Interior Wall Coverings

After the rough framing is complete and a building is weather-tight, carpenters begin the inside
finish carpentry. However, finish carpentry may be optional for TO construction. This chapter
covers the following interior wall, partition, and ceiling coverings: gypsum board (or
sheetrock/wallboard), plywood, and fiberboard (or chipboard). It also covers interior wall and
ceiling moldings. (Doors and windows are covered in Chapter 8 and general information, such as
floor and wall tile, suspended ceilings, and painting, is covered in Appendix D.)

Over time, "sheetrock" has become the most common term for gypsum board. Also, the term "drywall
" is often loosely used to mean gypsum board /sheetrock / wallboard. In this manual we will use
,'sheetrock."

INTERIOR WALL AND PARTITION COVERINGS

In current construction, sheetrock, plywood, and fiberboard are used instead of laths and plaster to
cover walls. Sheetrock is normally applied in single (sometimes double) thickness as shown in
Figure 9-1, page 9-2.

NOTE: When covering walls and ceilings, always start with the ceiling. After the
ceiling is started, begin covering the wall in one corner and work around the
room. Make sure that joints break at the center line of a stud or ceiling joist.

PLYWOOD AND FIBERBOARD

Plywood and fiberboard can be used for interior wall coverings; however, plywood is most
commonly used. It comes in 4-feet-wide and 5-to 8-feet-long sheets, 1/4 to 3/4 inch thick. It is
usually applied vertically from the floor to the ceiling. When plywood is correctly applied (with
flush joints), the joints do not need to be concealed. However, to improve wall appearance, joints
may be covered with moldings. These may be battens fastened over the joints or applied as splines
between the panels. Less expensive plywood can be covered with paint or covered in the same way
as plastered surfaces. To hang plywood (or fiberboard), see Figure 9-1. Figure 9-2, page 9-3, shows
how to fit sheetrock on rough or uneven walls.

SHEETROCK

Sheetrock saves time in construction and has a short drying time as compared to plaster. It is also
fire-resistant. It requires moderately low moisture content of framing members. The dry. ing of
members will result in "nail pops," which cause the nailhead to form small humps on the surface.
Misaligning sheetrock on the studs may cause a wavy, uneven appearance. Wood sheathing will
correct misaligned studs on exterior walls.

Types of Sheetrock

The following are some of the different types of sheetrock used in construction:

· Gypsum board is the most commonly used wall and ceiling covering in construction today.
· Greenboard or blueboard is moisture resistant and is used in bathrooms, laundries, and similar areas.
· Sound-deadening board is a sublayer used with other layers of sheetrock (usually type X).
· Backing board has gray paper lining both sides. It is used as a base sheet on multilayer
applications and is not suitable for finishing and decorating.
· Foil-backed board serves as a vapor barrier on exterior walls.
· Vinyl-surfaced board is available in a variety of colors. It is attached with special sheetrock
finishing nails, screws, or channels and is left exposed with no joint treatment
· Plasterboard or gypsum lath is used for a plaster base. It is not compatible with Portland
cement plaster.

Sheetrock Dimensions

Sheetrock usually comes in
sheets that are 4 x 8, 4 x 9, 4
x l0, 4 x 14, and 4 x 16 feet.
Its thickness is 1/4, 3/8, 1/2, or
5/8 inch.

· 1/4 or 3/8 inch is used
effectively in renovations
to cover existing finish
walls with minor
irregularities. This
thickness is not adequate
for single-layer
application.

· 1/2 inch is most commonly
used. It is adequate for
studs or ceiling joists
spaced 16 or 24 inches on
center.

· 5/8 inch is widely used in
multiple, fire-resistant
combinations. It is
recommended for singlelayer
walls.

Sheetrock Edges

Sheetrock edges are tapered
1/16 inch thinner than the
body of the sheet about 1 1/4
inch on each sheet edge. The
shallow channel formed will
be brought level with tape and joint compound.

Sheetrock Application

Sheets may be applied either horizontally or vertically; specifications may indicate which method
should be used.

Sheetrock Fasteners

Nails used are specially designed with oversized heads for greater holding power and
treated to prevent rust and stains. The most common is the annular-ring nail. Other types
of nails include the smooth-shank, the diamond-head (used to attach two layers of
sheetrock or to attach sheetrock over existing materials), and the predecorated. The
predecorated nails have smaller heads, are left exposed, and are colored to match the
sheetrock.

Nails. If the sheetrock is single nailed, the nails should be spaced 6 to 7 inches apart on the
ceilings and 6 to 8 inches apart on the walls (Figure 9-3). If the sheetrock is double nailed, the
centers of the nail pairs are approxi mately 12 inches apart, with each pair 2 to 2 1/2 inches apart
and the outer edges 7 inches on center (Figure 9-4). The distance from the edge should be 3/8 to 1/2
inch. Do not double nail around the perimeter of a sheet.

Drive each nail slightly below the surface, forming a "dimple." Be sure not to break the paper when
driving nails. The dimple creates a pocket which is filled with joint compound. Screws are made of
high-quality steel; use a power screw gun or an electric drill to drive them in just below the surface
without breaking the paper.

Adhesives. Adhesives are
used to bond single-ply
sheetrock directly to the
framing members, furring
strips, masonry surfaces,
insulation board, or other
sheetrock. It must be used
with nails or screws.

Joint Compound. Joint
compound is used to apply
tape over joints, to cover
nailheads, and to smooth and
level the surface. The
powdered form is mixed with
water to a desired
consistency. It is also
available ready mixed. This
is the most common form and
the easiest to work with.

Joint Tape. Joint tape is applied with the first
coat of joint compound. It reinforces joints and
reduces cracking. The paper type may or may not
be perforated. Perforated tape is easier to bed and
cover than nonperforated tape. Fiber-mesh tape is
self-sticking, which eliminates the need for the
first coat of bedding joint compound.

Metal Accessories. Metal accessories include the
corner bead and the casing bead. The corner bead is
used on all exposed (outside) corners to ensure a clean
finish and to protect the outside corners of sheetrock
from edge damage It is nailed or screwed 6 inches on
center to en sure that it is plumb.

The casing (stop) bead is used where sheetrock sheets
butt at wall intersections or wall and exposed ceiling
intersections or where otherwise specified. It is
matched to the thickness of the sheetrock.

Sheetrock Tools

The following are tools used in the application of
sheetrock:

· The sheetrock hammer is used for hammering nails.
· The sheetrock carrier (lifter) is used for
carrying or lifting sheetrock.
· Sheetrock knives are used to apply and finish joint
compound. The 4-inch knife is used to bed the tape in the first layer of joint compound and for
filling the dimples, the 6-inch knife is used for feathering out the second coat, and the 12-inch
knife is used for the third/finish coat.
· The corner trowel flexes from 90° to 103°. It is used to apply joint compound in interior corners.
· The mud pan is used to hold and carry joint compound.
· The corner-bead crimper is used to fasten the corner bead by crimping.
· The T-square is used to lay out and guide a 90° cut on sheetrock.
· The utility knife is used to score or cut the sheetrock (Figure 9-5).
· The keyhole saw is used for cutting out irregular shapes and openings (such as outlet-box
openings).
· Surform is used to smooth sheetrock edges after cutting.
· The tape banjo is used to apply tape (dry) or joint compound and tape (wet).
· Sandpaper and sponges are used for feathering or smoothing dried joint compound.
· A chalk line is used to facilitate layout.
· A 16-foot measuring tape is used for measuring the sheetrock.
· A 4-foot hand level is used to plumb.
· Saw horses are used for placing sheetrock on to make cuts.

Sheetrock Installation

There are three steps to installing sheetrock— hanging, finishing, and patching.

Hanging Sheetrock

Apply sheetrock as follows:

Step 1. Install sheetrock on the ceiling first. Measure the distance from the inside edge of the top
plate to the outside edge of the second ceiling joist. Measure and cut a piece 48 inches long and to
the width measured above. Install and secure the sheet to the ceiling with
sheetrock nails. Nail spacing on ceilings is 5 to 7 inches on center.

Step 2. Determine the starting point of the wall. Using a measuring tape, locate a section where
the studs are ~ foot on center and where a full sheet could be laid horizontally. Check the layout to
ensure that there will be no joints above or below the door or window openings. Sheets will be
installed from the ceiling down to the floor, starting at the ceiling.

Step 3. Install the first sheet. With the help of another person, place a sheet of sheetrock
in position so that the edges fall on the center of the studs. Place the sheet snug against
the ceiling, using a hand level to ensure that it is level. Secure the sheet with sheetrock
nails 6 to 8 inches on center, 3/8 inch from the edge. Install succeeding sheets on the top
half of the wall against installed sheets, ensuring that joints fall on the center of the studs and
proper nail spacing is maintained. Using a utility knife or sheetrock saw, cut out openings for
doors and windows.

Step 4. Lay out the receptacles. Measure the distances from an inside corner to both sides of the
receptacle box and record them. Measure the distance from the installed sheetrock to the top and
bottom of the receptacle box, and record them. Measure and mark these dimensions for the
receptacle cutout, allowing 1/16-inch clearance all around.

Step 5. Cut out the opening for the receptacle. With a utility knife, drive a hole within the opening.
Using a keyhole saw, cut out the opening. Use a slight undercut bevel so that the back opening is
larger than the front opening.

Step 6. Install the prepared sheet. Place the prepared sheet in position, ensuring that the
receptacle fits in the opening without breaking the paper. Make adjustments to the opening if
necessary. Secure the sheet to the studs with sheetrock nails. Using a Surform, smooth the rough
edges of the openings as necessary.

Step 7. Lay out and cut sheets for corner posts. Measure and cut the required number and sizes of
sheets to cover corner posts. Scrap pieces of material may be used.

Step 8. Install the corner bead. Using a corner-bead crimper, install the corner bead on the exterior
corners of corner posts. Nails may be used if necessary.

Finishing Sheetrock

The finishing process consists of covering nailheads and covering seams
(covering seams is also referred to as finishing joints). Finish sheetrock as follows:

Step 1. Check for improperly recessed nails by running the edge of a sheetrock knife over the
nailheads. A clicking sound indicates a nail needing to be recessed.

Step 2. Use a 4-inch knife and mud pan with joint compound to apply a smooth coat of joint
compound over the nails. Remove any excess compound.

Step 3. Use the knife and mud pan to apply a heavy coat of joint compound over a sheetrock joint,
horizontal or vertical. A heavy coat is enough to ensure a good bond between the tape and
sheetrock and to fill in tapered edges. Measure and cut the tape to the length required for a joint.

Keeping the tape centered over the joint, start at one end of the joint and work toward the opposite
end. Using the knife, press the tape into the compound, removing all excess compound. Work off all
excess joint compound, being careful not to wrinkle the tape or leave air bubbles. Continue to tape
all the joints in the same manner.

Step 4. Use a 4-inch knife to apply a heavy coat of joint compound over the sheetrock at the inside
corner. Measure and cut the tape to the length required for the joint. Fold the tape in half
lengthwise, keeping both edges even. Use a corner tape creaser if necessary. Apply the tape at the
top and work downward, running the edge of your hand at the center of the tape to ensure that it
is in the corner. Using the inside corner tool, press the tape into the compound, working off all
excess compound and being careful not to wrinkle the tape or leave air bubbles.

Step 5. Apply the first coat of joint compound over the tape then apply a medium coat of joint
compound. Feather the compound with the 6-inch knife to about 2 to 3 inches on each side of the
joint. A good job of feathering and smoothing will minimize sanding later.

Step 6. Apply the second coat of joint compound over the tape and nail coverings. The joint
compound previously applied must be completely dry. Use the 4-inch knife to apply a thin
coat of compound over the nails, removing any excess compound. Using the steps above, apply
the second coating to the joints using the 6-inch knife and feathering out 6 to 8 inches on each side
of the joint.

Step 7. Apply the third coat of joint compound. The joint compound previously applied must be
completely dry. Using the step above, apply the third coat using the 10-inch knife and feathering
out 10 to 12 on each side of the joint. Nails should not require a third coat, but it may be applied if
necessary.

Step 8. Using a damp sponge or fine sandpaper, sand the surface to a smooth finish, ensuring that
there are no voids and that the surface is ready to receive paint.

Patching Sheetrock

There are several different methods of patching sheetrock, depending on
the size of the hole.

For small holes, apply fiber-mesh tape directly over the hole. Cut the tape with joint compound
and feather the edges. Sand or sponge the area smooth after it has dried.

For fist-size holes, cut out a rectangle around the hole with a keyhole saw. Cut a piece of backing
(1 x 2 or 1 x 3) slightly larger than the opening itself. Glue or screw the backing into place. Cut a
patch and glue it to the backing using either wallboard adhesive or mastic. Apply tape and coat it
with compound. Feather the edges. Sand or sponge the area smooth after it has dried.

For large holes, mark and cut a rectangular section around the damaged area, reaching from the
centers of the nearest studs. Cut a patch and screw or nail it to the studs. Apply tape and coat it
with compound. Feather the edges. Sand or sponge the area smooth after it has dried.