Level 0

This level is used in temporary construction and panels are unfinished, without taping, finishing or corner beads are required.

Level 1

Used in plenum areas above ceilings, garages, in attics, in
areas where the assembly would generally be concealed or in building
service corridors and other areas not normally open to public view.
All joints and interior angles shall have tape embedded in joint compound.
Tape and fastener heads need not be covered with joint compound. Tool marks and ridges are acceptable.

Level 2

Used with setting-type compound for areas where
water-resistant gypsum backing board is used as a substrate for tile.
All joints and interior angles shall have tape embedded in joint compound
and shall be immediately wiped with a joint knife or trowel, leaving
a thin coating of joint compound over all joints and interior angles.
Fastener heads and accessories shall be covered with a coat of joint
compound. Tool marks and ridges are acceptable.

Level 3

Used in areas which are to receive heavy texture
finishes before final painting, or where commercial-grade wallcoverings are to be applied as the final decoration. The prepared surface shall be coated with a drywall primer prior to the application of final finishes.

All joints and interior angles shall have tape embedded in joint compound and shall be immediately wiped with a joint knife or trowel, leaving a thin coating of joint compound over all joints and interior angles.

One additional coat of joint compound shall be applied over all joints
and interior angles. Fastener heads and accessories shall be covered
with two separate coats of joint compound. All joint compounds shall
be smooth and free of tool marks and ridges.

Level 4

Used where residential grade (light duty)
wall coverings, flat paints or light textures are to be applied. The prepared surface shall be coated with a drywall primer prior to the application of final finishes.   Joints and fasteners must be sufficiently concealed if the wallcovering material is lightweight, contains limited pattern, has a glossy finish or has any combination of these features. In critical lighting areas, flat paints applied over light textures tend to reduce joint photographing. Gloss, semigloss and enamel paints are not recommended over this level of finish.

All joints and interior angles shall have tape embedded in joint compound and shall be immediately wiped with a joint knife or trowel, leaving a thin coating of joint compound over all joints and interior angles.

In addition, two separate coats of joint compound shall be applied over
all flat joints and one separate coat of joint compound applied over
interior angles. Fastener heads and accessories shall be covered with
three separate coats of joint compound. All joint compounds shall be
smooth and free of tool marks and ridges. The prepared surface shall
be covered with a drywall primer prior to the application of the final
decoration.

Level 5

This level of finish is the highest level finish and is required where gloss, semigloss or enamel are specified or when flat joints are specified over an untextured surface, or where critical lighting conditions occur.
All joints and angles shall have tape embedded in joint compound
and immediately wiped with a joint knife or trowel, leaving a thin
coating of joint compound over all joints and interior angles. Two separate
coats of joint compound shall be applied over all flat joints and
one separate coat of joint compound applied over interior angles.
Fastener heads and accessories shall be covered with three separate
coats of joint compound. The prepared surface
shall be covered with a drywall primer prior to the application of the
final decoration.