OSB Roof Installation

Oriented strand board, also known as OSB, is commonly used in the building trade.

Determining How Much OSB to Purchase

OSB is manufactured by gluing wood chips into sheets of varying thickness, but generally 4-by-8 feet in size. OSB is often used in roof construction as the sheeting over which roofing materials are applied (shingles, rolled roofing, metal, etc. ). There are some special techniques used when installing OSB as part of a roof construction project.

Calculate the square footage of the roof. OSB comes in 4-by-8 foot sheets, totaling 32 square feet each. Calculate the number of sheets needed for the roof project, allowing several extra for waste and cuts.

Determining the Thickness

OSB comes in various thicknesses. The thickness of the OSB used for a roofing project is determined by the spacing of the rafters. The OSB council recommends OSB sheeting between 5/16 inch and 7/16 inch for rafters that are placed 16 inches on center or less. OSB of 3/8 inch to 1/2 inch is recommended for rafters spaced 24 inches on center. OSB sheets 3/4 inch or thicker is suggested for rafters space up to 48 inches. Heavier OSB and longer nails should be used in areas prone to hurricanes or other high-wind weather patterns, regardless of the rafter spacing.

Applying OSB

When applied to a roof, the OSB sheets should be placed about one eighth of an inch apart to allow for expansion. According to the website of the Structural Board Association, the minimum spacing of the nails should be every 6 inches along the edges of the board and 12 inches on center in the middle portions of each OSB sheet. Standard 8 penny nails are used for fastening OSB to rafters in roofing applications. Longer nails should be used for heavier OSB is used.

Labels are printed on the OSB denoting the thickness and grade of the product. Many products also include a label denoting which side of the board should be placed facing up on the roof.

Finishing the Project

Moisture barrier and shingles should be applied to the roof as soon as possible. That prevents damage to the OSB from weather.

Installers of OSB should use caution during roof applications. OSB can be slippery when wet. Installers should use soft-rubber-soled shoes or boots and all proper safety equipment. Some brands of OSB apply texture to one side of the sheets to provide better traction.

About the Author

Keith Allen, a 1979 graduate of Valley City State College, has worked at a variety of jobs including computer operator, medical clinic manager, radio talk show host and potato sorter. For over five years he has worked as a newspaper reporter and historic researcher. His works have appeared in regional newspapers in North Dakota and in "North Dakota Horizons" and "Cowboys and Indians" magazines.