by Greg Winkler

Created on: January 10, 2009

Plywood is one of the most versatile and affordable products available for home projects. Use this guide to selecte the plywood, and other board products, most appropriate for your next project.

PLYWOOD

Plywood is an extremely strong product composed of thin sheets of veneers glued to each other at right angles. Plywood thickness varies, but the most common are ", ", and ". Panels with tongue and groove edges are available for use in sheathing floors. Minimum thicknesses for various applications: Roofing: "; Floor sheathing: "; Floor underlayment (installed atop the floor sheathing: "; Wall sheathing: ".

Types: Plywood comes in a dizzying variety of types, ranging from simple interior grade plywood, acceptable for normal inside woodworking projects to marine grade plywood, made with waterproof glues to resist moisture. Special plywood products made with smooth surfaces and no voids are called underlayments, and are appropriate for use on top of the plywood subfloor as a base for vinyl or ceramic tile and carpeting. If you're building furniture or cabinetry of any kind, you'll want to use hardwood veneer plywoods, made with a face veneer of oak, birch, maple, or walnut. Softwood veneers (pine or fir) are used for many siding, roofing, and general construction activities for their ease of nailing and general economy.

Grading: Plywood quality is determined by a grading system, with each face receiving its own letter grade: A is the highest quality (no major blemishes, sanded smooth); B grade may contain minor blemishes; C grade has noticeable patches and is not appropriate for finished products; D grade can contain holes, knots, and splits, and is used as a purely economy product where it will be hidden or appearances do not matter. In the case of hardwood veneers, a combination letter and number system is used, with the letter referring to the face grade and the number referring to the back grade (the opposite side of the board). These rankings range from AA for the best face grade to E for the lowest utility grade (pallets); and 1 for the best back grade to 4 for the worst.

Appearance: Plywood veneers are cut and arranged in different ways to achieve different looks. Most plywood is cut with a rotary blade, but flat-sliced veneers (produced by moving the log back and forth over a knife) result in the most attractive veneers. Here are the most common ways in which in which veneers are matched on a piece of plywood:

Random Matched: Veneers are not matched with any

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