Alternative Construction Research Guide - GCCDS

Sheathing | 7.2PERFORMANCEWind Load: Sheathing is nailed to stud walls, creating astructural diaphragm that resists horizontal forces againstthe wall. It is affixed to the studs with a prescribed nailpattern engineered to withstand wind forces appropriateto the region, and should be carefully monitored to ensureproper installation.Water Resistance: Wood sheathing is prone to rot andmold and should be kept dry on site and inspected before (Fig. 13) When not using full-height sheathing, panels should be properlyspaced and overlapped, and affixed according to specified nailinguse to ensure quality.patterns.Energy / Thermal: Sheathing itself has low thermalresistance. However, it can be a large determining factorin how the wall performs, based on proper installation andsealing of seams, and depending on the material used.Common Failure: Failure in sheathing may result fromimproper nailing in the case of a high wind event. Morelikely is rot or decay from excessive moisture due to leaksin the building envelope. This can be prevented by properlysealing panel systems per manufacturer specification,as well as the proper application and installation of housewrap in the case of a conventionally sheathed OSB orplywood wall. 13(Fig. 14) Full-height sheathing can increase the shear strength of thewall system.DESIGNEnvironmental Impact: Plywood manufacture usesmore mature wood than OSB or hardboard alternatives.The key to minimizing impact with plywood is to optimizematerial use and reduce waste.OSB, in contrast, is made from short rotation or re-usedchip products, but uses petrochemical binders in itsmanufacturing process. Builders can look for productswith minimal binders and maximum recycled content. 14Versatility / Flexibility: Sheathing is manufactured ina variety of different material compositions and lengthsand provides a wide array of choices for the builder. Increasedlengths allow builders to connect the sill and topplate with one panel, resulting in increased resistance touplift and wind shear. 15(Fig. 15) Properly nailing and wrapping the sheathing with a moisturebarrier is essential to prevent rot and mold in hot and humid climates.