The three main terms used to describe the required strength of an existing or newly installed substrate are “structurally sound,” “solid” and “stable.” “Structurally sound” is a common construction term that indicates that a material is strong, sturdy and well made. “Solid” is a general term that describes a material as being dense and free from damage and defects. “Stable” refers to the material as being firmly supported, securely fastened and inflexible.
