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.

Planning for Metal Roofing Retrofits

The decision to retrofit an existing commercial roof with a new metal one is usually based on the very real appeal of creating a long-term (50-60 years) roofing solution, achieving better energy efficiency, creating better aesthetics, or all of the above. Prior blog posts discussed these benefits in more detail and talked about different types of metal roofing retrofits. Here, we will focus on where to start in terms of planning to undertake a roofing retrofit based on covering a membrane roof with a metal-framed, low-slope, metal roofing system.

Existing Building Assessment

A successful retrofit is based on the new metal roof system working with the existing building structure and local conditions. Each of the following should be looked at first when starting the planning and design process:

  • Existing Roof Geometry: The shape (length and width) of an existing roof is important to determine the square footage of the roof, but so are the actual dimensions, since those can impact the height of the new metal roofing. The minimum recommended slope for new roofs is between ¼:12 and 3:12 , depending upon the roof system chosen for the new roof. Existing roof details such as overhangs, parapets, and the existing roof slope itself all need to be documented in order to determine how best to address them with the retrofit system.
  • Existing Roof Type: In many cases, the existing roofing does not need to be removed, but there may be ballast such as stone or other materials that are no longer needed. Oftentimes, the removal of this ballast will compensate for the additional weight of the new roof and framing system. The materials of the existing roof may also pose compatibility issues with new materials, so they should be documented to plan accordingly.
  • Existing Roof Substrate: Under the existing roofing, some type of substrate material is holding it up. It may be rigid insulation resting on a metal, wood, or concrete deck, or it may be an uninsulated substrate that has insulation below it. The specifics here need to be established, since the new metal framing will need to connect through this material. If insulation is in fact part of the substrate, then its effectiveness should be determined—has it gotten wet and been compromised, or is it still in good usable condition? Either way, how much is there?
  • Existing Roof Structure: The structural system of the building includes framing or other components that support the roof. This is what the new metal framing will anchor to and transfer structural loads to. Hence, the specifics in terms of type (steel joists, concrete beams, wood joists, etc.), the size, and the spacing are critical. Further, the carrying capacity of this system should be assessed and analyzed by a structural engineer, since the retrofit system will add 2 to 4 pounds per square foot of dead load to the roof structure. Further, this weight, plus any live loads from the roof, will typically not be distributed uniformly, but in a series of point loads. Therefore, the engineered capacity of the existing structure needs to be known to determine if any structural enhancements are needed.
  • Existing Roof Equipment: Many commercial buildings use the roof to locate mechanical, electrical, or elevator equipment. In some cases, that equipment can be moved to the ground or elsewhere, but in other cases it can’t, or would be too costly to consider. Hence the details, location, and height of such equipment needs to be known so a determination can be made on whether it can be covered and enclosed in the “attic” of the retrofit system, or if it will need to be raised to the top of the new roof.

New Retrofit Roofing Goals

With an assessment of the existing conditions in hand, the focus now becomes identifying the primary objectives of the new roof. These should be clearly articulated so the final design can address and include each of them:

  • Appearance: What is being sought in terms of shape, height, visibility, color, improved curb appeal, or other visual considerations?
  • Performance: What is the new roof being asked to address related to operations or performance issues? Common elements could be improved drainage, less maintenance, greater longevity, or more resistance to damage.
  • Energy Efficiency: Replacing a roof is the ideal time to improve energy efficiency in a building by adding new or more insulation. This could be done simply to meet current energy code requirements or to contribute to an overall energy-use reduction project at the building. In some cases, the new roofing system could enhance the ability to include energy generation, such as solar panels mounted to the new roofing system.

With proper planning and goal setting, a metal retrofit system can meet or exceed all expectations. This was the case recently at a water treatment facility in Dallas, Texas. Here is a photo of the existing built-up roof that was experiencing problems and needed replacement. It was assessed, analyzed and determined to be an excellent candidate for a retrofit metal roofing system.

Retrofits

 

Metal Roofing Retrofits
Here is a photo of the light-gauge metal framing installed to create the new low-slope planes and transfer loading to the existing building structure.

 

Planning for Retrofits
And, finally, here is the completed metal roofing, which looks better and is expected to perform better than the original roofing.

 

To learn more about MBCI retrofit metal roofing systems and how they might work on a building you are involved with, visit http://www.mbci.com/products/retrofit-products/.

Benefits of Roofing Retrofits with Metal Roofing Systems

Many commercial buildings, and even some residential ones, have low slope or “flat” roofs that can be problematic to maintain. They typically rely on a membrane of some sort that in and of itself is waterproof, but every seam, penetration, flashing, and other detail is a potential leak if not installed and maintained properly. Further, the subsurface that the membrane sits on determines the actual slope to roof drains so if that is compromised, then standing water can sit on the roof and cause issues. Even the roof drains are a concern if they get clogged with debris or leaves and cause water to back up and stagnate on roofs.

Given the potential difficulties, and the frequency of replacement that is often needed for flat roofs (average of 20 years), it is no surprise that many facility managers or owners look to retrofit their buildings with sloped metal roofs wherever the size and geometry are conducive to it. In doing so they recognize the many benefits obtained which can include any or all of the following:

Reduced Maintenance with Metal Roofing

A complete metal roof system (e.g. metal framing, metal roofing, insulation, and ventilation) can be designed and installed to require minimal maintenance. That means not only fewer potential problems, but reduced operating costs over the course of many years.

Increased Roof Lifespan

Metal roofing is recognized by industry experts for having a very long lifespan even under challenging weather conditions. It is not uncommon for a metal roof system to last 60 or more years compared to a 20-year average for flat membrane roofs. If Galvalume® coated steel is used (i.e., zinc/aluminum coating licensed to roofing manufacturers), the roof lifespan can be expected to last the full service life of the building, according to studies done on standing seam roofs by the Zinc-Aluminum Coaters Association and the Metal Construction Association (MCA). Long-lasting roofing means there is only one installation to provide and pay for, not multiple ones over the life of the building.

Retrofit
Tum-A-Lum Lumber featuring Retro-R® Metal Panels

Improved Building Energy Efficiency

Retrofitting with new insulated metal roofing systems is an excellent solution to high energy consumption and associated costs in a building. Retrofit systems can be designed to work over existing flat roofs or even over older sloped metal roofs to upgrade a building to meet or exceed current energy code requirements. Such systems add insulation between the old and new roof reducing heat gain in summer and heat loss in winter. The metal roofing can also be finished to reflect the heat of the sun away, achieving  higher solar reflection index and reducing cooling costs.

Greater Sustainability

In addition to energy efficiency, metal roofing systems can be made from recycled steel and then be re-used or recycled at the end of its service life. This capability helps reduce the amount of material headed to landfills and can contribute to points in the LEED green building rating system, among others.

Improved Aesthetics

Sloped metal roofs can be used as a significant design feature on many low rise and mid rise buildings. The range of colors and textures provides architects and other design professionals a full palette of options.

Increased Property Value

Curb appeal and long term performance are common contributers when a property is being assessed for value. A retrofit metal roofing system can certainly help in this regard.

Overall, there are many reasons for choosing a retrofit system for an existing building. Whether to replace a leaking roof, correct the current geometry, meet new regulation or code requirements, improve the aesthetics, or increase the energy efficiency of a building, all of the benefits above can be realized. To learn more about MBCI retrofit metal roofing systems and how they might work on a building you are involved in, visit www.mbci.com/products/retrofit-products.

Choosing the Right Type of Standing Seam Roof (SSR)

When it comes to specifying standing seam roofs, one type doesn’t fit all. While a standing seam metal roof system can be one of the most durable and weather-tight roof systems available in the industry, its benefits can be negated if you fail to understand the details in application parameters of the specific system. Do your research, though, and for your next design that requires an aesthetically pleasing and structurally sound metal roofing system, you can choose with confidence the standing seam metal roof system that suits your project to a tee.

How to identify a good standing seam roof system

A good standing seam roof system is one that can satisfy both the project’s specific design criteria and adhere to building code standards. Standing seam profiles can include those that are utilitarian or architectural in nature, are of numerous widths and profiles and have varying seam joinery (e.g., snap or field seamed).

Why specify a standing seam metal roof system

When properly installed, standing seam metal roof systems are an extremely effective and long-lasting material choice. Key advantages include:

  • Weather-tight roofing system
  • Can be engineered to withstand high winds (150 mph and higher)
  • Class A Fire-resistance rating from UL
  • Class 4 Impact-resistance rating from UL
  • Long service life—up to 60 years
  • Lightweight
  • Special clips designed to accommodate thermal roof expansion and contraction and various thicknesses of fiberglass insulation

Matching the roof system to the project

In basic terms, there are four unique styles of metal standing seam panels: Double lock seam, symmetrical seam, one-piece snap-lock interlock and two-piece snap-lock interlock. These styles can be further delineated by seam shape or profile, i.e. trapezoidal rib, vertical rib, square rib and tee rib. The choice of the rib profile, as well as the rib spacing is generally an aesthetic preference of the designer. Knowing which style will best suit a given situation will help ensure a successful installation.

Popular Standing Seam Metal Panels

Double Lock Standing Seam
Shown: MBCI Double-Lok®

One-Piece Snap Lock Interlock Standing Seam
Shown: MBCI LokSeam®

Two-piece Snap Lock Interlock Standing Seam
Shown: MBCI Craftsman™

Some criteria to consider are roof slope, roof run (distance from eave to ridge), weather conditions (such as ice or snow) and architectural features, i.e. hips, valleys, dormers, parapet walls, etc.

For instance, if your project has a roof slope of 1/2:12 you will need to ensure the product being installed is approved for this low pitch. In this case, you would likely use a “double lock” or mechanically “field-seamed” panel. You also want to ensure that all details are able to provide for a weather-tight seal even if temporarily submerged during a heavy rain. Field-seamed panels are also the best choice in areas that experience heavy ice and snow.

Additionally, it is imperative to recognize complicated design details that should be carefully specified and reviewed regardless of the roof slope. Design conditions that require special attention include: roof transitions, dead valleys, dormers, eave offsets, ridge offsets and offsets in parapet walls.

It cannot be overstated that you should always consult a metal roofing manufacturer about the capabilities of the standing seam metal roof system, including what warranties are available, prior to specifying it.

Browse the standing seam product manual for more information.

Design and testing

Familiarize yourself with wind uplift testing as prescribed by Underwriters Laboratories (UL-90 – 580 Test) and ASTM E-1592.

For more information on standing seam metal roofing, visit MBCI’s CE course on the topic: http://www.bdcuniversity.com/standing-seam-metal-roofing

Installing Metal Roofing Over Asphalt Shingles

Can Metal Roofing Be Installed Over Shingles?

When an asphalt shingle roof wears out, one of the most long-lasting solutions is to retrofit the roof with metal panels, and not remove the asphalt shingles.  While it’s a change of appearance, the metal roofing panels will provide a greater durability and longer service life.

UCI
UCI Retrofit Corporate Office installed 7.2 roof panels over the existing asphalt shingle roof

Installing Metal Roof Panels Over Asphalt Shingles

There are a number of considerations when installing metal panels over an existing asphalt shingle roof.  First, the building codes allow metal over shingles if there is only one layer of asphalt shingles.  A third roof is not allowed, so there must only be one shingle roof in place.

If you’re considering installing metal roofing over asphalt shingles, contact us today to learn more about MBCI’s panel systems.

Choosing the Correct Retrofit Metal Roofing System

Fastener choice is important for wind resistance.  As is the pull-out resistance of the deck. The panel thickness (e.g., 24 gauge), panel width, height of the standing seam, spacing between clips, and clip strength all help determine the overall wind resistance of a metal panel recover installation.  Wind design loads are specific to geographic location and height of the building; work with the metal panel manufacturer to determine the design specifications.  Importantly, use fasteners that are long enough to penetrate through the asphalt shingles and the deck by at least ½” to ensure proper strength.UCI_2

 

Because metal panels run from eave to ridge, the flatness of the existing roof can affect the appearance—the waviness—of the metal panels.  Three tab shingles are quite flat versus laminated dimensional shingles.  Consider installing a base sheet or a #30 underlayment over the shingles before installing the re-cover metal panels.  The uneven surface of the asphalt shingles can be telegraphed to the metal panels, leading to an uneven or wavy surface of the new metal panels.  And, like oil canning, it’s not a performance issue, but homeowners don’t want an unsightly roof.  Spending a few dollars on a heavy base sheet/underlayment is cheap insurance to ensure an aesthetically pleasing roof, and that means a satisfied homeowner who is willing to pay for the new roof!

Benefits of Installing Metal Roofing Over Shingles

There’s a sustainable advantage to installing metal over existing asphalt shingles.  Not removing the asphalt shingles not only saves money but also reduces the amount of waste sent to a landfill.  Roofing tear-off is one of the largest contributors to landfill waste in the U.S. And, while there’s a lot of discussion about the reuse of asphalt shingles (i.e., downcycling) in asphalt roads and bike paths, the reality is that much of the shingle tear-off is not actually reused.  For example, the Colorado Department of Public Health and Environment no longer considers asphalt shingle waste to be a recyclable material.  Not because it’s not recyclable, but because there is no significant market for its use.  These ideas will influence some homeowners, so use them when selling the idea of recovering with metal.

Installing metal panels over existing asphalt shingles is a smart choice.  Design it right, and the new metal roof could last the life of the house.

Contact us today to learn more about how our panels can be installed over asphalt shingles.

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