The McIlvain lumber legacy certainly enhances our relatively recent dive into the unique branch of the lumber industry that is plywood. We made that leap in response to our customers’ frustration with the plywood market in general: the quest for quality plywood can be difficult. Sub-standard plywood is cheaply made, often resulting in cupping; by contrast, top-quality plywood maximizes the chief characteristic that makes plywood preferable to solid wood in the first place: stability. The secret to stable plywood is a combination of core construction, face veneer thickness, and proper manufacturing. If the core isn’t right for the application, then the rest doesn’t really matter.
Veneer Core Basics
The most often-used core is definitely veneer. Varying from 2 to 6.5 mm in thickness, the veneers are laid in alternating grain direction in order to create a stable substrate. As a result, typically more layers do produce a more stable product; however, the number of plies doesn’t always translate into greater stability or higher quality. The size and number of gaps between layers contributes to the grade of a sheet. Veneer-core plywood has the best crew-holding capacity of any core type. The species chosen definitely impacts the performance of the plywood, and each species has its own particular strength.
Common Veneer Species
One factor in determining the species is the manufacturer’s location. On the U.S. West coast, Fir core is quite common. Stable and resilient despite fluctuations in temperature and moisture levels, Fir veneer plywood has many excellent qualities. Its relatively soft layers provide an evening out of inconsistencies during compression; the screw-holding capacity for Fir veneer plywood is also quite remarkable.
Along the Eastern U.S., Poplar cores are more common; Poplar is heavier and harder than Fir yet still quite stable. At the same time, though, Poplar does lack the same weather-resistant properties as Fir, making it less than ideal for exterior applications. The hardness of Poplar means that knots and voids in the core end up affecting the surface veneer. With proper drying, Poplar veneer plywood can be a good choice for interior applications; however, if it is not dried correctly, Poplar core plywood can easily delaminate.
After Fir and Poplar, Aspen cores are commonly found, particularly in Western and Northern parts of the country. Similar to Fir but less dense, Aspen core plywood results in lighter-weight sheets. Like Fir, the softness leads to easy compression of fibers, resulting in a consistent face appearance.
Top-Quality Veneer Core
High-end plywood is typically comprised of Birch or Maple cores. Typically, plywood with these species consists of thinner, more plentiful plies than plywood that has Fir or Poplar cores. The thinner layers of these harder species create extremely stable products with no voids whatsoever. The high edge strength is both visually attractive and unlikely to splinter. For decorative applications for which exposed edges are important, using plywood with Birch or Maple cores is definitely best. Sometimes referred to as Apple Ply, Maple core plywood is the best stuff out there, and you can expect to pay top dollar for it as a result.