Beyond Wood Engineered flooring is a sandwich of layers, called “plies,” of hardwood and plywood bonded together via a heating and pressing process.
The top layer, the one you see, is a veneer of hardwood 1/16" to 3/8" thick. Beneath that veneer is a core of plywood, with each ply lying perpendicular to the other to give the flooring strength and stability, and make it less susceptible to expansion and contraction.
Engineered flooring can have as few as three plies or as many as 12—the more layers, the better the quality of the floor.
Because of the veneer, it’s visually difficult to tell the difference between a solid wood floor and an engineered one once they have been laid. The plies are visible from the side before engineered flooring is installed, however.
Beyond Wood Engineered flooring holds up in spaces that get light moisture, such as bathrooms, kitchens, basements, and over concrete floors, but it isn’t going to last in a high-moisture situation—a basement that tends to flood, for instance.
When using engineered flooring, the moisture content in an adjacent concrete slab cannot exceed 4 percent (the space must be tested first to pinpoint exact levels of moisture), and a vapor barrier underlayer is recommended in moisture-prone areas.