Drywall installation and finishing is ultimately about achieving a suitable surface. But that service ranges, depending on what project you're working on. Some finishes are strictly utilitarian, while others are high-end and decorative.
For example, many contractors finish the walls of attached garages only enough to achieve the fire rating mandated by building codes. While the surface is serviceable, it's often far from smooth. At the other end of the spectrum is a dining room wall that will have glossy paint and will be illuminated by ceiling canisters close to the wall that rake light across it at a shallow angle. Under those conditions, even a tiny imperfection will draw attention.
It's important that you finish your drywall with its end purpose in mind. Otherwise you waste time, energy, and money to achieve an unnecessarily smooth surface, or you risk disappointment with the final result by not investing enough into the project.
Understanding the various finish levels is especially important if you hire someone to install or finish drywall. Terms such as "industry standards" and "workmanlike finish" are vague and inadequate for contracts. That's why the Gypsum Association cooperated with several other trade organizations to draft a document that details the recommended levels of gypsum board finish. The following information summarizes that document, ASTM C 840-04, "Standard Specification for Application and Finishing of Gypsum Board." Contact the Gypsum Association for even more detailed information.
This level requires no taping, finishing, or corner beads.
You might specify this level of work from a contractor when you're going to do the finishing. Another example is an area where no decisions have yet been made on the ultimate finish.
All interior angles and joints should have tape set into joint compound. The surface should be free of excess joint compound. Ridges and tool marks are acceptable.
At this level, fasteners are not necessarily covered. In some municipalities, this level may be called "fire-taping" if it meets the code requirement for fire resistance. This level of finish is generally utilized for nonpublic areas of a building, such as a garage or attic.
At this level, all interior angles and joints should have tape embedded in joint compound and wiped with a trowel or joint knife, leaving a thin coating of compound. Fastener heads, corner beads, and other accessories are covered with a coat of joint compound. Ridges and tool marks are acceptable, but the surface should not have excess joint compound. If joint compound is applied over the tape when it is embedded, this is considered a separate coat of compound to satisfy the requirements of this level.
Level 2 is sometimes specified when water-resistant gypsum backerboard is used as a substrate for tile. This level is sometimes specified for garages and other areas where appearance is not important.
All joints and interior angles should have tape that's embedded in joint compound plus one additional coat of joint compound. Accessories and the heads of fasteners must be covered with two separate coats of joint compound. All joint compound must be smooth and free of ridges and tool marks.
For Level 3 and above, the prepared surface should be coated with a drywall primer that's compatible with the wallcovering, paint, or other decoration being applied to it. The application of primer, however, is usually outside the responsibility of the drywall installer and finisher.
All joints and interior angles should have tape that's embedded in joint compound plus two separate coats of compound over all flat joints and one separate coat over interior angles. Accessories and fastener heads are covered with three separate coats of joint compound. All joint compound is smooth and free of ridges and tool marks.
Specify this level when you'll apply a light texture, wallcovering, or flat paints. Gloss and semigloss paints are not recommended over this level. The weight and texture of wallcoverings must be carefully considered to ensure that joints and fasteners will be adequately concealed. Wallcoverings that are lightweight, glossy, or have limited patterns are especially vulnerable to revealing imperfections in the surface.
At level 5, all joints and interior angles have tape that's embedded in joint compound plus two separate coats of compound over all flat joints and one separate coat over interior angles. Accessories and fastener heads are covered with three separate coats of joint compound. A thin skim coat of joint compound is applied over the entire surface. The surface should be smooth and free of ridges and tool marks.
This level represents the highest quality of finish, and it is the one recommended where gloss, semigloss, or nontextured flat paints are used or where severe lighting conditions exist. It provides the most uniform surface and minimizes the possibility of joints or fasteners showing through the finish.