Exterior-Wall-Sheathing-Explained

Exterior Wall Sheathing Types & Advantages

Exterior wall sheathing is essential to having strong and durable exterior walls. OSB and plywood are the most common exterior wall sheathing types, increasing structural stability and holding fasteners better than less substantial materials.

For new home construction or replacing siding on an existing home, the outer wall sheathing is a crucial component of the overall exterior facade. 

Exterior Wall Sheathing Explained

Exterior wall sheathing refers to the boards or panels outside a home or building wall between the cladding and the studs. The two basic categories of exterior wall sheathing are structural and non-structural. Both types are offered in many materials and play a vital role in insulating and increasing the strength of exterior walls.

Depending on the age of your home, most exterior walls have 7/16 or 1/2 exterior sheathing, either in the form of plywood, fiberboard, OSB, or wood battens for older homes.

While the standard 1/2 thickness will suffice in most situations, thicker wall sheathing increases nail-holding power and the ability to nail between studs. 

Increased nailing flexibility allows siding installers to fasten between wall studs, making exterior siding flush and even. 

Huber Zip System Wall Sheathing

Huber Zip System is one of the most innovative systems on the market. This system provides a weather-resistant coating to one side of the sheathing, acting as a barrier to lock out moisture.

Huber-Zip-Sheathing-System

The most notable advantage is that it eliminates the need to install housewrap. While expediting the weatherization process reduces labor costs, Huber Zip sheathing has also considered expediting insulating walls.

Zip R Sheathing contains a Poly Iso insulation layer intergraded to the back of each panel. The insulation barrier provides an additional thermal barrier between the exterior wall sheathing and the studs, increasing the effective R-value.

The seams for each system are taped and sealed for a weather and airtight barrier. Unlike older systems, Zip Tape contains an acrylic adhesive instead of previous butyl and asphalt.

Zip is available in two colors: 7/16 OSB is green, while 5/8 and 3/4 OSB are brown. The color variations only distinguish the sizes and are otherwise identical products.

Oriented Stand Board (OSB) Wall Sheathing

OSB is a cost-effective alternative to other costly exterior sheathings. OSB is commonly used in modern home building and framing and meets today’s codes and standards. 

OBS-Plywood-Wall-Sheathing

OSB is processed wood flakes glued with heat and pressed in a cross pattern. The grain orientation of OSB increases its strength, making it stronger than plywood of equal thickness.

Commodity OSBs from manufacturers such as Norboard and LP have a lower moisture resistance. Therefore, these products have installation limitations and require a weather barrier when applied to exterior walls.

Higher grade OSB such as Huber Advantech contains a water-resistant resin that reduces water penetration and increases rigidity. This increased rigidity enhances the shear strength of exterior walls, preventing studs from racking during high-pressure winds and storms.

OSB offers the flexibility of large panels, including standard 4×8 sheets, larger 4×9, 4×10, and custom 8×24 ft sizes. Thickness ranges from 7/16, 15/32, 23/32, and more.

Georgia Pacific Plywood Wall Sheathing

While building material prices have always been volatile, plywood remains the most expensive outside wall sheathing for residential construction. The standalone price of plywood and the necessary weather barrier put this combination outside most siding installation budgets.

Georgia Pacific CDX plywood consists of three Douglas Fur or Yellow Pine veneers. Requiring less glue to form each sheet of plywood makes it more resistant to small amounts of moisture, increasing its durability. Interior grades of plywood are often made from Maple Wood for interior finish work and are not applicable for exterior usage.

Plywood ranges from 1/2 to 1-inch thicknesses, although plywood provides a lower R-value overall than other sheathing options.

Fiberboard Sheathing

Fiberboard, also known as Beaverboard®, blackboard, buffalo board, gray board, or cane board, from manufacturers such as Celotex®, Homasote®, Insulite®, and Nu-Wood, is a recycled alternative wall sheathing used in residential and commercial applications.

Fiberboard-Residential-Commercial-Sheathing

Fiberboard was an industry standard of the 80s. It’s often best practice to replace old fiberboard with rigid wall sheathing, increasing lateral and structural stability. 

Fiberboard is also notorious for accelerated degradation, providing a source for animals and insect nesting. Additionally, fiberboard does not substantiate exterior walls compared to other materials. However, fiberboard has improved over the years and offers the best noise reduction, making it great for apartment and commercial applications.

Foam Board Insulation

In essence, foam board insulation provides the highest R-value of any exterior sheathing, lowering home energy bills. Foil-faced foam board sheathing is most applicable and practical in cooler climates, reaching effective R-values as high as 30 or more.

Foam-Board-Insulation-Panel

While foam board offers insulation properties essential for exterior wall plumbing, open-cell foam is prone to holding water once wet. Therefore, it’s best to seek advice from professionals familiar with each installation’s specifics and use closed-cell foam for exterior applications.

Commonly installed for advanced siding systems and vinyl siding, foamboard insulation does not increase wall strength. Siding installers are also limited to nailing on studs due to the lack of nail-holding power. 

Foamboard is a non-structural exterior sheathing that can be combined with other sheathing and rainscreen systems, providing the best comprehensive sheathing system.

Horizontal Tongue & Grove Wall Sheathing

Tongue and grove wall sheathing is widely a thing of the past. From the mid-1920s to the late 1950s, horizontal and vertical tongue and groove exterior wall sheathing was solely used without combining insulation or other materials. 

Measuring 3/4″ of solid wood, made tongue and grove are the most substantial exterior wood wall sheathing used. Most planks were 4-6 inches wide, which increased time and labor. 

Tongue and groove exterior sheathing is not used in modern building design, and if an older home has it and needs repairing, expect an installation cost of 3-4x more than plywood sheathing.

Gypsum Exterior Sheathing

Gypsum-Extended-Exposure-Sheathing

While not a favorite choice for most builders, Gypsum Exterior Sheathing has a place. There are a few variations of Gypsum Sheathing. Some Gypsum Sheathing has fiberglass or other outer coating options and a moisture-resistant core. 

Fire resistance is its main claim to the fam and most notable feature. With its enhanced outdoor durability, it’s also noise-dampening. Impact resistance and flexibility, on the other hand, are lacking. 

Installation Tips

  • Never counter-sink nails when installing wall sheathing.
  • Always flush nail exterior wall sheathing. 
  • Stagger joints when installing structural wall sheathing for increased wall strength.
  • Gap OSB and Plywood 3/16 to allow for expansion and contraction.
  • Crown each stud in the same direction if you are building a wall.
  • Use pressure-treated exterior wall sheathing on the lower sections and OSB on the upper to save cost.

Conclusion

Choosing the best exterior wall sheathing requires an additional budget and an assessment of needs and is often determined by the exterior cladding type. When installed correctly and with moisture prevention in mind, a quality exterior wall can be built using any of these materials. 

However, if you have an additional budget, plywood is generally more durable than OSB. Advanced systems combine insulation, sheathing, rain-shedding systems, and exterior siding, enabling efficiency, water resistance, and the rigidity your home needs.

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