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Lesson 4.2 Wall Sheathing

After completing the framework of a building, fasten a covering, known as sheathing, to it. Sheathing includes exterior wall sheathing, finish siding, and interior wall sheathing.

2-11. Exterior Wall Sheathing.

Sheathing is nailed directly onto the framework of the building. It is used to strengthen the building; provide a base wall to which finish siding can be nailed; act as insulation; and, in some cases, be a base for further insulation. Some common types of sheathing include wood, gypsum board, and plywood.

Wood Sheathing. Wood sheathing may be nailed on horizontally or diagonally (see Figure 2-21 ) however, diagonal application adds much greater strength to the structure. If the sheathing is to be put on horizontally, start at the foundation and work toward the top. If it is to be put on diagonally, start at the corner of the building and work toward the opposite wall.

Figure 2-21. Wood sheathing

 Gypsum Board. The long edges of the 4 by 8 boards are tongue-and-grooved. Gypsum board can be nailed (together with the wood siding) directly to the studs. Gypsum sheathing is fireproof, water resistant, and windproof. It does not warp or absorb water and does not require the use of building paper (see Figure 2-22 ).

Figure 2-22. Gypsum board sheathing

Plywood. Plywood is highly recommended for wall sheathing because of its weight, strength, and structural properties. Plywood is most commonly used because it adds a lot more strength to the frame than using diagonally applied wood boards. It comes in 4-feet-wide and 5- to 8-feet-long sheets, 1/4 to 3/4-inch thick. Install the sheets with the face grain parallel to the studs (see Figure 2-23 ). 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. Figure 2-24 shows how to fit plywood on rough or uneven walls.

Figure 2-23. Plywood sheathing


Figure 2-24. Fitting wall panels to uneven walls

2-12. Finish Siding.

Finish siding is the outside wood finish of the wall. Only board siding made of long, narrow boards will be covered in this section.

Vertical Wood Siding. Vertical wood siding is nailed securely to girts with 8d or 10d nails. The cracks are covered with wood strips called battens. To make this type of wall more weatherproof some type of tar paper or light-roll roofing may be applied between the siding and the sheathing. (See Figure 2-25 .)

Figure 2-25. Vertical wood siding

 Horizontal Wood Siding. Horizontal wood siding is cut to various patterns and sizes to be used as the finished outside surface of a structure (see Figure 2-26 ). It should be well-seasoned lumber. Siding is made in sizes ranging from 1/2 inch to 1 inch by 12 inches. Two types of siding are beveled and drop.

Figure 2-26. Horizontal wood siding

(1) Beveled Siding. Beveled siding is made with beveled boards, thin at the top edge and thick at the butt (see Figure 2-27 ). It is the most common form of wood siding It comes in 1 inch for narrow widths and 2 inches and over for wide types. It is nailed to solid sheathing, over which building paper has been attached.

Figure 2-27. Beveled siding

(2) Drop Siding. Drop siding is used as a combination of sheathing and siding or with separate sheathing. It comes in a wide variety of face finishes and is either shiplapped or tongue-and-grooved (see Figure 2-28 ). When sheathing is not used, the door and window casings are set after the siding is up. If sheathing is used and then building paper is added, drop siding is applied with beveled siding, after the window and door casings are in place.

Figure 2-28. Drop siding

2-13. 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 and 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 comer 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 (see Figure 2-29 ).

Figure 2-29. Cutting sheetrock

The keyhole saw is used for cutting 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 plum

Sawhorses are used for placing sheetrock on to make cut.

2-14. Interior Wail Coverings.

 Interior wall coverings are divided into two general types: wet wall material (such as plaster) and drywall material (including wood, sheetrock, plywood, and fiberboard). Only drywall will be covered in this subcourse.

Drywall. Sheetrock, fiberboard, and plywood usually comes in 4-foot-wide and 5- to 8-foot-long sheets, 1/4 to 3/4 inch thick. Drywall is applied in either single or double thicknesses with panels placed as shown in Figure 2-30 . When covering both walls and ceilings, always start with the ceilings. Use annular ringed nails when applying finished-joint drywall to reduce nail pops.

Figure 2-30. Drywall placement

 Drywall (Sheetrock) Installation. The three steps to installing sheetrock are hanging, finishing, and patching.

(1) Hanging Sheetrock. Apply sheetrock as follows:

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 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.

Determine the starting point of the wall. Using a measuring tape, locate a section where the studs are 8 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.

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 that proper nail spacing is maintained. Using a utility knife or sheetrock saw, cut out openings for doors and windows.

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 it. Measure and mark these dimensions for the receptacle cutout, allowing 1/16-inch clearance all around.

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.

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.

Lay out and cut sheets for corner posts. Measure and cut the required number and sizes of sheets to cover corner posts. Use scrap pieces of material if needed.

Install the corner bead. Using a corner-bead crimper, install the corner bead on the exterior corners of corner posts. Use nails if necessary.

(2) 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:

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.

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.

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 (see Figure 2-31 ). 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.

Figure 2-31. Covering joints

Use a 4-inch knife to apply a heavy coat of joint compound over the sheetrock at the inside corner (see Figure 2-32 ). 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.

Figure 2-32. Applying tape at corners

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.

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.

Apply the third coat of joint compound (see Figure 2-33 ). 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 inches on each side of the joint. Nails should not require a third coat, but it may be applied if necessary.

Figure 2-33. Finishing the joints

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.

(3) 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 by 2 or 1 by 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.

David L. Heiserman, Editor

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Revised: June 06, 2015