While two coats of drywall mud are commonly used in many drywall finishing processes, it is not a hard and fast rule. The number of coats required for achieving a smooth and finished surface can vary depending on several factors, including the condition of the drywall, the desired level of finish, and the skill level of the person applying the mud.
In some cases, two coats of drywall mud may be sufficient to achieve a satisfactory result. However, there are situations where additional coats may be necessary. For example, if the drywall has significant imperfections or if a higher level of finish is desired, it may require three or more coats of mud.
It's important to note that each coat of drywall mud should be applied thinly and allowed to dry completely before applying the next coat. Additionally, proper sanding between coats is essential to achieve a smooth surface. This process helps to eliminate any imperfections and creates a uniform and even finish.
Ultimately, the number of coats required will depend on the specific circumstances of the project. It's best to consult with a professional or follow the recommendations provided by the manufacturer of the drywall mud for optimal results.