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P A R T
O N E
EXTERIOR CLADDING The exterior surfaces form the skin of the house, and are referred to as cladding. Cladding components include— I
wall surfaces
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soffits and fascia
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windows and doors
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trim, flashings, and caulking
There are many different styles and materials in exterior cladding. You will learn how to recognize each of these materials, how they tend to fail, and what to advise your client. We We will also discuss tips and techniques for inspecting cladding. Some issues related to siding are not covered in detail in this part because— I
they are not usually accessible for inspection
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there are different requirements among various siding products, jurisdictions, jurisdictions, and manufacturers
You may want to research your local requirements for each siding material.
1
C H A P T E R
AN OVERVIEW OF WALL SURFACES L E AR N I NG
O B JE C TI V E S
By the end of this chapter you should know: I
ten types of exterior siding material
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six components of a typical wall assembly
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four common problems that crop up on any exterior wall system
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Part I
Exterior Cladding
I N T R O D U C T I O N
In this chapter we are going to look at exterior wall surfaces, including several types of cladding. Our discussions here are focused on weather-tightness. We think of the exterior as a weather-tight skin for the building.
1.1 MATERIALS AND CHARACTERISTICS There are many siding materials, including—
Ideal Wall Claddings
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masonry products such as brick, stone, poured concrete, and concrete block
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poured concrete
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stucco (either over wood frame or masonry)
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synthetic stucco (EIFS, or Exterior Insulation and Finish Systems)
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wood products, including shingles and shakes, plank siding, plywood, OSB, and hardboard
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metal products, including steel and aluminum
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vinyl
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asphalt shingles
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slate and clay tiles
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fiber-cement
The best wall systems are highly resistant to water, wind, mechanical damage, and vermin entry. They are inexpensive, easy to install, and low maintenance, have great cosmetic appeal, and provide good security. They also provide thermal insulation and have a long life expectancy. Most sidings do only some of these things well. There are no perfect siding materials. Table 1.1 summarizes the characteristics of some common wall coverings.
1.2 WALL ASSEMBLIES Before we look at individual sidings, let’s briefly review typical wall assemblies (Figure 1.1). These include—
Structural Members
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structural members—studs or masonry, for example
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interior finishes—plaster or drywall, typically
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insulation and an air/vapor barrier (usually on the interior side of the insulation)
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sheathing—wood plank, plywood, board, etc.
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building paper or housewrap
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siding
OSB,
fiberboard, gypsum board, cement
Structural members include wood frame and masonry walls. These are designed to carry the live and dead loads from floors and roofs. They are also designed to carry the dead load of the siding and the live load of wind. We don’t get to see much of the wall structure during an inspection.
T A B L E
1.1
Surface Type
Characteristics of Various Wall Surfaces Weather-Tight (Water, Snow, Wind)
Strength (Resistance to Mechanical Damage)
Structural Properties (Capable of Carrying Loads)
Cost
Insulating Value
Maintenance Requirements
Most Common Failure Modes
Brick Stone Concrete
• Varies • Brick is porous
Good
Yes
High
Poor
Low, unless painted
• Spalling • Cracking • Missing mortar
Stucco
Good, but vulnerable at joints
Fair
No
Medium
Poor • EIFS is good
Low, unless painted
• Cracking, bulging • Allowing water into walls • Coming off in sheets
Wood Shingles and Shakes
Good
Fair
No
Medium
Poor
Low, unless painted or stained
• Rot, splits • Cupping, curling • Burn-through
Wood Siding (Clapboard, etc.)
Good
Fair
No
Medium
Poor
High, unless unpainted or unstained
• Rot • Cracking
Vinyl
Good
Fair to poor
No
Low
Poor
Low
• Mechanical damage • Loose and missing pieces
Metal (Aluminum and Steel)
Good
Fair to poor
No
Low
Poor (insulated metal slightly better)
Low
• Denting • Loose and missing pieces
Asphalt Shingles
Good
Poor
No
Low
Poor
Low
• Tearing • Curling • Surface wearing off
Slate, Clay Tiles
Good
Good
No
High
Poor
Low
• Pieces breaking off or slipping out of place
Fiber Cement
Good
Good
No
Medium
Poor
Low
• Pieces breaking off or slipping out of place
Plywood
Good, but vulnerable at joints
Fair
No
Low
Poor
High
• Needs regular painting or staining
Hardboard and OSB
• Fair • Joints/edges vulnerable • May swell
Fair
No
Low
Poor
Low to High • Needs regular painting or staining unless prefinished
• Rot • Swelling • Fungus • Cracking
C h a p t e r 1
A n O v e r v i e w o f W a l l S u r f a c e s
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Part I
F I G U R E
Exterior Cladding 1.1
Wall Assemblies Structural members (studs in this case) Insulation Sheathing (e.g., plywood) Vapor barrier (interior side of insulation in cooler climates)
Building paper or housewrap
Interior finish (e.g., drywall)
Siding
n t io a d un o F Flashing Sill gasket
Interior Finishes
Insulation and Air/Vapor Barriers
Sheathing
Insulating Sheathing Building Paper or Sheathing Paper
Interior finishes are largely cosmetic and provide the base for the interior decoration. They also help to separate the indoor environment from the outdoor environment by restricting air movement through the wall. Insulation and air/vapor barriers are more important in cold climates than in warm climates, although they are found in most areas. The insulation can be between the studs in a wood frame wall, or it can be mounted on either side of the wall structure behind exterior or interior finishes. The amounts of insulation installed vary depending on the climate, the local building requirements, and the builder’s or homeowner’s commitment to energy conservation and low energy costs. Again, we don’t get to see much of the insulation or air/ vapor barrier. Many older homes have no insulation or air/vapor barrier in the walls. Sheathing has traditionally been provided on the exterior of wood frame walls. It adds rigidity to the structure to help prevent racking. Many modern buildings do not rely on sheathing to prevent racking, since most interior finishes provide adequate rigidity. Sheathings provide a substrate for building paper and help to reduce air movement through the wall assemblies. Many sheathings are vapor permeable or have loose fit joints, so they won’t trap moisture moving out through the wall. Moisture is carried through walls by the air that leaks through and by vapor diffusion (no air movement needed). The air-transported moisture is the more important of these two mechanisms. Some sheathings are rigid insulation board. Their primary function is to control heat loss. The functions of building paper (also called building felts or sheathing paper) include— I
protecting the wall from water that gets past the siding
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helping to prevent wind blowing into the wall system, which would reduce the effectiveness of the insulation
Chapter 1 I
Not Always Required
Housewrap
Siding Connectors
Masonry Ties Stucco Support for Siding
F I G U R E
1.2
An Overview of Wall Surfaces
11
allowing vapor moving through the wall from indoors to escape to the exterior (building paper must breathe)
Sheathing paper may not be required under hardboard, plywood, fiber-cement, synthetic stucco, or metal siding where all joints are protected against wind and water penetration. Some argue that there are very few systems that provide 100 percent protection, especially at joints, against wind and water penetration. Those people maintain that sheathing paper should be provided in all cases: the sheathing paper provides a backup or second line of defense against moisture penetration. Building paper is, in many areas, being largely replaced by housewraps. These are typically spun polyolefin fabrics that are designed to protect against water that gets through the siding and against wind blowing into the wall system. Proponents of housewraps maintain that these are more effective than building paper. Housewraps also need to be breathable so that vapor moving out through the wall system won’t be trapped and condense in the wall assembly. Again, in most cases, we won’t be able to see whether building paper or housewrap was used behind the siding. Many sidings, including wood, metal, vinyl, slate, asphalt, clay, and fibercement, are usually held in place with nails. Siding is typically attached through the building paper and sheathing to structural members, such as studs. Most sheathings are not strong enough to support the siding itself with conventional fasteners. There are exceptions to this. Masonry veneer sidings are held against walls with metal ties. These ties have several different shapes and sizes. Stucco is typically held in place with wire mesh that is nailed through building paper and sheathing. Some wall surface systems must rest on the building foundations and footings because of their weight (Figure 1.2). These heavier systems include stone, concrete, concrete block, and brick. Lighter sidings are hung on the building frame.
Support for Siding
Sheathing
Brick ties are for lateral support only
Building paper
Masonry veneer
Sheathing Wire lath
Joist
o c c u t S
Foundation
Joist
Foundation
Flashing Drip screed Heavy sidings (brick, stone, concrete) must be supported on foundations and footings
Lighter sidings can be supported by the building frame
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Part I
Exterior Cladding
1.3 GENERAL STRATEGY Now, let’s look at some of the issues that apply to all types of wall surfaces. They include— 1. Water penetration 2. Too close to grade 3. Too close to roofs 4. Planters and gardens against the wall 5. Vines 6. Insulation problems
1.3.1 Water Penetration CAUSES
Condensation
IMPLICATIONS
Concealed Damage
F I G U R E
1.3
Most serious wall problems are related to water in one way or another. Rainwater may enter wall systems in several ways. It may be driven by wind or it may enter by gravity or by capillary action. Water may also be a problem in wall systems if warm, moist air moving through the wall (from indoors in cold weather and from outdoors in warm weather) is cooled and deposits condensation inside the wall system (Figure 1.3). Smaller amounts of condensation may also form if moisture moves into the walls by vapor diffusion. You should watch for water damage to wall systems, although in many cases you won’t be able to see it. If the siding is deteriorating, there is a good chance
Condensation in Walls Outside
Inside
Insulation
Drywall
Warm, moist air
Exterior sheathing
Outside
Cool air
Cool air
Condensation
Floor framing
Warm, moist air
Condensation
Floor framing
Summer
Cross section
Inside
Winter
Siding, vapor barrier, and sheathing paper not shown
Chapter 1
Drying Potential
STRATEGY
An Overview of Wall Surfaces
13
that there is some damage behind it. However, in many cases (e.g., metal or vinyl siding and synthetic stucco) the siding looks fine while the sheathing and wall structure behind are deteriorating. The ability of a wall system to dry often determines the amount of damage done to the cladding and the structure. Wall systems with sidings with good drying potential, such as aluminum or vinyl, may be less likely to suffer damage than synthetic stucco, for example, which has poor drying potential. As you look at exterior wall surfaces, look first at the cladding materials and see if they’re in good repair. Second, try to determine how water might get into the wall system and whether there are any areas where you might reasonably suspect concealed damage. Your inspection of the inside of the building should focus on the vulnerable areas that you noticed outside. In some cases, the water getting into the wall system will show up on interior finishes, allowing you to confirm your suspicions. However, damage to wall assemblies doesn’t always show up on the building interior, at least not in the early stages. Pay attention to the drying potential of the wall system. Brick veneer systems with vented rain screens have good drying potential, whereas most stucco systems do not.
1.3.2 Too Close to Grade Wall cladding materials should be 6 to 8 inches above grade to protect the cladding system and the structure from water damage (Figure 1.4). This means that we can see some of the foundations above grade and below the siding. Foundations are designed to withstand the moisture in the soil. People may not like the appearance of exposed foundations, but from a functional standpoint, we want to see them.
F I G U R E
1.4
Too Close to Grade
Wall framing
8" minimum clearance for siding and stucco 6" minimum clearance for masonry
Floor framing
Foundation wall
S l o p e f o r d r a i n a g e
Finish grade Building paper not shown
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Part I
Exterior Cladding
Masonry
Other Sidings CAUSES
IMPLICATIONS
Weep Holes Covered
STRATEGY
The Worst Case
A Better Case
Masonry should usually be at least 6 inches above grade. There are exceptions because some bricks, for example, are designed for use at and below grade. You’ll be able to tell on older buildings whether the brick was designed for use below grade by looking for damage. On new homes, it’s hard to know. You should describe any new brick within 6 inches of grade as suspect, but allow for the possibility that it may be the correct type. Most other sidings, including wood and wood-based products, stucco, fibercement, metal, and vinyl, should be at least 8 inches above grade. Siding materials too close to grade are typically the result of— I
poor original construction and landscaping
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grade levels altered during landscaping or surface water control work
It’s possible that the siding is too close to grade because the building is settling, but there are bigger problems if this is the case. It’s easy to recognize the damage to the wall cladding materials. This may include— I
spalling (crumbling or flaking) and cracked brick and missing mortar
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obstructed weep holes in masonry veneer
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rotted wood
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swollen, buckled, or cracking wood-based products
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peeling paint
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staining
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rusted fasteners
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rusted lath and drip screed on stucco
In some cases, veneer walls with weep holes and flashings along the bottom course suffer dramatically if the weep holes are below grade (Figure 1.5). Water won’t be able to drain out, air won’t be able to get in, and moisture may seep from the soil into the building through weep holes. Severe spalling can occur. The more serious and concealed implications are the damage to the wall and floor structures behind the siding. This includes rot and insect damage at sheathing, studs, sill plates, headers, and floor joists. Damage to interior finishes and components is also possible. Sometimes damage is not visible until it is serious. This may be the first indication that there is a problem. Check around the building perimeter for adequate clearance between siding and grade. Can you see part of the foundation? Where the siding is below or too close to grade, look first for damaged siding. If possible, probe to look for damage to the structural members behind. Note the areas where siding is too close to grade and check inside the building for evidence of water leakage and damage. Try to find the top of the foundation wall. How far above grade is the top of the wall? The foundation wall may be too short to allow the siding to end 6 to 8 inches above grade. This is the more serious situation. We can’t remove soil and create a trench around the house because we’ll have a chronic flooding problem as surface water is funneled against the house. The foundation is ideally raised to solve the problem, but this can be very disruptive and expensive. If the siding is too close to grade because the grade has been elevated to form a garden, for example, the solution may be to restore grade level to its original position. This is less disruptive and expensive.
Chapter 1 F I G U R E
1.5
An Overview of Wall Surfaces
15
Weep Holes below Grade Masonry veneer Stud wall
W a te r
Wood gets wet and rots
Gr ad e l ev e l
Water gets in and air can’t get out
Joist
Weep hole Foundation
Cross section
Another Better Case Masonry Veneer Walls
If the siding has simply been installed too low, the solution may be to remove the bottom few inches of siding. This is only practical if the foundation is tall enough. Masonry veneer walls typically have weep holes and flashings near the bottom of the wall. Look to see if these have been buried. There should be a weep hole (missing vertical mortar joint) about every fourth brick along or near the bottom of the wall. Buried weep holes can lead to considerable damage to the brick veneer and the structure.
1.3.3 Too Close to Roofs
CAUSES
IMPLICATIONS
Siding materials should not be chronically wet. We’ve talked about this with respect to grade level. It’s also true where the bottom of the siding intersects a roof (Figure 1.6). The best practice is to keep the siding material 2 inches above the roof. Most people settle for a 1-inch clearance. There are step flashings under the siding and roof, so it’s okay to keep the siding above the roof surface. Wood and wood-based products are particularly vulnerable to moisture wicking up into and damaging the siding. End grains of wood and cut edges of hardboard, OSB , and plywood draw moisture into the wood enthusiastically. It’s common to see siding deterioration along a roof/wall intersection. Again, water damage to the siding and possibly to the structure behind are the implications. Most sidings discolor if they are chronically wet. Paint may peel. Stucco may soften and crumble. Brick may crack and spall, especially if the moisture in the brick freezes. Efflorescence may develop on the brick.
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Part I
F I G U R E
Exterior Cladding 1.6
Siding Too Close to Roof
Siding should have 1" (preferably 2") clearance from roof shingles to prevent water damage
Metal step flashings
F I G U R E
1.7
Watch for Planters or Gardens Against Walls
Planter raises soil level next to house
Watering and rain
Brick veneer Wall framing Rot Floor framing
Water infiltration
Spalling
Topsoil Foundation wall
Backfill
Basement Cross section
STRATEGY
Look for a 1- to 2-inch separation of siding and roofing materials. Where there is little or no clearance, look and probe for deteriorated siding materials.
1.3.4 Planters or Gardens Gardens should not be built against houses such that earth is held against the siding (Figure 1.7). A raised planter with three sides and the building acting as the fourth
Chapter 1
CAUSE IMPLICATIONS STRATEGY
An Overview of Wall Surfaces
17
side is a poor arrangement. Siding materials are not designed to be in contact with earth. The situation is worsened when people water their gardens and the soil is perpetually damp. Planters and gardens against siding are a landscaping problem. The implications are damage to the siding and wall structure behind and below. Look for siding to be 6 to 8 inches above exterior grade. If the siding itself is susceptible to water damage, it should be 8 inches above grade. Where you see raised gardens or planters, look for evidence of damage to the siding on the outside and look for evidence of water penetration and damage on the interior. Raised planters close to buildings should have four sides and should be set out roughly 2 inches from the siding. This is not a common detail, but it’s a lot easier on the building.
1.3.5 Vines
Better on Masonry
Inspection Limitation CAUSE IMPLICATIONS
STRATEGY
Several types of vines and ivies grow on buildings. Some do more damage than others. All tend to hold moisture against walls and trim. All provide pest entry opportunities. Many people are prepared to live with these disadvantages to enjoy the cosmetic effect. Masonry walls are more tolerant of vines than is wood siding. Vines should be kept away from all wood trim, including doors, windows, soffits, fascia, and gutters. Vines should be kept off aluminum siding. A wall covered with vines cannot be fully inspected. This includes the trim, soffit, and fascia. This limitation should be noted in the report. Vines are generally grown intentionally by the homeowner. As discussed, the implications may include insect and pest entry and moisture deterioration to the wall because of slow drying. In severe cases, depending on the type of vines, root systems or attachment nodes can damage siding or enter the building, often through trim areas, providing a direct path for water into the building. Some vines can even damage masonry. Most home inspectors evaluate vines on a case-by-case basis and pull them back in several areas to look for damage, particularly at the trim. Evidence of moisture damage to the building skin or mechanical damage caused by the vines themselves should be reported. You may recommend removal of the vines, but you should point out to clients that it may be difficult to remove all traces of the vines, especially from rough-textured stone, brick, or stucco.
1.3.6 Insulation Problems
CAUSE
Sometimes you will see a large number of patched holes on exterior wall surfaces. If these are in a uniform pattern (Figure 1.8), they often indicate insulation blown into the wall. This insulation can include cellulose and controversial materials such as urea formaldehyde foam insulation. Adding insulation through building exteriors is a retrofit to reduce energy costs and improve house comfort. This approach is usually taken when no interior renovations are planned but insulation improvements are considered a priority.
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Part I
F I G U R E
Exterior Cladding 1.8
Insulation Holes A uniform pattern of patched holes on exterior surfaces usually mean that some kind of insulation (e.g., cellulose, mineral wool, or urea formaldehyde) has been added The plugged holes may only be found in some walls or portions of walls
IMPLICATIONS
Leak Spots Insulation May Cause Damage
STRATEGY
Adding insulation from the outside creates a number of holes in the exterior siding that may not be well patched. In some cases, the patches are very visible. In other cases, they are patched so well that they are completely invisible. Poor patches may be water entry points. Insulation in old walls can reduce temperatures in wall assemblies and result in condensation problems where none had existed before. The insulation makes the wall cavity colder. Since insulation is often added without providing an air/vapor barrier, there’s a higher risk of the warm, moist air that leaks through the walls condensing within the wall system. Watch for patched holes that suggest insulation has been blown in. It’s often not done to the whole building, because it’s expensive. Watch for areas on the north or west sides of buildings, which are typically colder. Watch also for small areas that project out from the house, because they tend to be cool and uncomfortable. This includes second floors overhanging first floors, bay and oriel windows, etc. Check that the application holes have been patched and are weather-tight. Suspect concealed water damage to the walls caused by condensation, especially in cold climates. Watch for evidence of water damage, especially near the bottoms of wall assemblies. Again, you’ll have to check on the inside as well as the outside of the building.
Chapter 1
An Overview of Wall Surfaces
19
1.3.7 Summary Water kills houses. It’s a problem at roofs, at foundations, and on the exterior cladding. If you think about nothing else as you inspect the outside of homes, think about water getting into the building.
CHAPTER REVIEW QUESTIONS Instructions: Answer the following questions on a separate sheet of paper; then check your results against the answers provided in Appendix E. If you have trouble with a question, refer back to the chapter to review the relevant material. 1. List ten exterior wall surface materials that you’ll commonly find. 2. List six common components of an exterior wall assembly. 3. List three functions of building or sheathing paper. 4. Housewrap is used instead of ________. 5. What is used to secure brick veneer walls to wood frame houses? 6. List six common problems that are found on all wall systems. 7. What are the implications of a foundation wall that is below the exterior grade level? 8. What are the implications of burying weep holes on brick veneer walls?
KEY TERMS
cladding
air/vapor barriers
spalling
wall assemblies
sheathing
weep holes
structural members
building paper
veneer walls
interior finishes
housewrap
planters
insulation
siding
vines
