Question
Can we avoid formaldehyde in adhesives by choosing hardwood flooring that is nailed into place?
Answer
The answer depends on your subfloor material and the product you’re installing.
If you have a plywood subfloor, solid hardwood flooring is typically fastened by nailing or stapling. (It’s less common nowadays to use screws.) A small number of flooring products are both nailed and glued to a plywood subfloor. It's best for indoor air quality to avoid using adhesive, but if you need to, you can use an option such as EcoTimber Healthy Bond, a resin-based product that has only 7 g/L of VOC. If possible, you can go the extra distance and choose a formaldehyde-free 3/4" plywood substrate.
If your subfloor is concrete, you may want to use a glueless engineered hardwood system instead of solid hardwood. These systems are fastened from the baseboards—a technique called "floating"—and no nails or adhesives are necessary.