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Structural Plywood Vs Oriented Strand Board

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Many homeowners are not sure whether they should use structural plywood or oriented strand board (OSB) during a home renovation project such as placing that wood product as an underlayment for new floor tiles over existing tiles. This article gives a brief overview of the two materials. Use this information as you select which of these materials would be most suited to your home improvement project.

Structural Plywood

Structural plywood refers to plywood that is made without paying any attention to its appearance. Instead, emphasis is placed upon making it strong so that it can withstand the elements. Plywood is made by putting different layers of wood veneer (thin layers) perpendicular to each other. How are these veneers obtained? Compare a log to a pencil. The log is spun through a machine that peels off thin layers from around the log. These layers can be compared to what is removed as a pencil is sharpened. Those sheets are glued together using a cold-pressing machine. Plywood has many advantages. It is less likely to warp, shrink or swell. This is because the perpendicular arrangement of the veneers reduces the likelihood that the plywood will alter its shape in any given direction. Additionally, plywood quickly loses moisture once it gets wet. This makes it less likely to rot. On the downside, plywood can delaminate. De-lamination is the process by which a layer of a material peels off the surface. Plywood can have weak spots in places where holes in different layers of veneer overlap.

Oriented Strand Board

OSB is made by grinding wood chips into tiny strands. Those strands are mixed with an adhesive and wax. Next, the strands are formed into rolls of mats. The final stage is to use a hot-pressing machine to make panels out of the strand mats. The hot-pressing machine subjects the mats to intense heat so that the adhesive and wax bond the wood strands into a tough unified material. OSB has several advantages. It is more consistent because the grinding process creates a uniform paste from which evenly thick sheets are made. It is also free from de-lamination in the way plywood does. However, OSB easily breaks up when it absorbs moisture. This is because the adhesive degenerates quickly in the presence of water. It also loses moisture very slowly. This makes it more likely to rot.

As you can see, structural plywood and OSB each have their strengths and weaknesses. You should consult an experienced contractor like F.A. Mitchell & Company Pty Ltd for advice before you choose which of these two materials you should use for your project.