Exterior walls

The exterior walls in most residential structures will be either wood frame or masonry, sometimes a combination of the two. The latter is commonly called a veneer wall. The exterior walls rest directly on the foundation and are bearing (load-supporting) walls. They support the roof, floors, and vertical loads imposed by other building components. The outer covering of the exterior walls provides protection from the weather and, if properly installed, minimizes the flow of air, moisture, and heat into or out of the structure.

When the walls are wood frame, the vertical framing members (studs) support all the vertical loads, and the outer finish covering (generally called siding) provides weather protection. Insulation is normally located in the spaces between the studs. In masonry walls, the masonry (clay tile, brick, stone, concrete block, etc.) provides both the structural support and the weather barrier. A masonry-veneer wall is a wood-frame wall with masonry used in place of the siding. Although the masonry in a veneer wall is not used for supporting the vertical loads, it does support its own weight.

Basically, a wood-frame exterior wall consists of 2-by-4-inch or 2-by-6-inch studs covered on the interior side by materials such as plaster, Sheetrock, plasterboard, wood, or hardboard panels (as described in chapter 10) and on the exterior side by sheathing, sheathing paper, and the finish siding. (See FIG. 5-1.) In some parts of the country where rot and termite activity are problems, metal studs are now being used in place of wood studs.

Sheathing is installed over the studs to provide bracing and minimize air infiltration. Depending on the type of sheathing, it can also be used to form a surface onto which the exterior finish can be nailed. Wood boards, plywood, fiberboard, and plasterboard are often used for wall sheathing. Fiberboard sheathing adds a small amount of insulation to the overall exterior wall; however, it should not be used as a nailing base for the direct attachment of the exterior siding. Rather, the siding should be nailed either to the studding through the sheathing or to wood nailing strips that have been attached to the sheathing. In many communities, when the exterior siding is capable of supplying adequate bracing and weather protection (as with exterior plywood panels), the sheathing is often omitted.

The purpose of the sheathing paper is to resist the direct entry of water during a

Metal Stud Partition Wall Construction
Fig. 5-1. Components of a wood-framed exterior wall.

driving rain. Sheathing paper (an asphalt-saturated felt) is water-resistant but not vapor-resistant and allows water vapor (which often builds up in the voids of the frame wall) to escape rather than condense and cause problems. Sheathing paper can also be very effective in reducing air infiltration.

Exterior siding

There are many types of exterior siding. If the siding is of good quality and has been maintained, it could last as long as the house. Normally, the type of maintenance required (other than painting) is the repair of cracked, broken, loose, rotting, or missing sections. When maintenance is needed, it is usually on a small section rather than the entire wall. However, some homeowners neglect the siding and allow it to deteriorate to a point where complete re-siding is necessary. Several clients have asked me about the condition of the old siding on a house that had been re-sided. Actually, the degree of deterioration of the old siding does not matter as long as the new siding is properly installed and provides the needed weather protection.

When inspecting the siding, pay particular attention to the sections that are facing south or southwesterly. These areas receive the maximum exposure to the sun and are more vulnerable to weather deterioration. The bottom of exterior siding should not be close to, or in contact with, the ground. Because of the dampness associated with the ground, the bottom of the siding should be at least 8 inches above the finished grade. Otherwise, the wood siding or the wood nailing boards for nonwood siding will be vulnerable to rot and termite infestation.

On occasion I have found vines growing up an exterior wall, in some cases reaching the roof. Although this might be aesthetically pleasing, the vines are undesirable. They can cover a multitude of problems and can cause problems. The vines can conceal termite shelter tubes (see chapter 8) or cracked portions of the siding. They can widen cracks, damage mortar joints, and loosen shingles. In addition, the dampness associated with the vines can promote rot and cause paint to blister and peel. If you find vines growing up an exterior wall, you should consider removing them.

Wood siding Wood siding is a broad classification that includes shingles, shakes, boards (applied vertically and horizontally), plywood panels, and hardboard. When inspecting wood siding, pay particular attention to exterior corner joints and the joints between the siding and window frames and doorframes. In addition, the area where the siding joins a dissimilar material (such as masonry or metal) is vulnerable to water penetration during a driving rain. These areas should be checked for weathertightness and rot.

On wood siding you might find dark, blotchy sections. This condition is generally caused by spores of fungi or mildew and often occurs in shaded areas. It is not a concern because it does not cause the siding to decay. However, it is unsightly. On painted surfaces, it can often be removed by washing with bleach and water. New paint on such areas should contain a mildew-inhibitor additive. On unpainted wood surfaces, this condition can usually be controlled by coating the siding with a penetrating preservative containing a mildewcide. You might also find brown and black discolorations on the siding (FIG. 5-2). This staining is caused by rusting of the nails used to secure the siding. The discolorations could have been avoided if aluminum or galvanized (rust-resistant) nails had been used. Eliminating this condition is somewhat difficult and usually not cost-justified.

Wood shingles/shakes Most shingles and shakes (hereafter referred to as shingles) used

Fig. 5-2. Discolorations of wood shingles caused by rust stains from iron nails.

for exterior sidewall application are made from cedar or redwood. They are basically the same ones that are used for roofing (as described in chapter 2). However, their application is somewhat different. Because vertical walls present fewer water-penetration problems than roofs, the shingles on walls can be installed with a greater weather exposure than those on roofs. In addition, roofs generally have a three-ply layer of shingles, whereas exterior walls have only a two-ply layer. For full weather protection, the butt joints between the wall shingles for the upper ply should not line up with the vertical joints for the lower ply. Otherwise, water can penetrate the wall during a driving rain.

Since the shingles are decay-resistant, they do not have to be painted for weather protection. However, new shingles that replace deteriorated unpainted weathered shingles will not match the remaining shingles. Many shingles are painted to achieve a color decor. After a number of years, the paint begins to peel and flake. Consequently, once the shingles are painted, they will require periodic repainting for cosmetic purposes.

When inspecting the shingles, look for cracked, loose, chipped, rotting, and missing sections. Inspect for warped shingles; they generally will be on the sidewall with the southerly or southwesterly exposure. Also look at the quality of the shingles. You might find that the top portions of some are paper thin and can crack or chip very easily. These shingles are of a lower quality and are intended for use as an undercourse or installation with less shingle-length exposure. This type of shingled sidewall has a short projected life, and periodic repairs, with eventual residing, should be anticipated. Try to lift a few shingles gently. They should not lift up. If they do, it is an indication that they were improperly nailed. Shingles that are nailed directly to fiberboard sheathing rather than to wooden nailing strips (attached to the sheathing) will lift up under gentle pressure. Any of the above conditions should be recorded on your worksheet for future correction.

Wood boards Wood-board siding can be applied horizontally or vertically. Horizontal siding tends to make a house appear lower and longer; vertical siding tends to make a house appear taller (and is popular on one-story houses). The wood used for board siding should be free of knots. Otherwise, over a period of time, shrinkage can cause the knotty cores to drop out, leaving the siding with holes that are vulnerable to water penetration.

With the exception of redwood and cedar boards, most wood siding is painted for protection against weathering and decay. When inspecting the siding, look at the condition of the paint. Are there any bare, peeling, flaking, or blistered sections? If there are, paint touchup or repainting may be needed. Blistered and peeling paint is often caused by moisture in the painted wood, although it can also result from a poor paint job. Determination of the exact cause for blistering and peeling paint cannot be made during a single inspection. Nevertheless, this condition should not affect your thinking about the house. If it is caused by moisture in the wood, it can be corrected after you move in, and usually at minimal expense.

Wood-board siding should be inspected for cracked, loose, and rotting sections. In addition, look for loose or missing knots. All holes should be patched with a wood filler. In vertical siding, check the joints between the vertical sections for weathertightness. In both vertical and horizontal siding, pay particular attention to the outside corner joints. These joints are vulnerable to water penetration during a rain, and any open joints must be sealed.

Plywood panels Plywood panels are also used for siding. They are made from exterior-type plywood in which the veneer layers are bonded together with a waterproof glue. The exterior facing of the panel comes in a variety of surface textures and grooves. The panels are 4 feet wide by 8, 9, or 10 feet long. The thickness of the panel will depend on the depth of the grooves and will generally vary between % and % inch. Plywood panels are usually installed in a vertical position with the vertical joints over studs. This minimizes the number of horizontal joints, which is desirable since plywood panels are often applied directly to the studs rather than over sheathing. Because of their vulnerability to water penetration, any horizontal joints should be shiplapped (not visible to the inspector) or protected by metal flashing (visible). When inspecting plywood siding, look for loose, warped, cracked, delaminated, and rotting sections. Also check for open and nonweathertight joints. If the panel siding is painted, check the finish for peeling and flaking paint and blistered sections.

Hardboard siding Hardboard siding is made by bonding (under heat and pressure) wood fibers that have been ground almost to a pulp. The siding is dense and tough, and has a fairly good dimensional stability, although not as good as that of plywood. Hardboard, like plywood, is available in a wide range of textures and surface treatments. It is available in 4-foot-wide panels and 9- and 12-inch-wide planks. When inspecting hardboard siding, look for cracked, chipped, broken, deteriorated, and loose sections. Also check horizontal and vertical joints for weathertightness.

Aluminum siding Aluminum siding is often used in new construction and is often used when re-siding the exterior walls. The siding comes in planks that are either smooth or embossed with a wood-grain texture (to resemble painted wood boards), also as shingles and vertical panels. Aluminum siding is relatively maintenance-free. It is noncorrosive and termite-proof, and will not rot. The siding surface is generally covered with a baked enamel-paint finish that can stand up for many years before it fades, becomes dull, and needs a coat of paint. If the siding is scratched, bare aluminum is exposed. However, since the aluminum does not corrode, the scratch is only of cosmetic concern and can easily be corrected with touch-up paint. One problem with the siding is that it can be dented if struck hard enough— as with a baseball or stone thrown from a power mower. Many communities require that aluminum siding be grounded electrically as a precaution against electrical shock.

Aluminum siding is available with or without insulation backer boards. The insulation is generally a rigid foam (such as polystyrene) or fiberboard. Although the backer boards are only about % inch thick, they are quite effective as an insulator for a house that has no insulation in the exterior walls. Because of increasing energy costs, even a house with insulation in the exterior walls benefits from the additional insulation. The backer boards reduce heat loss in the winter and heat gain in the summer. They also increase the strength and rigidity of the siding. However, insulation-backed siding (and tight siding jobs) can cause moisture to accumulate within the exterior walls of houses that have no vapor barriers on the inside surface. (Insulation and vapor barriers are discussed in chapter 19.) You can usually tell whether the aluminum siding has an insulation backer board by pressing on it. If the siding is relatively firm, it has a backer board, but if it yields and bends under the pressure, it has no insulation board. Another method is to tap the siding. If it has no insulation, you will get a hollow sound.

When inspecting aluminum siding, look for loose, missing, and dented sections. Check the exterior joints for open sections and weathertightness. In those areas where electrical grounding of the siding is required, you should look for an electrical ground connection, a wire that runs from the siding to the inlet water pipe or a rod or pipe that has been driven into the ground. (See chapter 12.) You can find out whether an electrical ground connection is required by checking with the local municipal building department.

Vinyl siding Vinyl siding is very much like aluminum siding in size, shape, application, and appearance. Quite often close examination of the siding is needed to tell the difference between the two. The coloring in vinyl siding is embedded in the material and is the same throughout its thickness. Since the coloring in aluminum siding is only on the surface, an end cut or scratch in the aluminum reveals the silvery color of the bare metal. To tell whether the siding is vinyl or aluminum, look at an end cut or joint.

Vinyl siding is usually installed with an insulation backer board behind each sheet. In addition to insulation value, the board adds rigidity and strength. Vinyl siding normally does not dent from impact; it merely flexes and springs back to its original shape. However, during very cold weather, the siding becomes brittle, and a hard blow could crack or shatter it. When inspecting vinyl siding, check for cracked and broken sections and loose and sagging sections with open joints.

Vinyl siding expands and contracts as the temperature changes. When the siding is improperly nailed, this movement usually results in waviness and blisters in the vinyl panels. If you see this type of unevenness in the vinyl panels, record the fact on your worksheets for future correction.

Asbestos-cement shingles As with roofing shingles, asbestos-cement siding shingles were manufactured by combining asbestos fibers with Portland cement under pressure. These shingles are currently called mineral-fiber shingles. Although the shingles are no longer manufactured, they can be found on many homes in a variety of textures and colors. Since the shingles are unaffected by the weather and are immune to rot and termite activity, they require very little maintenance. However, the shingles are brittle and can be damaged and cracked by impact. The lower courses of the shingles are most vulnerable to damage. Usually damaged shingles are replaced rather than repaired. When inspecting asbestos shingle siding, look for cracked, chipped, broken, loose, and missing shingles. Shingles that have slipped out of place were usually improperly nailed, or the nails were not rust-resistant and deteriorated. If the condition is caused by the latter, additional shingles will slip out of place in the future, and maintenance should be anticipated.

Asbestos-cement shingles were generally installed with sheathing-paper-backer strips behind the vertical shingle joints. These backer strips provided additional protection against water penetration. You might find sections of backer strips that have slipped out of place or are hanging loose between the shingles. Since the shingles were normally installed over sheathing paper, which is waterproof, replacing the loose backer strips is usually not necessary.

Asphalt siding Asphalt siding is made by impregnating an organic felt material or glassfiber mat with asphalt. The siding is available as shingles or as a roll. The exterior surface of the roll material is coated and embossed so that from a distance it looks like bricks. As the siding ages, it becomes dry and brittle, and cracks easily. For the most part, asphalt materials are no longer used for siding or residing residential structures. However, they can be found on existing buildings. When inspecting asphalt siding look for cracked, chipped, and eroded sections. Also check for open and lifting joints and loose, torn, and missing sections. If you find any areas in need of repair or replacement, record them on your worksheet.

Stucco A stucco finish on an exterior wall is basically a concrete sheet that has been built up in layers. It is usually made from a mixture of cement, lime, sand, and water. Stucco is weather-resistant, immune to termite and fungus attack, rigid, and durable—qualities that are desirable for an exterior wall finish. In addition, it can be applied to curved or irregularly shaped surfaces and to wood-frame walls that have been prepared with backing (sheathing) paper and metal lath. The backing paper is needed to resist water penetration through open joints or cracks that might develop in the stucco. The metal lath provides the means for bonding the stucco mix.

Stucco is generally applied in two coats on a masonry wall and three coats on a woodframe wall. The minimum thickness for a three-coat wall is 78 inch; for a two-coat wall, % inch. The top layer of stucco is the finish coat and can be relatively smooth or have a rough texture. It can be prepared in a wide range of colors or painted.

Because stucco is a rigid material, cracks can develop as a result of a slight movement of the house. (See FIG. 5-3.) Movement occurs

Calliandra Vine Stucco Wall
Fig. 5-3. Cracked stucco wall. If wall was covered with vines, these cracks would be concealed.

from foundation settlement and from wind forces. You generally find more cracks in stucco on a wood-frame house than on a solid masonry house. Shrinkage of the wood-framing members creates stresses in the stucco that often result in cracks. Once a crack develops, water can penetrate into the wall during a driving rain and can cause problems. In time, the portion of the metal lath around the crack rusts and deteriorates, and, depending on the condition of the backing paper, the wood framing and sheathing might rot. In addition, in cold climates, accumulated water behind the stucco can freeze, causing further deterioration as a result of frost action.

All cracks should be sealed. Hairline cracks and cracks up to X6 inch generally can be sealed by coating them with a cement-based paint. The only difficulty is in matching the color of the wall. Larger cracks can be sealed by filling them with a mortar mix. Broken and loose sections of stucco must be rehabilitated by a skilled craftsman. When inspecting a stucco wall, look for chipped, cracked, loose, and broken sections. If you find areas in need of repair, record their location on your worksheet. Stucco does not require painting. But if it has been painted, check the condition of the paint. Once a stucco wall has been painted, periodic repainting will be required for cosmetic purposes, although at less frequent intervals than wood.

Synthetic stucco Synthetic stucco, commonly known as an exterior insulation and finish system (EIFS), is an exterior wall siding that consists of four primary components:

• Foam insulation boards attached to the exterior wall sheathing

• A base coat that is applied to the insulation board

• A fiberglass reinforcing mesh embedded in the base coat

• A finish coat applied over the fiber glass mesh

Although the EIFS may resemble stucco in appearance, the two siding systems are quite different, especially with regard to controlling water intrusion. The traditional stucco system anticipates eventual water penetration through open joints and cracks. To prevent rot and deterioration of the wood framing and sheathing in the exterior walls, it uses a housewrap or building paper behind the stucco surface to carry any water that accumulates in that area down and out the bottom of the wall.

The EIFS, on the other hand, was not designed for water intrusion. It was considered a surface barrier system because it resisted water penetration at its outer surface. It was assumed that moisture would not penetrate the surface and reach the wall sheathing and/or framing. The system was not originally intended to drain water that got behind the EIFS cladding. In practice, however, water did penetrate the wall, not through the surface but through jambs and sills of window frames, and at the joints between the exterior walls and door, window, deck, and roof intersections. Water that penetrated the wall could not easily escape. It was trapped between the EIFS cladding and the sheathing.

Over a period of time the water was absorbed by the sheathing and framing, which increased their moisture content to a level above saturation, causing rot and structural damage. Depending on weather conditions and the quality of construction, significant damage due to moisture intrusion could occur. Damage from water intrusion has been found in the exterior walls of houses that are only 3 to 5 years old.

The industry, recognizing the problems that resulted because of the lack of drainage in the wall, modified the system to include the installation of drainage channels and building paper between the foam insulation and the sheathing. In appearance the new system is similar to the old one, and with a visual inspection you cannot tell the difference between the drainable and nondrainable EIFS. Not only is the location of water entry often difficult to see, but moisture damage to the sheathing and framing behind the exterior wall cladding cannot be readily detected by visual inspection.

If the exterior wall cladding is an EIFS, you can do a preliminary inspection by checking for cracked and open joints at the interfaces between the EIFS and dissimilar materials such as windows, doors, and wall penetrations. If any are found that require caulking, record their location on your worksheet. Also, if you have a noninvasive moisture meter, check those areas for water intrusion. However, because of the nature of the potential problems and the high cost for correction, it is recommended that you have the exterior walls inspected and evaluated by a professional.

Veneer wall A veneer wall is a woodframe wall with an attached masonry facing. Unlike exterior siding, which is held in position by being fastened to the sheathing or studs, the masonry rests on top of the foundation wall and supports its own weight. It is attached to the wood backing by corrosion-resistant metal ties. The ties are considered the weakest point in this type of construction. If the ties have deteriorated or are not properly attached, the masonry facing can pull away from the wood frame.

The masonry—usually clay brick, concrete brick, or split stone—is normally positioned so that there is a 1-inch air space between the veneer wall and the wood backing. (See FIG. 5-4.) Small holes (weep holes) are usually installed at the base of a veneer wall. These holes allow water that might accumulate in the air space to drain. When the masonry facing is brick, the weep holes are generally formed by eliminating the mortar in a vertical joint.

Some bricks absorb more water than others. Bricks with high absorption should not be used for the exterior facing of walls, especially in colder climates. Unfortunately, they are used occasionally. Alternate freezing and thawing of bricks that have absorbed water will cause them to deteriorate. Depending on how much water has been absorbed, the interior walls might become damp, a condition that can usually be detected during the interior inspection. This condition can often be controlled by coating the bricks with a silicone sealant.

When inspecting a veneer wall, look for chipped, cracked, loose, deteriorating, and missing bricks or stones. In addition, check for cracked, chipped, and deteriorating mortar joints. Pay particular attention to the mortar

Masonry veneer Fig. 5-4. Components of a brick-veneered exterior wall.

joints. Occasionally, because of excessive shrinkage of the wood framing or slight foundation settlement, you might find large open cracks, especially around window frames and doorframes. Also look for loose and bulging sections of veneer wall. If you find any of the above items, record their location on your worksheet for later correction.

Masonry wall

Unlike a wood-frame wall where the structural support and weather barrier are provided by two separate components, studs and siding, the masonry units in a masonry wall (clay tile, brick, stone, or concrete block) provide both the support and the weather protection. Because of the low thermal resistance of masonry, a masonry wall allows greater heat loss than a wood-frame wall.

To reduce the heat loss, insulation can be added by applying a rigid foam insulation board to the interior side. In addition to providing insulation, the board can also be used as a base for plastering. Another approach is to apply furring strips to the inside wall; the furring strips create an airspace into which insulation can be placed prior to installing the finishing wall panel. In some cases, however, the interior side of the masonry wall is left completely exposed and serves as a decorative element or a base for direct plastering. This is quite wasteful from an energy-conservation point of view.

Because of the rigidity of masonry walls, differential movement within the wall might cause serious cracking. Wall movement might be the result of unequal foundation settlement, or expansion and contraction from temperature and humidity changes. Many cracks are not of structural concern, although they should be sealed to eliminate the possibility of water penetration. If you have any doubt about the severity of a crack, have the condition checked by a professional.

A common problem with masonry walls is efflorescence on the exterior surface. Efflorescence is a deposit of soluble salts that were originally within the masonry, usually brought to the surface by water in the wall. When the water evaporates, the salts are deposited on the surface. Efflorescence generally can be removed by scrubbing with a stiff brush or washing with a dilute solution of muriatic acid. However, if the condition is a recurring problem, it is an indication that water is penetrating the wall through cracks or faulty joints or flashing.

When inspecting a masonry wall, pay particular attention to the joints around window and doorframes. All joints should be weathertight. Are there any cracks around the corners of window or door openings? These are areas of high stress concentration and are vulnerable to cracking. Cracked and chipped mortar joints and deteriorated masonry should be indicated on your worksheet for later repair. If you notice bulging sections in the exterior walls or large cracked sections, have the condition checked professionally, since it might indicate structural problems.

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