing do not need to be spaced or gapped as the product does not swell. Proper handling protects this stability. Take care to avoid damaging panel edges in transport. When possible, shield materials from extended exposure prior to installation in order to maintain fit and alignment.
Tip 2: Follow ASTM C1280 or GA-253 for installation and joint practices.
The application techniques for Glass Mat Gypsum Sheathing parallel those for interior wallboard. As such, sheathing must be installed in accordance with ASTM C1280 or GA-253. Panels are fastened with screws or nails driven into framing members. Joint treatment is not routinely required but may be necessary when cladding incorporates an integrated barrier system. In such instances, the panel manufacturer and the barrier system manufacturer should be consulted.
Tip 3: Coordinate the sheathing with the cladding system.
Once installed, Glass Mat Gypsum Sheathing forms a continuous surface suitable for adhesive-attached systems, including EIFS. Mechanically fastened claddings may also be used if cladding fasteners penetrate the framing. Some systems require mastics or sealants at joints, making early coordination with the cladding manufacturer an essential step to avoid field conflicts or rework.
Tip 4: Plan panels so edges align with framing when used in a structural application.
Glass Mat Gypsum Sheathing can be used as an exterior bracing element in Braced Wall Panels (BWP) that are used for structural support. This requires all ends and edges of the sheathing panels to be attached to framing members or blocking. This also helps create a uniform substrate and supports proper fastening throughout the wall system.
Tip 5: Understand structural and code considerations from the outset.
Glass Mat Gypsum Sheathing can contribute to structural performance when used as part of a braced wall panel (BWP). Panels may serve as an exterior bracing element in dwellings built to the IRC, provided the prescriptive requirements for Method GB and related fastening tables are met. When design conditions exceed those provisions, additional engineering or alternative sheathing methods may be needed.
A Successful Installation
By planning layout carefully, preserving material integrity, following application standards, and coordinating with the cladding and structural design, builders can install Glass Mat Gypsum Sheathing efficiently and with confidence.