Titebond 821 Premium Urethane Wood Flooring Adhesive is a high-performance formula ideal for bonding engineered, solid plank, cork underlayment and bamboo flooring to common underlayments and subfloors. Its non-slumping characteristics, not available in other urethane adhesives, allow the troweled ridges to bridge normal gaps between the wood flooring and the subfloor, virtually eliminating hollow and popping spots. It also offers excellent green grab and develops a superior bond that will remain flexible for the lifetime of the floor. Titebond 821 Premium is a moisture-resistant adhesive that allows the installer to wet lay the wood flooring without the traditional risks of solvent- and water-based adhesives. In addition, it is mold and mildew resistant. Titebond 821 Premium delivers exceptional performance characteristics that exceed the expectations of professional installers.