Walls and Partitions

WALLS AND PARTITIONS

Once the floor is in place, it is used to support the wall frame. Wall framing (Figure 6-28) consists of studs, diagonal bracing, cripples, trimmers; headers, and fire blocks. It is supported by the floor sole plate. The vertical members of the wall framing are the studs. They support the top plates and the upper part of the building, or everything above the top plate line. Studs support the lath, plaster, and insulation on the inside and wall sheathing on the outside.

Walls and partitions, which are classed as framed constructions, are composed of studs. Studs are usually closely spaced, slender, 2 x 4 vertical members. They are arranged in a row with their ends bearing on a long horizontal member called a bottom plate or sole plate, and their tops are capped with another plate, called a top plate. Double top plates are used to tie walls and partitions together. The bearing strength of stud walls is determined by the strength of the studs. Figure 6-29, page 6-24, shows a typical wall construction.

Partition walls divide the inside space of a building. In most cases, these walls are framed as part of the building. Where floors are to be installed, the partition walls are left unframed.

The two types of partition walls are bearing and nonbearing. The bearing type supports ceiling joists; the nonbearing type supports only itself, and may be put in at any time after the other framework is installed. Only one cap or plate is used. A sole plate should be used in every case, as it helps distribute the load over a larger area.

Partition walls are framed the same as outside walls; door openings are framed as outside openings. Where there are corners or where one partition wall joins another, corner posts or Tposts are used as in the outside walls. These posts provide nailing surfaces for the inside wall finish. Partition walls in a TO one-story building may or may not extend to the roof. The top of the studs has a plate when the wall does not extend to the roof. If the wall extends to the roof, the studs are joined to the rafters.

CORNER POSTS

A corner post forms an inside corner and an outside corner which provides a good nailing base for inside wall coverings. Figures 6-30, page 6-24, and 6-31, page 6-25, show two of the most common types of corner posts as they would appear constructed. The studs used at the corners of frame construction are usually built up from three or more ordinary studs to provide greater strength. These built-up assemblies are called corner posts. They are set up, plumbed, and temporarily braced. Corner posts may also be made in any of the following ways (Figure 6-32):

· A 4x 6 with a 2 x 4 nailed on the board side, flush with one edge (Figure 6-32, A). This type of corner is for a 4-inch wall. Where walls are thicker, heavier timber is used.
· A 4 x 4 with a 2 x 4 nailed to each of two adjoining sides (Figure 6-32, B).
· Two 2 x 4s nailed together with blocks between them and a 2 x 4 flush with one edge (Figure 6-32, C). This is the most common method.
· A 2 x 4 nailed to the edge of another 2 x 4, the edge of one flush with the side of the other

(Figure 6-32, D). This type is used extensively in the TO where no inside finish is needed.

PARTITION POSTS

There are two types of partition
posts—T-posts and double Tposts.

T-Posts

Whenever a partition meets
another wall, a stud wide
enough to extend beyond the
partition on both sides is used.
This provides a solid nailing
base for the inside wall finish.
This type of stud is called a T-
post and is made in any of the following ways (Figure
6-33):

· A 2 x 4 may be nailed and centered on the face side
of a 4 x 6 (Figure 6-33, A).
· A 2 x 4 may be nailed and centered on two 4 x 4s
nailed together (Figure 6-33, B).
· Two 2 x 4s may be nailed together with a block
between them and a 2 x 4 centered on the wide side
(Figure 6-33, C).
· A 2 x 4 may be nailed and centered on the face side
of a 2 x 6, with a horizontal bridging nailed behind
them to give support and stiffness (Figure 6-33, D).

Double T-Posts

When a partition is finished on one side only, the
partition post used is a simple stud, set in the outside
wall, in line with the side of the
partition wall, and finished as shown
in Figure 6-34, page 6-26. These posts
are nailed in place along with the
corner posts. The exact position of the
partition walls must be determined
before the posts are placed. When
walls are more than 4 inches thick,
wider timber is used.

In special cases (for example, where
partition walls cross), a double T-post
is used. It is made as described above,
and by nailing another 2 x 4 to the
opposite wide side, as shown in Figure
6-34, A, B, and C (C is the most
common).

STUDS

After the sills, plates, and braces are
in place and the window and door
openings are laid out, the studs are
placed and nailed with two 16d or 20d
nails through the plates. The
remaining studs are laid out on the
sills or soles by measuring, from one
corner, the distances the studs are to
be set apart. Studs are normally
spaced 12, 16, or 24 inches on center,
depending upon the outside and
inside finish material. If vertical
siding is used, studs are set wider apart since the horizontal girts between them provide a
nailing surface.

To double the post of the door opening, the outside studs are first placed into position and
nailed securely. Then short studs (or trimmers) the size of the vertical opening are cut and nailed to the inside face of the outside studs as shown in Figure 6-35 on the sole plate. The sill of a window opening must be framed. This sill is specified single or double. When it is double, the top header is nailed to the opening studs at the correct height and the trimmer next. The sill headers are toenailed to the trimmer. The door header is framed as shown in Figure 6-35. The jack stud rests on the sole plate.

GIRTS

Girts are always the same width as the studs and are flush with the face of the stud, both outside and inside. They are used in hasty construction when the outside walls are covered with vertical siding. Studs are placed from 2 to 10 feet apart, with girts spaced about 4 feet apart, running horizontally between them. The vertical siding acts in the same way as the studs and helps carry the weight of the roof. This type of construction is used extensively in the TO.

TOP PLATE AND SOLE PLATE

The top plate ties the studding together at the top and forms a finish for the walls. It supports the lower ends of the roof rafters. The top plates serve as connecting links between the wall and the roof, just as the sills and girders are connecting links between the floors and the walls. The plate is made up of one or two pieces of framing lumber the same size as the studs.

If the studs at the end of the building extend to the rafters, no plate is used at the end of the building. When used on top of partition walls, the plate is sometimes called the cap. Where the plate is doubled, the first plate or bottom section is nailed with 16d or 20d nails to the top of the corner posts and to the studs. The connection at the corner is made as shown in Figure 6- 36. After the single plate is nailed securely and the corner braces are nailed into place, the top part of the plate is nailed to the bottom section with 10d nails. The plate may be nailed over each stud or spaced with two nails every 2 feet. Care must be taken to make sure all joints are staggered. The edges of the top section and the corner joints are lapped.

All partition walls and outside walls are finished either with a 2 x 4 or with a piece of lumber the same thickness as the wall. This lumber is laid horizontally on the floor or joists. It carries the bottom end of the studs, and is called the sole or sole plate. The sole should be nailed with two 16d or 20d nails at each joist it crosses. If it is laid lengthwise on top of a girder or joist, it should be nailed with two nails every 2 feet.

BRIDGING

Frame walls are bridged, in most cases, to make them more sturdy. There are two methods of bridging—horizontal or diagonal (Figure 6-37).

Horizontal

Horizontal bridging is nailed
between the studs horizontally
and halfway between the sole and
top plates. This bridging is cut to
lengths that correspond to the
distance between the studs at the
bottom. Such bridging not only
stiffens the wall but also helps
straighten studs.

Diagonal

Diagonal bridging is nailed
between the studs at an angle. It
is more effective than the
horizontal type since it forms a
continuous truss and keeps the
walls from sagging. Whenever
possible, interior partitions and
exterior walls should be bridged
alike.

PLUMBED POSTS AND
STRAIGHTENED WALLS

After the corner post, T-post, and
intermediate wall studs have been
nailed to the plates or girts, the
walls must be plumbed and
straightened so that permanent
braces and rafters may be
installed. This is done by using a
level or plumb bob and a chalk
line.

Plumbing Posts

There are two methods for plumbing posts.

Method 1. To plumb a corner with a plumb bob—

Step 1. Attach a string to the bob. The string should be long enough to extend to or below the bottom of the post.

Step 2. Lay a rule on top of the post so that 2 inches of the rule extend over the post on the side to be plumbed.

Step 3. Hang the bob line over the rule so that the line is 2 inches from the post and extends to the bottom of it, as shown in Figure 6-38.

Step 4. With another rule, measure the distance from the post to the center of the line at the bottom of the post. If it does not measure 2 inches, the post is not plumb.

Step 5. Move the post inward or outward until the distance from the post to the center of the line is exactly 2 inches, then nail the temporary brace in place.

Step 6. Repeat this procedure from the other outside face of the post. The post is then plumb.

NOTE: This process is carried
out for each corner post of the
building. If a plumb bob or
level is not available, use a
rock, half-brick, or small piece
of metal.

Method 2. An alternative method
of plumbing a post is shown in the
inset in Figure 6-38. 1b use this
method—

Step 1. Attach the plumb-bob
string securely to the top of the
post to be plumbed. Be sure that the
string is long enough to allow
the plumb bob to hang near the
bottom of the post.

Step 2. Use two blocks of wood,
identical in thickness, as gauge
blocks.

Step 3. Tack one block near the top of the post between the plumb-bob string and the post (gauge block 1).

Step 4. Insert the second block between the plumb-bob
string and the bottom of the post (gauge block 2).

Step 5. If the entire face of the second block makes contact
with the string, the post is plumb.

Straightening Walls

The following procedure is carried out for the entire
perimeter of the building. Inside partition walls should be
straightened the same way (Figure 6-39).

Step 1. Plumb one corner post with a level or a plumb bob.
Nail temporary braces to hold the post in place. Repeat
this procedure for all corner posts.

Step 2. Fasten a chalk line to the outside of one corner post
at the top and stretch the line to the corner post at the
opposite end of the building. Then fasten the line to this
post.

Step 3. Place a 3/4-inch block under each end of the line for
clearance.

Step 4. Place temporary braces at intervals small enough
to hold the wall straight.

Step 5. Nail the brace when the wall is far enough away from the line to permit a 3/4-inch block to slide between the line and the plate.

BRACING

Bracing is used to stiffen
framed construction and make
it rigid. Bracing may be used to
resist winds, storms, twists, or
strains. Good bracing keeps
corners square and plumb.
Bracing prevents warping,
sagging, and shifting that
could otherwise distort the
frame and cause badly fitting
doors and windows and
cracked plaster. The three
methods commonly used to
brace frame structures are letin,
cut-in, and diagonal-
sheathing bracings (Figure 6-
40).

Let-In Bracing

Let-in bracing is set into the
edges of studs, flush with the
surface. The studs are always
cut to let in the braces; the
braces are never cut. Usually 1
x 4s or 1 x 6s are used, set
diagonally from top plates to
sole plates, or between top or
sole plates and framing studs.

Cut-In Bracing

Cut-in bracing is toenailed
between studs. It usually
consists of 2 x 4s cut at an
angle to permit toenailing.
They are inserted in diagonal
progression between studs
running up and down from
corner posts to the sill or plates.

Diagonal-Sheathing Bracing

The strongest type of bracing is diagonal sheathing. Each board braces the wall. If plywood sheathing 5/8 inch thick or more is used, other methods of bracing may be omitted.

EXTERIOR WALLS

The exterior surfaces of a building usually consist of vertical, horizontal, or diagonal sheathing and composition, sheet metal, or corrugated roofing. However, in TOs, those materials are not always available and substitutes must be provided. Concrete blocks, brick, stone rubble, metal, or earth may be substituted for wood in treeless regions. In the tropics, improvised siding and roofs can be made from bamboo and grasses. Roofing felt, sandwiched between two layers of light wire mesh, may serve for wall and roof materials where the climate is suitable. Refer to TMs 5-302-1 and 5-302-2 for details on substitute, expedient, and improvised construction.The following paragraphs cover the types of sheathing, siding, and building paper that may be used.

Sheathing

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

· Wood, 1 inch thick by 6, 8, 10, or 12 inches wide of No. 1 common square or matched-edge material.
· Gypsum board, 1/2 inch thick by 4 feet wide and 8 feet long.
· Fiberboard, 25/32 inch thick by 2 or 4 feet wide and 8, 9, 10, or 12 feet long.
· Plywood, 1/4, 3/8, 1/2, or 5/8 inches thick by 4 feet wide and 8, 9, 10, or 12 feet long.

Wood. Wood wall sheathing comes in almost all widths, lengths, and grades. However, it is normally 6 to 12 inches wide and 3/4 inch thick. Lengths are selected for economical use and the sheathing is either square- or matched-edge. Sheathing 6 or 8 inches wide should be nailed with two 8d nails at each stud crossing. Wider boards should be nailed with three 8d nails. It is laid on tight, with all joints made over the studs. It may be nailed on horizontally or diagonally (Figure 6-41); 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 a bottom corner of the building and work toward the opposite wall.

Gypsum Board. This type of sheathing is made by casting a gypsum core into a heavy, waterresistant, fibrous envelope. The long edges of the 4 x 8 boards are tongue and grooved. Each board is 1/2 inch thick. Gypsum board is generally used with wood siding. Gypsum board should be nailed with 13/4- or 2-inch galvanized roofing nails spaced 7 inches on center. Gypsum board can be nailed (together with the wood siding) directly to the studs (Figure 6-42). Gypsum sheathing is fireproof, water resistant, and windproof. It does not warp or absorb water and does not require the use of building paper.

Plywood. Plywood is highly
recommended for wall sheathing
(Figure 6-42). It adds a lot more
strength to the frame than using
diagonally applied wood boards.
When this sheathing is used,
corner bracing can be omitted.
For this reason and because of
their large size, weight, and
stability, plywood panels are
faster and easier to apply.
Plywood provides a tight, draftfree
installation of high
insulation value.

The minimum thickness of
plywood wall sheathing should
be 1/4 inch for 16-inch stud spacing, and 3/8 inch for 24-inch stud spacing. The panels should be installed with the face grain
parallel to the studs. A little more stiffness can be gained by installing them across the studs, but this requires more cutting and fitting. Use 6d common nails for 1/4-, 3/8-, and 1/2-inch panels. At the edges of the panels, space the nails not more than 6 inches on center; elsewhere, not more than 12 inches on center.

Siding

The siding for exterior walls should be decay-resistant, hold tight at the joints, and take and hold paint well.

Wood Siding. Wood siding should be decay-resistant, well-seasoned lumber. It should hold tight at the joints and take and hold paint well. It ranges from 1/2 to 3/4 inch thick by 12 inches wide.

Vertical Wood Siding. Vertical wood siding (Figure 6-43) 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.

Horizontal Wood Siding. Horizontal wood siding (Figure 6-43) is cut to various patterns and sizes to be used as the finished outside surface of a structure. There are two types beveled siding and drop siding (Figure 6-43).

Beveled. Beveled siding is made with beveled boards, thin at the top edge and thick at the butt. 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. Beveled siding is usually nailed at the butt edge, through the top edge of the board below. Very narrow siding is quite often nailed near its thin edge, like shingles. It is nailed to solid sheathing over which building paper has been attached. Window and door casings are first framed. The siding butts are put against the edges of these frames. Corners may be mitered, or the corner boards may first be nailed to the sheathing. Siding is then fitted against the edges.

Drop. Drop siding is used as a combination of sheathing and siding or with separate sheathing. It comes in a wide variety of face profiles and is either shiplapped or tongue and grooved. If used as a combined sheathing and siding material, tongue-and-groove lumber is nailed directly to the studs with the tongue up. When sheathing is not used, the door and window casings are set after the siding is up. If sheathing is first used and then building paper is added, drop siding is applied with beveled siding, after the window and door casings are in place.

Corrugated-Metal Siding. Corrugated metal is often used as wall cover since it requires little framing, time, and labor. It is applied vertically and nailed to girts. Nails are placed in the ridges. Sheathing can be used behind the iron with or without building paper. Since tar paper used behind metal will cause the metal to rust, a resin-sized paper should be used.

Vinyl and Aluminum Siding. Vinyl and aluminum sidings are popular, low-maintenance, low-cost wall covering. They can be backed with polystyrene or other board reinforcement, both to give the siding a strong base and an insulating R factor value.

Figure 6-44, page 6-34, shows the most common vinyl and aluminum sidings and installation accessories. Some variations exist between manufacturers, but the basic rules for installation are universal. They are--

· Nail in the center of slots.
· Do not nail tightly, leave loose for contracting and expanding.
· Leave at least 1/4-inch clearance at all stops.
· Do not stretch tight.
· Strap and shim all uneven walls.

Step 1. Place outside and inside corners with the bottom of the trim even with the area to weatherproof. Use a level or transit to maintain a constant horizontal line.

Step 2. Using a level, transit, or chalk line, place the bottom of the starter strip level with the bottom of the corner trim. The starter strip will butt the edge of the trim.

Step 3. Snap the bottom of the siding onto the starter strip and slide it tight into the corner trim, then out 1/4 inch to allow for expansion and contraction of materials in changing temperatures. Nail with roofing nails, 16 inches on center, in the center of the slot, without driving the nails home (leaving approximately 1/16 of an inch between the nailhead and the
wall sheathing).

Step 4. Attach additional pieces of siding in a like manner, except the additional pieces will be placed on top of earlier placed pieces (as top end and bottom ends, like male and female ends in tongue-and-groove materials). Lap tight, then pull away 1/4 inch.

NOTE: When ending a "run" into a corner or a J-channel, cut so that installation is 1/4 inch from butt to trim.

Step 5. Install J-channels on surfaces where the siding run breaks (as in a window or door). The J-channel provides a weatherproof surface.

On vertical breaks, butt the siding as described in the previous paragraph. On horizontal breaks, install the undersill trim inside the J-channel. The undersill trim is a fastening device. On surfaces such as the top of the door or window trim, this channel will hold pieces of siding that were cut (removing the part of siding that "snaps" onto the top of previous pieces) tight, keeping them from flapping in the breeze. On surfaces such as where the siding butts into the
soffit or below windows, a slotting tool is used to pierce the part of the siding that slides into the undersill trim. This pierce pushes out part of the siding and forms a catch. This is used when siding is pushed into the undersill trim, providing fastening for the top of a section of siding where nailing is not possible.

Building Paper

Building paper comes in several types. The most common type is resin-sized. It is generally red or buff in color (sometimes black). It comes in rolls, usually 36 inches wide; each roll containing 500 square feet and weighing 18 to 50 pounds. Normally, this building paper is not waterproof.

Another type is heavy paper saturated with a coal-tar product, sometimes called sheathing paper. This type is waterproof and insulates against heat and cold. In wood-frame buildings to be covered with siding, shingles, or iron, building paper is used to protect against heat, cold, or dampness. Building paper is applied horizontally from the bottom of the wall, and nailed with roofing nails at the laps. Overlapping the paper helps water runoff. Care must be taken not to tear the paper. The waterproof paper is also used in the built-up roof when the roof is nearly flat. Several layers are used, with tar between the layers.