Sanding as Part of a Drywalling Project

• Sanding of a drywall project almost invariably means sanding the taped and coated joins between panels. This is necessary to create a flaw-free appearance under even the most unforgiving of finishes, such as paint. The joint tape is covered by an extremely thin layer of joining compound, and it is this that must be sanded after it has dried.
  
  

Types of Drywall Compound

• Two types of premixed drywall compound -- universally referred to as “mud” by installers -- are commonly available. Only sandable compound is intended for joining; non-sandable product is intended for use in building up, such as on an outside corner, and is as hard as concrete when cured. Ensure the correct product is chosen for the application.
  
  

Technique

• Sanding the join flat is not the objective. Drywall joins are not intended to be sanded back until the full face of the panel is once again visible up to its edge, leaving only a bead of fill between one panel and the next. Rather, the object is to smooth away the coating so that it blends seamlessly into the surfaces of the drywall panels on either side. This is properly called “feathering,” or creating a “transition edge.” A competent installer will have left the project feathered, such that very little subsequent dry sanding is necessary; certainly, it should not be obligatory to sand to such a degree that the texture of the tape becomes evident or the surface of the drywall panels is distressed. Following a competent installer, therefore, any type of drywall can be sanded.
  
  

The Best Drywall for Sanding

• Many professionals use water-resistant drywall, even where such an application is not expected to be necessary, because the color contrast makes sanding easier. While most types of drywall have a pale finish that is similar to the dried compound, water-resistant drywall is green.
  
  

Methodology

• Sanding by hand using a sanding sponge is by far the best system for amateurs; it minimizes any risk of damage to adjacent drywall surfaces. Special drywall sanders are available to rent at many home improvement warehouses. They attach to the hose of a regular shop-vac and leave a smooth finish while minimizing area contamination. Attachments are available that work right into corners and along cornice and baseboard lines.