COREtec Flooring Features. 1  Patent-pending* COREtec Plus construction with WATERPROOF extruded core board. 2  WILL NOT SWELL when exposed to water. 3  WILL NOT EXPAND OR CONTRACT.  No need for transition strips in large 1  rooms. Easy to install Drop & Lock glueless profile.  NO UNDERLAYMENT 1  REQUIRED. Can be installed over other hard surface flooring.