Panel Cores

Plywood is composed of at least three elements: a face, a back and a core. Holding these pieces together is the glue line or glue. Each type of core has a specific use and represents a better value or better product for the specific use. The most common type of core used prior to World War II was veneer core.

• Veneer Core: Layers of veneer are pressed together in alternating perpendicular layers balanced on either side of a central core layer. This type of plywood is more prone to surface irregularities and defects, but it exhibits greater strength in bending and in stress than the other core types.

• Particle Core or Chip Core: Particle core is produced in large plants on a continuous press line from wood chips, glue and resins and then cut up into panels. Its surface is smooth, but some small voids are always present.

• Fiberboard: Fiberboard is the flattest and smoothest core for plywood. Medium density fiberboard (MDF) makes a superb carrier for veneer. It has few surface imperfections or voids and is dimensionally stable and flat.

Lumber Core: Lumber Core is manufactured from thin strips of lumber glued on edge and covered by a veneer crossband perpendicular to the core’s grain direction. When lighter cores are required or specific strength in one direction is required, lumber core plywood is often used.

• Fire-Retardant Cores: Fire-Retardant Cores are usually made of particle core with fire resistant salts added to the chips and glue when pressed. In many cases, fire rated codes are required for paneling in entries, lobbbies, and areas of public spaces. This type of core is weaker and more prone to expansion and contraction than standard particle core or medium density fiberboard. Fire rated veneer core is usually less flat and prone to warping. Fire rated medium density fiberboard is not as available as fire rated particle core.

• Engineered Wood Cores: Engineered wood is a new type of core utilizing the strength and lightness of veneer core, but having improved flatness, rigidity and dimensional stability. The core is made of linear strips of thick fibrous veneer glued and pressed together in an irregular pattern.

• Water Resistant Cores: Water Resistant Particle Core, Water Resistant Veneer Core and Waterproof Veneer Cores are available. The Architectural Woodwork Institute Quality Standards require that all Premium Grade tops maed for use in wet areas, such as near a sink, be made from water resistant or waterproof cores.