The first impression most people have of a home will come at the first glance of the home’s exterior. Cracked brick veneer, rotted doors and windows, and weather damage are just a few of the defects that detract from a home’s charm and beauty. Jade Home Inspection can determine the causes of all your home’s exterior defects and recommend cost-efficient solutions to the problems. Here are a few of the exterior issues we are acquainted with:
[learn_more caption=”Brick Veneer Issues”]
There’s no question that brick veneer is probably the most popular siding material used in median to upper scale residential construction in North Alabama. Therefore it’s no wonder that so many brick veneer problems pop up during residential home inspections.
Part I. Leaks in Brick Veneer
Contrary to popular opinion, brick veneer is not waterproof. In fact, it can leak during periods of heave rain, especially if the individual brick units are laid in weak (poor quality mortar mix) and sloppy (porous) mortar joints. The leakage occurs through cracks and separations and open gaps/holes in the mortar or through cracks in the brick not necessarily through the clay-fired brick masonry units, themselves. Thus, the use of a properly blended (high quality) mortar mix and full-head and bed (completely filled) mortar joints is mandatory for water tight brick veneer construction.
In spite of using quality mortar and full head/bed joints, water leaks may eventually occur due to cracking in the brick or mortar. In other words, very fine cracks will almost surely develop in any brick veneer due to a variety of causes, including normal weathering. These cracks are typically too small for us to see so we’re often oblivious to their presence. Because of this cracking tendency, the major building codes (throughout the country) all require the use of proper flashing details above windows/doors and at the base of walls, with proper water-proofing measures between the brick veneer and the wood-frame building structure. The latter is best accomplished by covering the wood-frame building with an air/moisture barrier (like Tyvek) then tucking plastic flashing beneath this barrier and out through the brick — through a single, horizontal, mortar joint which is usually located at the steel lintel supports above windows/dooors and somewhere just below the top of the foundation wall. The vertical joints between the brick, called head joints, directly above this tucked-in flashing, are left open at some close, uniform spacing, to allow the penetrating water to seep back outside the brick veneer wall. These open joints are called “weep holes”.
For more information about weep holes and the use of proper flashing details above windows/doors (at steel lintels) and at the base of the foundation, you can contact the Brick Industry Association at (703) 620-0010 and request a copy of their Technical Notes numbers 7, 7A – 7D & 7F; or visit their web site at www.bia.org and order on line. I’ve provided a direct link to the BIA on our web site (go to the links page).
Part II–Sagging Garage Door Steel Lintel Beams
Perhaps the most common brick veneer cracks in residential construction, other than those cracks associated with differential foundation settlements and brick expansion, are the ones that form above double-wide, garage door openings. This is my personal observation (based on more than 25 years of residential inspection experience) and may not be an accurate or factual statement. Nevertheless, it is my opinion/contention that crack formations in brick veneer above/beside double-wide garage door openings are the rule rather than the exception. I’ve seen hundreds of them!
In order to understand the causes of these cracks, one needs to understand the way in which brick veneer is constructed above such wide openings. In most cases, the brick veneer located directly above the opening is supported by a structural steel angle (beam) which in turn rests on the side wall sections of brick veneer (abutting each side of the door opening). These steel angles are commonly called “lintels or steel lintels” and generally have an outstanding leg which measures about 2-1/2 or 3-1/2 inches wide. Note that this width conforms to the typical brick masonry units which are used in residential construction; i.e. they range from 2-1/2 to 3-1/3 inches wide.
The general construction procedure is to lay-up the brick veneer, along each side of the garage door opening, until both sides reach the tops of the door jambs. At this point, the brick masons stop laying brick and the newly-laid brick veneer wall is allowed to harden or cure. After a day or two, a steel angle beam or “lintel” is laid across the top of the garage door opening the ends of the beam resting directly on the two brick veneer walls which directly abut the sides of the garage door frame. Once the lintel beam is in place, the masons continue laying the brick veneer, up and over the steel lintel, eventually embedding the lintel and hiding it from view.
The size (thickness and cross-sectional dimensions) of steel angle needed to span across the door opening and adequately support the brick above is based on the weight of the brick above the opening. In other words, the taller the brick veneer wall above the opening, the more the brick weight. For very tall heights of brick veneer, however, which exceed the height of an imaginary equilateral triangular who’s apex is created or formed by two sides oriented 45 degrees to the base (lintel), the total weight applied to the lintel is assumed to be the weight of the brick veneer located inside this triangle. The brick overlying and/or outside this triangle is assumed to arch or span across/over the opening. For a 16 foot wide opening, the apex of an equilateral triangle is 8 feet tall!
A normal rule of thumb for determining the weight of brick veneer is to assume that it weighs about 30 pounds per square foot of “face area”. Hence, a one foot wide strip of brick veneer wall, eight feet tall, weighs about 240 pounds. As such, an 8-foot tall brick veneer wall exerts 240 pounds per linear (lineal) foot on the supporting foundation/footing/lintel/etc. Fortunately, in most residential cases, the height of brick veneer above the garage door (steel lintel) is usually only about two to three feet tall. In these cases, the weight of brick supported by the lintel is equal to a uniform load of roughly 60 to 90 pounds per linear foot (30 psf x2 ft or 30psf x3ft).
In spite of this apparently small weight, however, I can tell you that there are no readily available steel angle sections (that a local builder can purchase from a steel fabricator) that can span 16 to 18 feet, support its own weight plus that of 2 to 3 feet of brick veneer, and not deflect, twist or bend excessively. And here is the rub. Excessive deflection is defined as the lesser of 0.3 inches or L/600 inches, where L is equal to the lintel span in inches. For a 16 foot lintel, L/600 is equal to 16×12/600 which equals 0.32 inches. That’s roughly 1/3 of an inch (between 1/4 and 3/8 of an inch). This rigid deflection limit has been set by the Brick Industry Association (BIA) — formerly the Brick Institute of America (refer to their Technical Note #31B). The Standard Building Code (which governs construction in Alabama) recognizes and references the recommendations of BIA. The purpose of the deflection limit is to improve/ensure the long term serviceability of brick. It is not to imply that whenever larger deflections occur in practice, there is some “implied” major structural problem or concern. The deflection limits simply reflect the fact that brick veneer is a hard, rigid and “brittle” material which cannot take (endure) very much distortion without cracking. Hence, to avoid cracking (which leads to more problems, such as leakage), the BIA has placed rigid deflection limits on any lintel beam used to support brick.
This means that whenever we see steel angles being used to span across wide openings, like double car (wide) garage doors, they are hopefully bolted or secured to some type of back-up structural member that helps provide the added strength (rigidity) necessary to prevent excessive deflection/twisting, and therefore brick veneer cracking. And this “hope” brings me back to the basis of this article….I contend that if one were to drive throughout North Alabama, and measure the deflections of the steel angle lintels being used to support the weight of brick veneer extending above double-wide garage door openings, the measured deflections will typically exceed 3/8 of an inch. I further contend that in those cases where the deflections are about 3/4 of an inch or larger, you’ll find brick veneer cracks somewhere above the lintel. Conversely, in those cases where the deflections are ½ of an inch or less, I bet you won’t find cracks at least cracks due to deflection.
If my predictions prove true, I hope you’ll admit that there is a serious problem in our local home building industry. In other words, excessive deflection would imply that the steel angle lintels are not being connected to or reinforced by structural back-up units/members. As such, there appears to be a serious “lack of knowledge” amongst the local home building trades (and obviously the Code enforcement agencies) regarding the limitations of steel angle lintel beams. Otherwise, there’s an ongoing blatant disregard for proper lintel beam installation in our local residential construction. Please discuss this topic with your builder friends. Encourage them to contact the Brick Industry Association at (703) 620-0010 and request a copy of Tech Note 31B. [/learn_more]
[learn_more caption=”Wood Rot”] If wood rot has occurred, it will require repair.
A common source of wood rot for floor structures is a damp, ventilated crawl space. Building Codes have long required that a crawl space should have foundation vents within three feet of each major building corner and every ten feet between these corners. An intact, plastic vapor barrier should cover the ground beneath the house. Water can seep under or through the foundation walls into the crawl space. So, adequate drainage around the outside of these walls is very important to keep the ground from becoming saturated. Another source of moisture can be an air conditioning condensate drainage pipe that incorrectly drains water into the crawl space. It should be made to drain outside the home.
Water in the crawl space can promote the growth of mold, mildew, and fungi that actually eats and weakens the wood of the floor substructure. Wood is a hygroscopic material so it readily absorbs water vapor. Wood absorbs water slowly, and it can take a considerable amount of time before dry wood can absorb enough moisture to be in danger of decay.
A particularly dangerous source of water in the crawl space is any kind of hot water leak. Steam seems to promote rapid bacterial and fungal growth.
Mold and mildew belong to a large botanical classification known as fungi. Mildew is a black fungus that grows on the surface of wood and darkens it over time. Although it doesn’t cause damage, it is a tale-tell sign of a high moisture condition. Mold and mildew often grow on surfaces when the relative humidity (RH) near the surface is above 50 per cent.
Decay organisms are also fungi, but they typically take longer to get started than mold or mildew. Decay fungi can attack wood and other materials when the moisture content(m.c.) is above 20 percent. The percentage of RH is different from the percentage of m.c. In most homes the m.c of the building material is considerably less then the RH of the air surrounding it. The m.c. of wood is expressed as a percentage of the wood’s oven-dried weight.
A living tree contains a certain amount of water. For example, the m.c. of a birch tree might be 75 percent. By the time the lumber from the tree reaches consumers the wood has usually dried to about 19 percent m.c (15 percent for kiln-dried products.) The wood in a home continues to lose moisture over time until it reaches equilibrium with the climate it is in; the m.c. of wood in most homes is typically less than 10 per cent.
Decay problems occur when wood remains wet for an extended period. For example, if there is a plumbing leak under a bathtub the floor can be wet for many months. Remember that wood absorbs moisture easily, but slowly. If there is enough moisture present for a long enough period of time, the m.c. of the wood can rise above 20 per cent and decay is a strong possibility. If a leak is temporary, the wood won’t be wet long enough for decay organisms to attack it.
The best way to cure a moist/humid crawl space is to close off the foundation vents, cover the ground surface with a seamless vapor barrier, attach the vapor barrier to the perimeter foundation walls and interior piers, then insulate the perimeter foundation walls and heat and cool the crawl space using the home’s central heating and cooling system. When this is not possible, you can place a specialty dehumidifier in the crawl space — one designed for this specific application, and be sure to direct the collected condensate outdoors. [/learn_more]
[learn_more caption=”Chimney Separation”]
A fireplace adds warmth to any home. Whether lying before a quiet romantic blaze or huddling near a roaring conflagration, humans have made fireplaces part of home designs since it was first figured out that being warm was better than being cold.
That fact hasn’t changed over the years. Neither has fireplace making. It still involves stacking blocks or bricks in a way that will allow fuel to be burned efficiently, heat to be conducted into the room, and smoke to be ushered up the chimney. And this is important, too: that stack of bricks, usually weighing ten or more tons for even a modest chimney, has to stand up straight.
So you’re out eyeballing the old home place. You admire the straight lines of your home. Lack of sag is usually a good thing. But something is amiss. You take a closer look. It’s your chimney! It’s…leaning! Get a grip. Calm down and feel the firm earth under your feet. Wait a minute! Maybe that’s the problem. How firm is the earth under your feet?
Leaning chimneys are usually caused by settlement or bearing soil failure. It doesn’t take much. For example, if the outer edge of your chimney’s footing sinks just 1/4 of an inch, the resulting crack between the chimney and the roof can be as much as two to three inches! Tiny slip at bottom equals huge gap at top. Through that gap can come all sorts of trouble. And that trouble is usually in the form of water.
The sandy silty clay soils often found in Alabama normally provide a firm foundation and usually stay put. It’s when the footing is placed on soil that has been “disturbed” during construction, or, worse yet, soil that has been contaminated by building debris or other foreign matter, that the problems often begin.
Even such susceptible soil, though, usually needs a reason to move. And that reason is usually in the form of water.
While you’re trying to figure out why your chimney is out of plumb, take a look at how water drains around your little piece of paradise. Is water moved away from your house? Do your gutters keep it away from the foundation of your chimney? Highly plastic clay soils can shrink or swell due to changing moisture conditions. Winter rains usually mean swollen soil. Summer soil is comparatively dry, or desiccated.
Such movement, as natural as it is, is detrimental to masonry structures and provides an opportunity for the chimney to rock back and forth and separate from the home. Usually this is nothing to worry about if the chimney footing bears deep into the ground.
Exaggerate this motion by poor drainage, however, and you’ve got a problem. Make sure water drains away from your house. Make sure that runoff from the roof does not saturate the ground around your foundation.
And before you exclaim that your chimney’s lean is due to nothing so mundane as water drainage (Thank you!), consider that the more exotic reasons, such as wind and lightning, rarely ever turn out to be the true cause. That is unless you’ve just come through a horrific storm. Even then, it was probably the copious rain and not the abundant breeze that made your chimney totter.
If lightening had struck your pile of bricks, there would likely be an explosive type of damage rather than an outward lean.
Wind? Probably not. If wind caused your chimney to lean, it would have to have been some fantastic and memorable wind, as in “You remember the wind of ’95. Put the part on a different side of my hair. Blew my chimney crooked, too.”
Not likely. Note that chimneys usually have only small areas subjected to the wind. Most of the structure is protected by the house and roof. The force of wind is usually negligible compared with the weight of the chimney.
So the gap between your chimney and your house continues to let water ravage your roof, your floor, your walls. You know water. And on top of that, your chimney might go ahead and fall on over. What can you do?
Call a professional. The inspectors at JADE Engineering will be happy to visit your less-than-perpendicular pile of bricks and tell you if the problem is worth fixing. A JADE engineer will even arrange a soil test to reveal just what kind of dirt you’re dealing with. If the underlying soil is an expansive clay or pile of rubble — as in former dump — then an appropriate repair can be developed.
Keep in mind, though, that trying to straighten a leaning chimney is not a do-it-yourself proposition. Your JADE engineer will be able to recommend people who are experts at this complicated and exacting task.
Here’s one way a professional might go about straightening your chimney. Vertical shafts are drilled several feet deep along the edge of the chimney’s foundation. These are then filled with reinforced concrete. The pour is stopped about 12 inches beneath the footing bottom and the concrete allowed to cure. The solid concrete pier can then become a surface for jacking the original chimney footing back to level. Once the footing is level, or plumb, then the remaining space between the original footing and the pier cap can be filled with concrete.
Once your chimney is level, you can then repair the displaced roof flashing. Remember: seeping water is never idle.
If the inspection reveals that your chimney is too far gone, then you can dismantle it and rebuild. This time make sure the footing is made competent by being big enough to spread the massive weight of the chimney over a large enough area. And make sure you have dug deep enough to reach undisturbed soil that will bear your chimney’s weight over the long haul. [/learn_more]
[learn_more caption=”Hail and Wind Damage”]
The effect of hailstone impact on roofing materials has been studied by several different authorities, including the U.S. Department of Commerce. Their findings, published in a paper entitled, “Hail Resistance of Roofing Products,” indicates that damage to shingle roofing should not be defined as cosmetic surface indentations. Only actual fractures in the surface coating or base material should be defined as damage. Superficial scuffing does not interfere with the performance of the roofing product. The Commerce Department’s tests further revealed that fiberglass-asphalt shingles, as opposed to the older organic-mat shingles, have excellent resistance to hailstone impact — at least for hailstone less than or equal to two inches in diameter. The reason is that the fiberglass mat provides greater tensile strength and toughness inside the shingle.
The amount of hail damage suffered by a roof depends on its age and on the type shingle used. The older and weaker organic felt-based shingles are known to undergo rapid natural deterioration from ultraviolet radiation exposure. The deterioration is usually manifested as cupping or curling of the individual shingle and/or extreme loss of granular surface material. When hailstones strike the surfaces of these older, brittle materials, they can actually break through the shingle. This leads to a rapid degeneration and material breakdown, increasing the chance for leakage.
Small indentations on shingles, therefore, are not considered damage, if the fiberglass base mat is not fractured. Breaks in the base mat will allow leaks, while surface dents and dings will not affect the shingle’s ability to repel water.
Hailstones with diameters of 1-1/2 inch or more are usually required to break shingles or knock holes in them.
Accompanying high winds can damage roofs by blowing off deteriorated or loose shingles, and cause other problems as well.
A common problem with assessing wind damage is that strong wind is often blamed for damage to a home that existed before the wind, but was never noticed until a storm or the close proximity of a tornado prompted scrutiny.
Besides knowing that a direct hit by a tornado will shatter and scatter almost any building, or that direct hits by tornado-launched debris can inflict much damage, most people know little about any other effect a tornado can have.
Research conducted by the University of Chicago, The National Weather Service, the Institute of Disaster Research, and others has established common rules about tornadoes and dismissed some of the myths, such as atmospheric over pressure damages to residential buildings, with the book most often cited being, Tornado: An Engineered Oriented Perspective. This book describes tornado damages as always increasing from the “outside in” and the “top down.” Residential buildings invariably suffer much worse exterior damages than interior damages and invariably these damages are also worse on the upper levels. The primary destructive components of a tornado are wind pressure and flying debris. Therefore, a tornado is likely to damage the roofing and exterior siding of a building prior to causing damage to the interior or foundation structure. Hence, unless exterior damages are significant, the likelihood of interior damages are very small.
Yet, many people insist that a passing tornado “twisted” their home, or lifted it off the foundation and set it back down, causing damage.
This discovered damage is often the result of years of poor maintenance, noticed only after a tornado has passed. [/learn_more]
[learn_more caption=”EIFS and Stucco Problems”]
EIFS (exterior insulation finish system), often called Dry-vit, coats a home or office building with a hard, rigid covering that can be applied to a flat surface of any shape. Available in hundreds of colors and several textures, EIFS is a versatile alternative to brick veneer or vinyl siding. Its use in construction allows an architect to employ design shapes and angles that would be impractical if stone, brick or other conventional siding were used. EIFS is also less expensive to install than many conventional exteriors. And, it can provide the most thermally efficient exterior wall covering available.
When properly installed, EIFS can provide an attractive protective shell for the building’s substrate, be it wood or metal. If manufacturer’s installation guidelines are not strictly followed, however, EIFS can develop cracks and leaks that allow water to get behind the textured facing and damage the substructure. Water intrusion behind the EIFS is its most common problem.
Proper installation is critical around doors and windows, with the EIFS stopped about 3/8-1/2 inch from the door or window frame and an expansion joint placed there. The joint should consist of a closed cell back-up rod and flexible sealant at least 3/4-inch deep.
Moisture intrusion can also take place where the EIFS intersects horizontal and vertical surfaces. According to the manufacturers, the EIFS system should be held no closer than two inches from the top surface of the roofing shingles. This prevents roof-shed moisture from contacting the bottom surface of the EIFS and rising up through it. At any point where the system terminates against a dissimilar material, such as siding or masonry, a minimum 3/4-inch gap must be left for an expansion joint and caulking.
The most common type of Exterior Insulation and Finish System (EIFS), sometimes referred to as synthetic stucco, typically consists of five components: adhesive, insulation board (attached to substrate with the adhesive), a base coat into which a fiberglass mesh is imbedded, and a decorative finish coat in the desired color. This type system, called a face sealed barrier EIFS, resists water penetration at its outer surface. It is not intended to drain water from behind, however, and in this way it differs from some other types of cladding that have a weather resistant barrier behind the cladding and may have air spaces between the cladding and substrate.
The base and finish coat known as the Lamina, is quite water-proof, so, once moisture intrudes behind the lamina, there is no where for it to go. Such water intrusion in wood-framed, EIFS-clad houses has become a major issue to EIFS makers, applicators, home builders, code officials, real estate agents, homeowners and home buyers.
The EIFS marketplace suffers from an abundance of inadequate and misleading information, according to the NAHB (National Association of Home Builders), which conducts EIFS Remediation Seminars to demonstrate when and how EIFS and substructure repairs should be made. One of the most common myths about EIFS is that any water intrusion requires complete removal of the cladding.
Good EIFS maintenance starts with regular visual inspections, preferably two per year. Even when properly installed, sealant areas require periodic inspection and maintenance. The effective life span of sealant varies greatly, depending on environmental conditions, sealant type and installation. It might be as short as three years under severe conditions. Under more typical conditions, the sealant might not need replaced until after 8-10 years. Check for missing, damaged, or deteriorated sealant between the EIFS cladding and windows, doors, and around electrical fixtures, electric meter bases, hose bibs, refrigerant lines and vents — any opening in the lamina.
Only polyurethane or silicone sealant meeting the ASTM C920 Standard Specification for Elastomeric Joint Sealant should be used. Any replacement sealant should be of the same type that was originally used. Polyurethane sealant, for example, should not be used to replace silicone sealant because polyurethane does not bond well to surfaces contaminated with silicone. However, silicone can be used to replace polyurethane, so silicone is a safe choice if you do not know which kind was originally used. Inspection of the lamina might reveal cracks, holes, and discoloration, requiring the services of a qualified EIFS installer or repairer. Staining might also occur, often from soil back-splash or from sprinkler over-spray or from mildew and mold. Proper installation of EIFS requires that it be terminated at least eight inches above grade. Avoid bare earth near the structure, and remove any vegetation that might prevent the lamina from drying after a rainstorm.
Stains and mildew are not usually associated with moisture intrusion and can be washed off. Consult the manufacturer of your system to get their specific cleaning recommendations. Dry-vit, for example, recommends a solution of 1 gallon of water, 1 quart of bleach and 1 cup of trisodium phosphate. Before you clean, make sure the surface is in good shape and there is no missing sealant (to avoid introducing moisture behind the cladding.) Since the finish coat of many EIF Systems is noncementitious, washing should be done as quickly as possible to avoid softening the finish coat. The finish coat can be damaged by harsh chemicals, strong cleaners, many solvents and extremely hot water. A mild liquid detergent is typically safe to use with a soft-bristled brush. Do not use wire brushes or other abrasive tools.
Damage can be significant if moisture intrusion goes undetected. Inspection of an EIFS-clad building by an engineer or other qualified professional should be routine. The location of water entry is often difficult to see, and any damage to the substrate and structural members behind the exterior often cannot be detected by visual inspection. Inspections should be done annually, using both a non-invasive moisture meter and a probe-type meter that penetrates the lamina. Such meters are usually the only way to detect moisture behind the lamina.
For more information concerning EIFS damage and repair, contact the NAHB Research Center’s HomeBase Hotline, at 800-898-2842, or their website at www.nahbrc.org.
Remember that even EIFS installed scrupulously, following manufacturer’s guidelines, can develop problems. Conversely, EIFS that was not installed to the letter of the guidelines can, with proper maintenance, provide satisfactory service. [/learn_more]
[learn_more caption=”Roof Support Problems”]
There are two primary roof framing systems used by local home-builders: rafters and trusses, as well as two primary roof shapes: gables and hips.
Rafter-framed roofs consist of individual rafters (sawn lumber members), usually spaced from 12 to 24 inches on center, which span from the exterior walls or roof-eaves up to the roof top or ridge, or into the sides of the main hip rafters. This style of roof construction is often called “stick-framing”. The most common rafter size is a 2×6; unfortunately, this small-size member cannot span very far and must typically be braced near mid-span. A structural analysis will usually show that the roof-bracing system picks up most of the roof load (weight). Hence, it is very important that the roof braces land (rest) on only designated interior “load-bearing” walls. Unfortunately, it appears as though many builders/framers do not realize this since they often support the roof bracing systems on the closest or most convenient interior room partition wall. This can lead to long-term floor sag because most floor joists are not sized for roof loads.
The ridge board located along the peak of the roof typically does not provide any structural support for a rafter-framed roof system; it simply serves as a convenient bearing-plate or nailing plate for the opposing rafters. However, it is important (and a Code requirement) that the ridge board be deep (tall) enough to provide full contact to the cut face of the mating rafter and that opposing rafters meeting at the ridge directly align with one another. Whenever the ridge board is non-structural, it is absolutely necessary that the roof rafters be lapped alongside and connected to the underlying ceiling joists at the exterior wall plate; moreover, the ceiling joists that extend across the home must be properly lapped and connected to one another because they provide a critical “tension-tie” across the home. If the ceiling joists do not provide this critical tie or if they span transverse to the roof rafters (which is often the case), the roof ridge will likely sag and the exterior walls will likely lean outward.
The latter is a common problem with stick-framed cathedral roofs/ceilings. In this type of roof system, the rafters and roof decking also serve as the interior ceiling. Since a conventional rafter-framed roof exerts outward forces on the supporting exterior walls, a structural ridge beam (board) is required for cathedral ceiling construction because there are no ceiling joists to provide the normal cross-tie. In other words, if the ridge beam is capable of providing vertical support to the rafters, then they do not exert an outward thrust on the supporting exterior walls. A structural ridge beam normally consists of either glue-laminated timber (glu-lam), laminated veneer lumber (LVL) or structural steel. Seldom will a solid-sawn lumber beam or built-up lumber beam suffice-especially for long ridge beam spans.
Failure to provide a structural ridge beam in cathedral ceiling construction always results in roof sag and corresponding outward lean in the exterior walls which support the rafters. Although I have never witnessed the collapse of an improperly constructed cathedral ceiling, I suspect that it can happen. The reason why complete failures don’t occur is probably because the distortions that slowly develop inside the home, from leaning walls and sagging roofs, gives the homeowner plenty of time to hire a professional to develop a corrective repair. Hence, this condition should never be ignored, no matter how slight the distortions.
Truss-framed roofs consist of pre-engineered, light-gage-metal-plate-connected sawn lumber members which are fabricated inside a controlled environment, per some proprietary engineering design and delivered to a construction site on flat bed trucks or special “cradle trailers.” These structural units/frames are designed to withstand numerous Code-specified structural load combinations and, because of their engineering and close fabrication tolerances, often provide the best solution to complex roof shapes or difficult roof framing configurations. Trusses usually transfer all of their load to the outer bearing points (exterior walls); because of this, they do not need any support from interior room partition walls. Because roof trusses are designed to span across the entire width of a home, the top chord of the truss and oftentimes many of the interior web members are placed into compression. The compressive forces try to make the truss members buckle or distort out of plane and, unless they are properly braced and held straight during erection, the entire truss may warp and distort. This can lead to reduced load-capacity, increased deflection, and the possible transfer of roof load to interior room partition walls. Once the roof decking is nailed to the truss assembly, the top chords become permanently braced. The very long compression web members (interior diagonal members between the top and bottom chords) still require some sort of permanent bracing to prevent them from distorting. Many home builders and framers do not realize this. Another problem with trusses is that very long/large trusses are usually flimsy and somewhat fragile and hard to handle at the job site. Unless the trusses are handled and stored very carefully in the field, and later during actual erection, the metal-plate connections may detach from the wood members. If this occurs, the truss has been compromised and will no longer behave as designed unless repaired properly/immediately. Also, if any truss member(s) are cut or damaged during construction or later by other trades (electricians, plumbers, HVAC), the truss will be compromised and rendered somewhat ineffective. In either case, the end result is usually roof distortion, ceiling distortion or the creation of isolated floor sag. [/learn_more]