Preventing Roof Damage from Rusted Fasteners

These days, the majority of metal roofs are made from Galvalume coated steel, which typically carry a warranty against perforation due to rusting for a period of 20 years. A study on Galvalume standing seam roofs (SSR) conducted at the behest of the Metal Construction Association (MCA) showed that a properly installed Galvalume SSR can be expected to last 60 years or more.  However, the caveat is “properly installed”. One of the major issues that will drastically reduce the service life of a Galvalume-coated roof is the use of non-long-life fasteners in exposed locations.

Anytime you have an exposed fastener on a metal roof, you risk rust—the term commonly used for the corrosion and oxidation of iron and its alloys. While a little rust might not seem like a big deal, its presence can actually be a harbinger of severe damage to your metal roof panels if not caught early, or ideally, stopped before it ever has a chance to start.

The issue is most prevalent on R-panel roofs due to the use of exposed fasteners. And even with standing seam roofs, which use clips and are typically referred to as a concealed fastener roofs, there are exposed fasteners as well, most often at the eave, the end laps and at trim, such as ridge flash, rake trim, and high-eave trim.

Prevention

The best recommendation for any exposed fasteners (meaning they are exposed to the weather and other harmful elements), is that they should be long-life fasteners. When you don’t use long-life fasteners, they start rusting with exposure to moisture and, over time, the rust virus stretches down to the roof, causing severe and often irreparable damage.

Suppose you have a metal roof that is 10 to 15 years old. Depending on the environment, the roof could be in excellent shape—except for where those screws are; you can have holes right through the roof at the fastener locations. More people than ever are starting to realize they’re supposed to use a long-life fastener, in a case like this. We see a lot of roofs when we inspect them for weathertightness warranties. What often happens is a worker on the roof may have just grabbed some screws that were handy without thinking about the kind of screw or the inevitable chemistry that could potentially cause rusting. Or, you may have a situation where there is some type of accessory put on the roof by another trade, perhaps a plumber or an HVAC installer—and maybe they didn’t use long-life fasteners.

The best recommendation to mitigate this potential problem is two-fold. First, make sure roofing installers know to use a long-life fastener at every exposed location. Secondly, make sure that every other contractor working on the roof that you’re responsible for knows to use long-life fasteners with whatever they’re doing.

 

Fasteners
A long-life fastener (left) can withstand the elements and prevent rust buildup longer than other fasteners. A regular fastener (right) will begin to rust upon exposure to moisture.

What if rust does occur?

One question frequently asked is: if the fasteners do become rusty, do you have to replace all the panels? If you catch the problem before the rust virus makes its way down to the roof itself, you can just change out the screws. However, if the rust has compromised the roof, you very likely would have to change out all the panels, at the least everything that has been affected—just because of one little spot. Truthfully, if the rust is in one spot, it’s probably all over.

Another thing worth mentioning is if aluminum panels are used along with typical long-life fasteners, it could still rust, especially if the roof is exposed to salt spray (think close to the coast).  The answer in this case is to use a stainless steel screw, which are long-life fasteners (but not all long-life fasteners are stainless steel).

Be aware from the start.

It’s crucial for installers and contractors to take notice and order the right fasteners from the start so that problems can be avoided.

Also, after some wear and tear, if subsequent work is done on the roof, everyone involved should take note. For instance, you buy a building and somewhere down the road you decide to frame out a small office and add a bathroom. You’d need a water heater, so a plumber goes on the roof, puts in pipe penetration and doesn’t use long-life fasteners. The onus would be on the owner to ensure that everyone performing work on that roof—no matter when—is using long-life fasteners.

Conclusion

The best-case scenario with a metal roof is to get the right fasteners to begin with. However, if the roof is already installed, the next step is to be on the lookout for rust and if you notice it, consider that it might be because of the fastener.

If that’s the case and you catch it early—when it’s just the screws that are rusting but the rust virus hasn’t yet transferred down onto the roof, you can just change out the screws with the proper long-life fasteners. We recommend doing a roof inspection at least once a year. If you see any loose or rusty screws, replace as needed.

For more information on MBCI’s broad selection of metal roof and wall panels, contact your local MBCI representative.

Standard Testing for Metal Roofing – Part 1: Structural Performance and Uplift Resistance

When selecting a metal roofing product, there is an expectation that it will perform as intended over the life of the building. But what assures building owners, code officials, or design professionals that a product will in fact perform as promised? This question often comes up in building product discussions and the accepted way to answer it is to subject the products to physical testing. The type of testing is usually very specific to the product based on protocols and procedures developed by independent agencies such as Underwriters Laboratories (UL), ASTM International, or others. Manufacturers typically submit their products to independent testing labs who follow these standard test procedures. Once testing has concluded, they report the results back to the manufacturer. These results then show whether the product meets stated performance criteria or not. If not, the manufacturer can re-design and re-test until it does and then make the final results available to the public.

For metal roofing, a series of relevant and important tests are typically performed. In this blog, we will look at two of them related to structural performance and wind uplift.

ASTM E1592

The structural integrity of metal roofing is crucial given the various natural forces that can be imposed on the materials. Effects from wind, snow, or other conditions can compromise its integrity. Accordingly, the ASTM Committee E06 on Performance of Buildings (including sub-committee E06.57 on Performance of Metal Roof Systems) has developed ASTM E1592 “Standard Test Method for Structural Performance of Sheet Metal Roof and Siding Systems by Uniform Static Air Pressure Difference”. While the standard acknowledges the use of computation (i.e. calculations) to determine the basic structural capacity of most metal products, it also points out that some conditions are outside of the scope of computational analysis and hence need to be tested.

The standard describes a test method with “optional apparatus and procedures for use in evaluating the structural performance of a given (metal) system for a range of support spacings or for confirming the structural performance of a specific installation”. As such, it is very specific both to metal roofing and its installation. This test method uses imposed air pressure not to look at air leakage but simply to determine structural reactions. It consists of three steps:

1. Sealing the test specimen into or against one face of a test chamber

2. Supplying air to, or exhausting air from, the chamber at the rate required to maintain the test pressure difference across the specimen

3. Observing, measuring, and recording the deflection, deformations, and nature of any failures of principal or critical elements of the panel profile or members of the anchor system

The test needs to be performed with enough variation to produce a load deformation curve of the metal and account for typical edge restraint (fastening) representative of field conditions.

Manufacturers need to submit different products that are tested at least once at two different span lengths between supports. Standing seam roof panels are typically tested at a 5’-0” and 1’-0” span. Spans between the two tested spans can be interpolated. The result is a table of tested loading results that can be compared to code required or engineered design loading to then determine if the selected material and spacing are adequate for the project needs or if another product or spacing is needed.

MBCI's metal roofing products undergo a series of tests to ensure maximum resistance and performance.
MBCI’s metal roofing products undergo a series of tests to ensure maximum resistance and performance.

UL 580

The ASTM E1592 test is focused on the structural integrity of metal panels. It also uses positive and negative air pressure in a static (i.e. non-moving) condition to determine performance. There is also a separate concern about how metal roofing will perform in a dynamic condition as would be expected in a windy condition where wind gusts can ebb and flow erratically. In that regard, a separate test developed jointly between Underwriters Laboratories (UL) and the American National Standards Institute (ANSI) looks at the ability of roofing to resist being blown off a building due to wind. Known as ANSI/UL 580 “Standard for Tests for Uplift Resistance of Roof Assemblies”, it has become the recognized means to identify and classify the suitability of roofing for different wind conditions – low to high.

This test is also specific in its scope and intent stating that it “evaluates the roof deck, its attachment to supports, and roof covering materials”. It also points out that it is not intended to test special roof conditions, main or secondary structural supports, or deterioration of roofing. The standard prescribes in considerable detail the type of test chamber that needs to be constructed and used for the testing which includes three sections: “a top section to create a uniform vacuum, a center section in which the roof assembly (i.e. deck, attachment, and roofing) is constructed, and a bottom section to create uniform positive pressure”. The test procedure is then based on placing the roof assembly into the test chamber and subjecting it to a prescribed sequence of 5 phases of oscillating positive and negative pressure cycles (simulating dynamic wind conditions) over 80 minutes of total testing.

There are four wind uplift classifications obtainable for a tested assembly based on the test assembly retaining its attachment, integrity and without any permanent damage. These include Class 15, Class 30, Class 60, and Class 90. Each class has its own requirements for test pressures with increasing pressure as the class number increases. Higher class numbers indicate increasing levels of wind uplift resistance. Note, that to obtain a Class 60 rating, the tested assembly must pass the Class 30 test then be immediately subjected to the Class 60 test sequence. Similarly, to obtain a Class 90 rating, the tested assembly must first pass both the Class 30 and 60 tests. Metal roofing manufacturers who want their roofing products tested and classified under UL 580 must pair them with standard roof deck and fastening materials. Hence most have many different tests performed and results reported accordingly.

When reviewing metal roofing options, it is comforting to know that most manufacturers have tested their products and designed them to meet or exceed minimum requirements. To find out more about tested results of products you may be considering, contact your local MBCI representative or see the MBCI website and select the “testing” tab under a selected product.

Knowing When to Call the Metal Manufacturer: Part 2

As stated in Part 1 of this series, the success of a metal roof or metal wall project can rest on the installer knowing when something isn’t working or just doesn’t seem right. When that happens, a call to the manufacturer is not just suggested but is really imperative to ensure any potential problem is averted before it’s too late. In addition to the previously discussed scenarios, such as damage to the physical panel or problems with the fasteners, let’s take a closer look at a few other common circumstances under which MBCI recommends immediately reaching out to the manufacturer:

Alignment and Substrate Issues

It is the installer’s responsibility to verify the substrate and check for proper alignment before attaching any sheeting materials. If the installer notices any issues of this sort (either before installation or once they start putting on the sheeting), they should stop and address them immediately. This might include oil canning or other irregularity in the appearance of the panel. The installer should investigate the source. If unable to identify and properly remedy the situation on their own, then a call to the manufacturer’s support team is recommended. They may be able to suggest items to check to help locate the source of the problem—whether it be installation or manufacturing—and from there make suggestions as to the best possible means to address the situation.

Accessories

When physically getting ready to modify a panel system by adding things to the roof (such as snow guards or mechanical curbs) or to walls by installing doors, windows and louvers, these penetrations can have an impact on the system and its weather-tightness and appearance. Oftentimes, other trades—who may or may not have knowledge of the sheeting system—are coming onto the job to perform the accessory installation. It’s wise to visit with manufacturer prior to installation and/or alert the non-metal panel installer of precautions to take when adding accessories.

bad roof jack installation - part #2 ACCESSORIES SECTION
The pipe penetration shown here is not the correct type of piping for metal roofing, and not the correct installation. This can lead to issues with roof performance, including leaking and water damage.

Coordination regarding material types of accessories, fasteners and placement is critical. There are materials that can react negatively with the installed system and lead to damage as well as void manufacturers warranties. Accessories should always be discussed prior to installation. Read more about different types of roof accessories and penetrations in MBCI’s blog article, Roof Penetrations Made By Non-Roofing Contractors.

Panel Engagement

Panel systems have an engineered means by which the panels attach and engage one another as shown in the manufacturer’s installation manuals and project drawings. If at any point the panel will not engage as depicted in the details, installation should be halted and reviewed to determine the cause. This can require a call to the manufacturer to help determine if the matter is site and substrate related or potentially a manufacturing issue.

Do not continue to install the system if the laps are not nesting properly, clips are not engaging as detailed, panel modularity cannot be controlled or if the overall panel is not “resting” on the substrate such that there is excessive bowing and stress in the panel. This is the time to call the manufacturer, as once the material is completely installed, it is much more difficult to determine the cause of a problem and is potentially more expensive to remedy. Additionally, in many cases, full installation constitutes acceptance of the product and the manufacturer’s hands could be tied or extremely limited in being able to assist in remedying after the fact.

By knowing when to be proactive with a call to the manufacturer, installers can mitigate many types of potential pitfalls. And if you’re just not sure, it’s best to call.

For more information on metal roof and wall products and training, MBCI offers courses through its Metal Institute. These courses are available for general training purposes or for those seeking installer certification.

Selecting Metal Panels Based on Roof Slope

If you’re reading this article, then you are probably already aware that metal roofing can provide many benefits, including longevity, durability and water shedding—not to mention the aesthetic features of today’s metal roof products. When specifying a metal roof system, choosing the correct panel is a key factor. Roof slope is critical in determining that choice. Let’s take a look at some of the main things to consider when choosing a metal roof panel with regard to roof slope, including building codes, minimum slope requirements and typical applications.

Building Codes

Building codes are perhaps the most important driving force dictating the roof slope to choose. Different types of roofs have distinct specifications for installation. According to the 2012 International Building Code (1507.4.2 Deck slope), minimum slopes for roof panels need to comply with the following:

  1. The minimum slope for lapped, non-soldered seam metal roofs without applied lap sealant shall be three units vertical in 12 units horizontal (25-percent slope).
  2. The minimum slope for lapped, non-soldered seam metal roofs with applied lap sealant shall be one-half unit vertical in 12 units horizontal (4-percent slope). Lap sealants shall be applied in accordance with the approved manufacturer’s installation instructions.
  3. The minimum slope for standing seam of roof systems shall be one-quarter unit vertical in 12 units horizontal (2-percent slope).

Minimum Roof Slope Requirements

Depending on the roof profile, there are minimum roof slope requirements for each panel, which need to be considered. The profile refers to the shape the metal sheets take when they bend to form panels. Metal roof slope is expressed by a ratio indicating the roof pitch, which notes the vertical rise of the roof (in inches) for every 12 inches the roof runs horizontally—in other words, dividing the vertical rise and its horizontal span. The most common slopes are: 3:12, 1/2:12 and 1/4:12. When looking at metal roofing panel, you will need to consult with the manufacturer to ensure that the metal panel you selected will work for your application.

MBCI Roof Panels and Minimum Slopes

Applications: Low Slope or Steep Slope

Commercial Application– Low Slope Roofs

A low-slope roof is one whose slope is less than 3:12. Low slope roofs have several benefits. They have simpler geometry that is often much less expensive to construct and low slope metal roofs require fewer materials than a steep slope, which reduce material costs. Metal roofing panels are excellent solutions for roofs with low slopes. Commercial roofs are typically low slope (less than a 3:12 slope), and larger than residential roofs. This is due to low slope metal roofs being a bit easier to build on large structures.

1/2:12 Metal Roof Slope
Cecilia Junior High in Cecilia, Louisiana uses 7,180 sq. ft. of MBCI’s SuperLok®. This panel requires a minimum slope of 1/2:12.
Residential Application– Steep Slope Roofs

A steep slope roof is one whose slope is greater than 3:12. Steeper slopes are ideal for areas that have higher snow loads and will also prevent the possibility of ponding water on the roof. When it comes to residential construction, your roof is a visible part of the structure. Choosing a metal roof for residential construction involves choosing a panel profile that will be aesthetically pleasing.

Steel Slope Metal Roof
It is common to use steep slopes in residential applications, such as this home in Guntersville, Alabama that utilizes MBCI’s LokSeam® (requiring a minimum slope of 3:12).

Conclusion

Regardless of whether you’re choosing metal panels for a commercial or residential structure, slope matters. Following common standards, doing your research and paying attention to manufacturer guidelines regarding minimum slope will ensure you’re reaping the full benefit of your metal panel selection.

For More Information

To learn more about metal roof slopes, check out:

Fastener Compatibility with Metal Roof and Wall Panels

The installation of a new metal roof or wall panel on a residential home, business or commercial building takes care, precision and—of course—the right tools. Regardless of the structure, you’ll likely find that choosing the correct mechanical fastener plays a key role in the long-term performance, durability and efficacy of the project.

Many metal roof and wall panels, in fact, rely upon the use of quality mechanical fasteners to secure components to a structure. In order to guarantee a resilient and weather-tight attachment, it behooves the user to select an appropriately compatible fastener type for the specific metal construction, thereby ensuring expected benefits, such as energy efficiency, extended life cycle, and even lowering insurance bills for the owner. In other words, once the decision has been made to use metal building materials for your roof or wall project, the next step is figuring out how to hold it all together.

Know Your Fastener Options

Before selecting fasteners for the project, it is important for the designer or installer to understand the various materials and options available. Typically, this involves the following considerations:

  • What type of material and coating is appropriate?
  • What type of head do I need? Does it need to be painted?
  • Do I need a washer? If so, what material should I use?
  • Should I use self-tapping or self-drilling screws?
  • What thread count should I specify?
  • How long does the fastener need to be?
Many Types of Fasteners
The MCA provides a summary of the different types of fasteners in their technical bulletin, Fastener Compatibility with Profiled Metal Roof and Wall Panels.

Select a Fastener on the Basis of Material

Most fasteners are made from coated metal but both the type of metal and coating must be chosen on the basis of the materials the fastener is bringing together. Galvanic action between dissimilar metals can cause premature fastener failure and lead to leakage. Even stainless steel screws will corrode severely under the right (or actually wrong) conditions. In extreme exposure, sometimes the best option is to use galvanized screws and plan on replacing them at a later date with a larger screw once the zinc has been depleted.

Considerations for Self-Drilling Screws

Self-drilling screws have a drill bit built in and don’t require a pre-drilled hole. Although self-drillers save the installer the step of drilling a hole, they are not always a good idea. The available space between the back of the hole and the next physical restriction must be at least as big as the bit itself or the threads will not engage. Also, drilling a hole allows a quick inspection to ensure the hole is in the correct location and plies are aligned and parallel. Generally, self-drillers are used when going through thin gauge steel into thicker gauge steel and self-tappers are used when fastening two thin gauge plies.

Washers

Fasteners may be used with or without washers. While plastic washers help prevent leaks, they are not required on purely structural connections. When using washers, it is important to visually inspect the screw after installation to be sure they are properly compressed and not kinked. Exposed plastics generally degrade when exposed to ultraviolet light. Furthermore, use of neoprene washers may be prevented by restricted material lists, or “red lists.” Fastener heads themselves may be made of different materials than the rest of the screw, long-life ZAC heads being the most common example.

Fastener Profiles

Fasteners have different profiles. Flat or “pancake” screws are used when low profile installation is necessary and may have Philips, hex, or Torx sockets. Which socket to use is usually an installer’s preference based on accessibility restrictions. Another common feature is an over-sized dome beneath the head to encompass a larger washer. Also called shoulder screws, these screws are useful when thermal movement might distort the holes.

Colored Fasteners for Metal Roofs
Fasteners can also be colored to match the roof or wall panel.

Thread Count per Inch

Thread count per inch, or TPI, must also be considered. Most commonly, fasteners are installed through the thinner ply first and grip in the thicker ply, pulling the plies together. Therefore, TPI selection is usually driven by the thickness of the thicker ply. Generally, the TPI is close to the gauge of the metal for gauge steel and higher for plate and sheet.

Length

The fastener must also be long enough to fully engage all plies of material, plus the length of the drill bit in the case of self-drillers. Generally, this is rounded up to the next half or quarter inch. However, the longer the screw, the more torsional strain is produced during driving and in the case of very long fasteners, this can break the fastener or introduce wobble, leading to poor installation. Therefore, stainless steel with over-sized washers is often used for long screws for added strength and protection.

For More Information on Fastener Compatibility

To learn more about fasteners and their compatibility with different types of metal roof or wall panels, check out Metal Construction Association’s recently published technical bulletin, Fastener Compatibility with Profiled Metal Roof and Wall Panels.

Design and Color Trends in New Metal Construction

Design and color trends in metal roofing products are not exactly black and white. In fact, a whole host of options are available when choosing textures and colors for new metal construction projects, depending on specific criteria. Some are practical, some are aesthetic—but all are shaping how designers are specifying metal products, coatings and paints. Let’s walk through a few of the top trends in the industry now.

More color options for coil coatings

Bright Color Options in Coil for Design
Through vertical integration, manufacturers are offering more color options than ever.

It used to be that coil options were limited to standard stock choices and availability was determined by the coil coaters. Now, with evolving industry strategies, such as NCI’s vertical integration, many more manufacturers are properly positioned to enter into the market with multiple color choices across multiple brands without as much deviation. This also allows manufacturers to quickly adapt to requests for custom colors—both internally or externally.

Ratings and regulations are leading to more energy-efficient choices

Moreover, color requests based on aesthetics and paint systems have evolved based on changing code requirements. For additional benefits, specifiers can turn to many rating systems, such as the Cool Roof Rating Council and ENERGY STAR®, as well as earn LEED points by having specific SRI (Solar Reflectance Index) values.

Much has changed over the past 10 to 15 years. For instance, the components industry has evolved from customers merely selecting colors based on preference to a more integrated approach accounting for aesthetics, cost and energy efficiency. Today, owners and architects are more likely to consider a color such as Solar White to save on insurance or receive tax rebates. Environmental considerations and regulations have changed the way customers purchase steel, incorporating such issues as unique regulations for different states and weather conditions, LEED points and reflectivity into the atmosphere.

Insulated metal panels used in higher-end architectural projects

Another design trend in the industry is a move towards insulated panels, mimicking what is typical in the aluminum composite material (ACM) world. High-end car dealerships are known for design with ACM. This includes blocked-off designs that can be elongated, can be different colors or have joints in different places. This application has been ACM’s primary wheelhouse for decades. Now that ACM manufacturers have entered into the insulated metal panel (IMP)  industry, more of the design community is considering a thinner, horizontal IMP. The intention is to replicate the appearance of an ACM panel, while reaping the major cost and insulating benefits of IMPs.

Depth of color and texture: the rise of metallic colors

Architecturally, more metallic paints are being used. Historically, metal panels were white, tan or Galvalume. The current trend has expanded to a wider color palette, including mica fluoropolymer. These metallic coatings give depth to the color, adding sheen and sparkle. In fact, there are actually metal flecks in the paint. Metal oxide-coated mica pigments offer up the metallic look and add to the durability.

 Signature® 300 Silver Metallic Color Design
Vasa Fitness in Lehi, Utah features MBCI’s FW-120 panel in Signature® 300 Silver Metallic paint.

What’s behind this trend? Designers are thinking about metal roofs in a whole new way. They are looking to leverage colors and properties of paint to bring out a unique architectural appearance not previously available.

Conclusion

Trends in metal construction are as broad as the choices of color and coatings. Whether a reaction to energy savings criteria or simply a desire of an educated consumer to bring new life to their project, it’s worth taking the time to investigate all your options when specifying your next metal project.

Better Barriers: Meeting Thermal Performance and Controlling Air & Moisture

Panelized metal exteriors have joints. It’s just a rule of best-practice design. Yet these joints are seen by some as interruptions in the façade or roof, when in fact they are connections — the opposite, one can argue, of the word “interruption” that suggests a discontinuity.

Edie's CrossingIn fact, engineered metal panel systems offer arguably the best possible continuous exterior system. Not only are they properly applied exterior to the building structure—outboard of columns, joists and girts—but they are also designed to ensure an unbroken chain of thermal control and barrier protection. Combined with controlled penetration assemblies as well as windows, doors and skylights that are engineered as part of the façade and roof system, the insulated metal panel (IMP) products provide unequaled performance.

That’s the main reason that specialized facilities designed for maximum environmental barrier control are made of IMPs: refrigerated warehouses, R&D laboratories, air traffic control towers and MRI clinics, to name a few.

But any facility should benefit from the best performance possible with metal roofing and wall panels. Consider insulation shorthand for the code-mandated thermal barrier required for opaque wall areas in ASHRAE 90.1 and the International Energy Conservation Code (IECC). For a given climate zone, says Robert A. Zabcik, P.E., director of R&D with NCI Group, the project team can calculate the functional amount of insulation needed by using either the “Minimum Rated R-values” method or the “Maximum U-factor Assembly” calculation. For IMPs, teams use the Maximum U-factor Assembly, which can be tested using ASTM C1363.

With IMPs, the test shows thermal performance values up to R-8.515 and better per inch of panel thickness, meaning that a 2.5-inch-deep panel would easily meet the IECC and ASHRAE minimums.

With metal roofing panels and wall panels, a building team can achieve needed energy performance levels with this single-source enclosure, providing a continuous blanket of protection.

The same is true for air and moisture control. In a July 2015 paper by Building Science Corp., principal John Straube wrote, “Insulated metal panels can provide an exceptionally rigid, strong and air impermeable component of an air barrier system.” He noted that, “Air leakage condensation cannot occur within the body of the insulated metal panel, even if one of the metal skins is breached, because all materials are completely air impermeable and there are no voids to allow air flow.”

In terms of water control, Straube writes that IMPs have a continuous steel face that is a “high-performance, durable water control layer: water simply will not leak through steel, and cracks and holes will not form over time. The exterior location of the water barrier,” he adds, “offers some real advantages.”

Clip-Fastener-AssemblyEnfold_blog

Connecting the panels at transitions, penetrations and panel joints is the key, of course. Straube notes that sealant, sheet metal, and sheet membranes are effective and commonly used to protect joints.

In my experience, these joint details are incredibly effective. They often outlast most other components of the building. Even more important, they help make IMPs better barriers that meet thermal, air and moisture performance needs. They help make metal panels one of the best choices of all.

Design to Your Client’s Mindset

Spring Fire Department Station 78

As an architect, when did you last hear your client say, “Money is no object?”  This happens … almost never!  More likely what you hear is “I want high quality for low cost.”  The challenge of the architect is to provide your client with high quality at a reasonable and appropriate price.  A large part of finding that balance is determining the values, goals and long-term perspective of your client.

If a building owner wants a metal roof, it’s likely they already have a reason why.  Perhaps their existing roof didn’t provide the service life they expected it to, or it was damaged disproportionately.  Or the building owner understands that a metal roof can last a really long time.  Or they like the look of a metal panel or metal shingle roof, with all the colors and shapes available.  As an architect, it is important to determine your client’s mindset.  In the end, the question comes down to, “How long will you own this building (or home)?”  And, although less common, a building owner may just want to build a high-end, long-lasting building no matter their desired length of ownership.

The large part of the cost of a metal roof, similar to other roof types, is the labor to remove the existing roof and install the new one.   Upgrading from a 24-gauge metal to 22-gauge metal is a minimal increase in material costs that is easily justifiable for the long term.  Metal thickness, coating type and thickness, and penetration and edge details are the areas where upgrades and enhancements occur.

Argue against value engineering.  Roofs certainly can be out of sight, out of mind to most owners, but building owners who are considering metal roof systems understand the concept of life-cycle analysis, whether they know it or not.  Overtly reinforce their long-term outlook to help ensure that high-end penetration details and edge details are designed and installed.  Look to the industry standards—SMACNA, NRCA—for details that will last the life of the metal panels.  Realize that metal panels don’t leak; joinery and flashings are the potential leak locations.  Upgrade the details to be of the highest quality.

Understanding the mindset of your client is critical to determining the level of design.  This is definitely a cost issue.  The “university” client thinks long term; the “developer” client thinks short term.  However, there is much middle ground that requires inquisitive discussion with an owner to determine his/her goals.  Ask the questions, and design a metal roof based on your client’s mindset.

Best Applications for Water Shedding Standing Seam Metal Roof Panels

A standing seam roof system, or SSRS, has exposed fasteners only at the eave and at specially designed end laps. The concealed clips installed at the panel seam typically allow the panel to float during thermal movement. These systems are normally manufactured in 24 gauge, though 22 gauge is often used.

People tend to classify SSRS as either structural or architectural, but those two distinctions aren’t absolute. There are many architectural SSRS that are structural systems, and most structural SSRS can be used in an architectural application. I think the better distinction is that SSRS are either water shedding or water barrier systems.

Water Shedding SSRSs

Water shedding panel systems are architectural SSRS, meaning they rely on gravity to shed water from the roof before it can build up on the metal panels. The steeper the roof slope, the faster the water will run off. However, in certain instances, these roofs still may allow water to infiltrate.

The following precautions can be taken to avoid this:

  1. Water shedding panel systems must be installed on a minimum roof pitch of 3:12 or greater. Panel manufacturers typically advertise the minimum recommended slope for each of their products.
  1. They must be installed over a solid deck, since they are not structural panels.
  1. The deck must be covered with a moisture barrier or membrane. This is critical as the moisture barrier is the last line of defense once water gets under the metal roof panels. The industry standard for years has been #30 felt. I think this should be considered the absolute minimum.

    A better, though more expensive solution is to use a peel and stick membrane. These are much more tear resistant and they will self-seal to nails and screws. Check with the membrane manufacturer about ventilation requirements as these membranes can trap moisture in the attic space if it is not well ventilated.

  1. Keep the design simple. Because these roofs only shed water, intricate trim details are usually not as watertight as those used with water barrier systems. Valleys, hips and other architectural effects can certainly be utilized, but with them comes a much greater chance for water intrusion.

Next post, I’ll get into the applications for water barrier standing seam roof systems

A standing seam metal roof system from MBCI is one of the most durable and weathertight roof systems available in the industry. So when your design requires a roofing system that is both aesthetically pleasing and structurally sound, choose one of MBCI’s six standing seam metal roof systems. Read more.

 

Details, Details, Details

Water runs downhill.  And, gravity is our friend.  Yet sometimes we forget these basic concepts when installing metal panel roofing.

When it comes to metal roofing details, a contractor should always think about the flow of water.

Roofing contractors are in the business of controlling water, so let’s install details that allow water to run downhill and let’s use gravity to our advantage.  A more precise way to say it: Implement drainage details that don’t buck water!

Details, details, details

Defending Against Water Leaks

Metal roof penetration and edge details should not rely on sealant as the primary defense against water leaks.  Certainly, sealant is and should be used as a secondary measure against water leaks.  Consider this: A transverse panel seam is created by lapping the upper panel over the lower panel, and sealant is used as a secondary seal.  Installers would never reverse the lap of a transverse seam (where the lower panel is on top of the upper panel), bucking water and relying only on sealant to keep water out.  A penetration detail (e.g., a vent stack or roof curb) should use the same logic.  There’s no doubt that bad details are rooted in low cost and speed of installation, but those are not details that are going to have equal service life to the metal panels on a roof.  A penetration detail is as critical to the long-term success of a metal roof as a transverse seam.

Prefabricated Penetration Details

It’s best to use prefabricated penetration details that have welded or soldered weathertight seams.  The prefabricated piece should be the width of a panel and include the male and female seams, and be seamed into the adjacent panels.  And just like a typical transverse seam, the top edge of the prefabricated piece should be under the upper panel, and the bottom edge of the prefabricated piece should be above the lower panel.  Water is not bucked and seams are fully intact.  That is a long-term penetration detail.

Where proper overlap can’t happen, redundancy is necessary.  A small pipe penetration detail should use a rubber roof jack with added levels of redundancy for weatherproofing.  First, the roof jack should only be installed in the flat of the panel; sealant tape should be installed between the panel and the roof jack; and closely spaced, gasketed fasteners should be installed to create compression on the sealant.

Roofing That Lasts

Metal roofs sell themselves because metal is long-lasting.  And construction details need to be developed and installed with that in mind.  Metal panels don’t leak—the joinery and fastener locations can leak.  Remember to design and build details that have equivalent service life to the panels themselves.  Proper laps are critical, and remember, gravity is our friend.

To learn how to design a roof system that prevents possible infiltration and allows for proper water runoff, take MBCI’s AIA-accredited course, The Devil is in the Details.

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