There are six finish levels for drywall surfaces, used for walls, ceilings, or other drywall construction, that are defined by the major drywall construction, painting, and manufacturing trade associations. The levels are numbered from 0 to 5. These levels define, in detail, exactly what a certain level of finish means and must be so that there is no vagueness in the meaning of a finish. When you ask for a certain finish level, you get it.
From GA 214-96 and GA 214-90
This level has the designation of zero because there is no finish. There is no taping, no joint cement, and no painting. The drywall is erected and is then complete.
Recommended use: temporary construction, dust walls
There is taping at this level, but no painting. The taping at Level 1 is set in joint compound but does not have to be embedded in it. All drywall joints and interior angles are taped. Any excess compound is removed during application, and ridges and tool marks are OK. Levels 1 and 2 allow the presence of tool marks and ridges. Higher levels (3, 4, and 5) require that they be absent. Recommended use: areas not accessible to common traffic or the public, plenums above ceilings, attics, service corridors, and other concealed areas, hidden areas
As in Level 1, there is taping but no painting. However, the taping is more detailed and more extensive. At this level, again, all drywall joints and interior angles are taped, and at this level, the tape is embedded in the compound as opposed to merely being set and wiped with a joint knife to leave a thin coat of compound over the joints and angles. Also, all fastener heads (nails, screws, accessories) and beads are covered with one coat of compound. Like Level 1, excess compound is removed, and ridges and tool marks are OK here too. The definition of embedded in Level 2: Joint compound applied over the body of the tape at the time of tape embedment shall be considered a separate coat of joint compound and shall satisfy the conditions of this level.
Recommended use: garages, warehouses, and other storage areas
For a medium to heavy final paint texture or with heavyweight wall covering
The taping at Level 3 requires the tape to be embedded in compound (as in Level 2) with an additional coat of compound over the taped joints and angles. Any fastener heads and beads need two coats of compound, whereas in Level 2 you just needed one, and in Levels 0 and 1 you didn’t need any. At this level, the compound has to be smooth, and you can’t have any tool marks or ridges. In Levels 1 and 2, you could have them. In Level 3, you apply a coat of drywall primer after taping. Level 0 does not use joint compound, and so the presence or absence of tool marks on a Level 0 finish is not applicable.
Recommended use: With medium to heavy final paint texture or with heavy weight wall coverings. Level 3 isn’t used for smooth (flat or lightly textured) painted surfaces or with light to medium weight wall coverings
For flat paint, a light final paint texture, or with lightweight wall covering
In Level 3, you have an additional coat of compound over the embedded tape at the drywall joints and angles. Here in Level 4, you have two additional coats. The fastener heads, accessories, and beads are covered with three coats. The compound has to be smoothed, and there cannot be any tool marks or ridges and a coat of primer is applied after the taping.
Recommended use: with flat or light textured painted surfaces or with lightweight wall coverings. Enamel, semi-gloss, and gloss paint isn’t used with a Level 4 finish
For flat paint, enamel, semi-gloss, and gloss paint in severe lighting conditions
To get to Level 5, you take Level 4 before you apply the primer and add a thin skim coat over the entire surface. The skim coat is of joint compound or of a material manufactured specifically for this purpose. This skim coat is smooth and doesn’t have any tool marks or ridges. Then, the primer is applied.
Recommended use: for a flat paint surface with enamel, semi-gloss, other non-textured and gloss paints in severe lighting
In all of the levels that use drywall primer (3, 4, and 5), the term drywall primer means a high-quality, high-solids primer formulated to equalize the suction difference between gypsum board surface paper and the joint compound, and not just any sealer/primer of undetermined content.