Sheathing in home construction, refers to the boards applied to the outside studs, joists and rafters of a house, to strengthen the structure and provide a wind barrier. While the term is most commonly used to refer to the outside skin of a house, it sometimes also refers to any surface on which other materials can be applied … which can include floors.
According to HealthyHouseInstitute.com, “Sheathing was not used when 2×4 construction was first developed in the early 1800s. As a result, many old buildings have leaned out of square because of a lack of bracing. Without sheathing, houses were less resistant to the wind—it simply blew right through the cracks into the living space.”
The concept of sheathing is easy to understand. When your builder or contractor recommends a product other than plywood or OSB, it's worth your time to ask questions and understand the pros and cons.
Where is Sheathing Found
- Exterior walls of a house.
- Roof of a house, which is also called the roof deck.
Some people may call sub-flooring (fastened to the floor) a form of sheathing. It is structural and often made from plywood or OSB, . In fact OSB comes in 3 grades – sturdy floor, rated siding and rated sheathing.
Materials Used for Sheathing
- Wood – isn't used any longer due to cost. You may find diagonal wood boards at the corners of a house for structural bracing, used in combination with non-structural sheathing.
- Plywood – has been used as sheathing for many years, and more recently, it's being replaced by OSB which uses less wood.
- Oriented Strand Board (OSB) – which provides similar rigidity when nailed properly.
- Fiberboard – is made of various plant fibers held together with an asphalt binder. It provides more insulation value than plywood or OSB, is lower in cost … but doesn't provide enough wind bracing and rigidity by itself.
- Foam sheathing – was used in the 19702 during the energy crunch, but adds no strength to a wall so it's corners require diagonal boards or wood/metal strapping in notches, to provide required rigidity.
- Insulated sheathing – doesn't provide structural rigidity. It offers various R-values using a number of different materials including plastic, foam, cellulose fiber, paper faced and foil faced boards.
- Other sheathing products – include gypsum, fiber cement sheathing and cement board. They vary in their ability to withstand moisture and those which are combustible require coatings to meet building codes.