Sheathing Alternatives to OSB and Plywood May Be Worth Considering
As home builders confront sky-high prices for oriented strand board (OSB) and plywood and an uncertain supply of these mainstay construction materials, Toolbase Technotes from the NAHB Research Center are advising the industry that this could be a good time to consider alternative sheathing products.
The alternatives include:
- Imported OSB and Plywood. Other than Canada, U.S. plywood imports come primarily from Brazil and Chile. Some products are distributed from Poland, Germany and France, but their prices may mirror domestic panel prices when shipping costs are added. These products include Radiata pine and Kronopoly OSB, Triply OSB and Masisa OSB. They should have appropriate grade stamps or structural certifications if they are intended as structural sheathing.
- Fiberboard. Known commonly as blackboard, grayboard or buffaloboard, this is constructed of wood compressed with other materials and is used primarily for wall sheathing and floor underlayment. It can be made of recycled fiber, has a higher R-value than most wood-based sheathings, has sound attenuating properties and is less expensive than other wood-based sheathings. Products include Stedi-R and Stedi-R Structural from Georgia-Pacific, Buildrite Structural Sheathing by International Buildrite, Temple Fiber Brace by Temple Inland and Celotex Premium Insulating Sheathing by Knight-Celotex.
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- Cementitious Board. Consisting of Portland cement reinforced with fiberglass mesh, this is typically used as a backboard for ceramic tile installations and has been used as exterior sheathing under a stucco cladding. Not structural in nature, buildings sheathed with cement board must have corner bracing. Producs include Durock by USG and WonderBoard by Custom Building Products.
- Fiber Cement. A mix of wood fiber and cement, panels come textured or untextured in various siding configurations. Flat panels can be used under stucco, and textured panels can be used as sheathing and cladding. Corner bracing can be required by building codes. Products are marketed under the Hardi-panel or Cemplank brands by James Hardi and WeatherBoard by CertainTeed Corporation.
- Gypsum. Products come in a variety of configurations, including exterior-fated gypsum core with paper faces; gypsum core with glass mat faces; and a core of gypsum, cellulose and perlite with water-resistive faces. Gypsum panels are used under brick veneer and stucco finishes, and they can be used to obtain a fire-rated wall assembly. However, they must be handled carefully. Manufacturers include USG (Fiberock), Georgia-Pacific Corporation (Densglass Gold) and National Gypsum Company (Gold Bond).
- Foil or Paper Faced Insulative Board. This thin sheathing product can be applied in large sheets (up to 80 inches by 16 feet.) These products are structural in nature and less expensive than other sheathing options. Products include EnergyBrace and Thermo-Ply by Ludlow Coated Products and Thermo-Ply by Simplex Products.
- Foam Sheathing. This includes extruded polystyrene, expanded polystyrene and polyisocyanurate; provides the most insulation of all sheathing options; and is not structural in nature.
Whether or not builders find these alternatives a suitable substitute for OSB and plywood can depend upon a number of issues related to their application, their structural limitations and their material characteristics, which can have an impact on thermal and moisture performance, the Research Center says.
Many of the options are applicable only for wall sheathing and many are non-structural in nature, requiring measures to resist shear in walls. Also, non-wood sheathing options do not act as a nail base.
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