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Sheetrock is a building material used to cover interior walls and ceilings. It’s also a brand name for drywall. Although drywall is generally used indoors, it can be installed in outdoor applications in some circumstances.
Sheetrock can be used outside as long as it is protected from moisture. It is highly absorbent, meaning that it tends to wick water from the ground. If it is not protected from moisture or exposed to high levels of moisture, sheetrock will begin to deteriorate rather quickly.
For sheetrock to be used outdoors, it must have a waterproof cover. An outdoor roof overhang can provide this protection if applied correctly, and in some cases, an existing roof can serve as a protective barrier. In this article, I’ll explain a few circumstances when using sheetrock outside is acceptable and what other materials can be used in place of sheetrock.
When Using Sheetrock Outside Is Acceptable
Sheetrock is made of gypsum sandwiched between layers of paper. The target area on an individual sheet is 4 feet by 8 feet (1.21 by 2.43 meters) and 2-1/2 inches (5.08-1.27 cm) thick. Drywall sheets are usually hung with a standard metal hanging system which can also contain electrical wiring and insulation.
These sheets come in various grades, including fire-resistant types typically used around boilers, furnaces, or in high-humidity areas such as bathrooms or closets. Using sheetrock outside is acceptable when it will be covered by brick, stone, or siding.
Using sheetrock outside is acceptable if proper precautions are taken, including care in selecting the grade and installing it correctly. Additionally, it can only be used outdoors if there’s an adequate layer of waterproofing material between the sheeting and earth or other combustible surfaces that could come into contact with the back of the sheet.
Alternatives To Using Sheetrock
If you’re considering using Sheetrock on an exterior wall, you should know that there are several different types of products made specifically for outdoor applications that may work better with your design plans. These include:
Structural Fiberboard Exterior Sheathing
Structural fiberboard is specifically designed for exterior applications. It’s made of tough cellulose fibers, which are compressed under high pressure with wax, resins, and other binders to create a product that is stronger than plywood. It resists moisture penetration, termites, mold, and mildew growth.
It is appropriate not only for new construction but also for renovations or repairs where existing walls need replacing or additional support in a structural manner. For renovation projects in which you will reuse the studs in the wall, you can attach the structural sheathing over them directly without adding additional furring strips.
Plywood sheathing is often used as replacement sheathing for old or damaged walls. Like structural fiberboard, it provides strength and protection against water damage.
Despite its name, plywood sheathing is made without wood fibers but instead from veneer sheets of softwood that are laminated together with resins to create a sturdy surface. It can be nailed directly to studs or onto furring strips. Plywood usually comes in 4-foot by 8-foot (1.21 by 2.43 meter) sheets that are ½ inch (1.27 cm) thick, though other thicknesses are also available.
Foam Board Wall Sheathing
Foam board wall sheathing is an insulated form of exterior wall sheathing that’s often used in commercial construction.
Foam board is made with expanded polystyrene (EPS) or extruded polystyrene (XPS), which are lightweight plastic foams that provide excellent insulation. The sheets are faced on one side with a water-resistant material, usually oriented strand board (OSB).
One of its most popular applications is foam board siding, where it can replace wooden clapboards and be painted to match the exterior color of the building. However, there are numerous other options for using foam board as sheathing, including replacing plywood sheathing on old structures or providing additional structural support for new walls.
Can Sheetrock Ever Be Used Outside?
Sheetrock can be used outside but only if certain conditions are met for it to remain water-resistant. Since water naturally conducts electricity, any hole or gap in foam board insulation will let electricity flow through and possibly damage electrical fixtures and appliances inside the building.
Before using sheetrock as an exterior sheathing material, a contractor should review the building plans with a structural engineer to ensure that the specific wall assemblies meet all of the strength and seismic requirements necessary for codes in your area.
How To Protect Exterior Sheetrock
Once the drywall has been approved for outdoor use, there are several steps you can take to protect it from the elements. The simplest means of weatherproofing is to install house wrap behind the exterior siding. This ensures that no rainwater or moisture can seep between them.
House wrap is typically made of water-resistant layers of spun plastic, which are both waterproof and vapor pervious. This allows the moisture from rain or snow to pass through but keeps it from seeping into the interior of your home.
House wrap is typically available in rolls with a slit down the middle. You’ll apply this similar to how you would apply window flashing — starting at the bottom edge and working up to the top.
What Happens if You Don’t Protect Exterior Sheetrock
One of the most common mistakes homeowners make is applying sheetrock on a deck or porch without protecting it in some way. Moisture can quickly damage the sheetrock and cause mold to grow behind it, which would lead to rotting.
If you fail to protect exterior sheetrock, some problems you’ll face include:
- Mold growing behind the sheetrock, causing unsightly discoloration and creating a health hazard by emitting spores.
- Moisture seeping through the unprotected surface, causing rotting of wood beams.
- Drywall edges curling up over time due to exposure to extreme moisture levels. This can be especially harmful because it allows water into your home’s interior walls.
Since sheetrock is manufactured to resist water, it’s resistant to moisture when used inside a home. However, because the exterior sheetrock doesn’t have any kind of water-resistant material on the backside, rain and snow can easily seep through. This allows moisture to get behind the sheetrock and into your home, where it can cause problems such as mold growth and rot.
Sheetrock is very versatile and used in many different parts of homes, including ceilings, walls, and even floors. You’ll find sheetrock installed directly on top of framing members inside homes, including studs and joists.
Using sheetrock on the exterior of your home is possible, but it can easily be compromised by water penetration. If you’re looking to use sheetrock on the exterior of your home, it’s best that you have a moisture barrier installed behind the sheetrock.
- Innovative Building Materials: Exterior Wall Sheathing Options
- Home Depot: House Wrap
- Green Clean Care: What Happens When Drywall Gets Wet?
- This Old House: All About Walls
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Giovanni Valle is an architect, designer, internet entrepreneur, and the managing editor of various digital publications including BuilderSpace, Your Own Architect, and Interiors Place. He is the founder of BuilderSpace LLC.