Plywood is widely used in home construction because it is cheaper than solid wood, and in some ways stronger. A manufactured product, plywood is made of several layers, or plys, of wood glued into a sandwich. Construction-grade plywood is generally made from softwood trees while furniture-grade plywood is usually made from hardwood trees. Plywood is sold primarily in 4' x 8' sheets.

Virtually all construction-grade plywood, both interior and exterior grade, is made with phenol-formaldehyde (PF) glue. In the past, interior-grade construction plywood was made with urea-formaldehyde (UF) glue. Products containing UF glue outgas significantly more formaldehyde than those produced with PF glue. Interior-grade construction plywood that is stamped by the American Plywood Association (APA) indicates PF glue was used in its production.

While construction-grade plywood is less noxious than it once was, UF glue is still used in interior, furniture-grade plywood. Furniture-grade plywood can cause and/or trigger health problems and should be avoided.

Exterior vs. Interior Use

When used for a roof deck or for sheathing under siding, the lower outgassing construction-grade plywood will be separated from the living space and it generally won’t bother a sensitive person—especially if a house is very tightly constructed.

When plywood is used for a subfloor, it is much closer to the occupants and could bother someone sensitive to formaldehyde. An aluminum-foil diffusion retarder placed between a plywood subfloor and a hardwood finish floor will tend to block the formaldehyde from diffusing into the living space.

Furniture-grade plywood generally has a hardwood surface veneer and is widely used in furniture, cabinetry, and wall paneling. The UF glue in these wood products can outgas significant amounts of formaldehyde from months to years after installation. 

Low-Emission Interior Products

Realistically, the only way to obtain low-emission furniture-grade plywood product is to have it custom made. While feasible, this can add cost to a project—sometimes substantially.

Some manufacturers will custom make small quantities (even 1-2 sheets) of a veneered product to your specifications. The production process involves using a low-emission base material and laminating any number of different veneers (such as oak, cherry, hickory, or even exotic imported woods) to the front and back surfaces with a variety of different glues (such as a PF glue or a polyvinyl-acetate glue).

Hybrid plywood/fiberboard products are also available that have lower formaldehyde emissions than some other furniture-grade products.

Excerpted from:
The Healthy House, 4th Edition
John Bower, Author
Copyright © The Healthy House Institute