Metal panels need attention; they should not be taken for granted. True, they are a notably long-lasting and attractive choice, particularly with the myriad colors and protective finishes available, but once installed, proper care is imperative in order to maintain their durability, performance and good looks for decades.
What are the main culprits of potential damage? Dirt and residue (such as from trees or animals) left to sit on metal panels, for instance, can cause the irreversible degradation of protective coatings, thereby compromising the longevity of roof and/or wall systems. Additionally, corrosive elements, including bacteria, mold, mildew or even acid rain can damage the structural integrity of the panels. Additionally, buildup of foreign elements, such as leaves, can hide potential leak areas or places that may be rotting away. Even in terms of energy efficiency, keeping the panels clean may help a roof reflect heat as they were originally intended.
To keep panel appearance in top shape, protecting the finishes must be a priority—otherwise, you may find yourself needing to re-coat the panels. Stains from leaves and moisture, algae and lime deposits that remain on panels for extended periods can do serious harm to the finish. It should be noted, however, that re-coating should only be considered if the panels remain structurally sound and if doing so wouldn’t void the manufacturer warranty.
How often should you clean metal panels? Most experts agree that at a minimum, an annual cleaning is advisable in order to keep the panels free of common elements that can jeopardize the integrity of the finishes. If you have heavy tree overhang, you may need to clean it or remove debris a little more frequently.
Deep cleaning to remove more stubborn substances (e.g., tree sap, oxidation) can be done every 3 to 5 years, depending on the building conditions, location and weather, etc. Interim, moderate cleanings can also be performed following substantial weather events and seasonal allergen build-up. It’s a good idea, in fact, to assess roof conditions before winter hits to identify any potential issues that need to be addressed.
No matter the frequency, perhaps the most important advisory when it comes to cleaning the panels is to follow the panel manufacturer’s recommendations regarding who should perform the work and with what solutions and tools so as not to void any warranties. In some instances, it may be beneficial (or perhaps even required) to have a professional building surface cleaning company with metal panel experience do the work.
Tips on Proper Cleaning Techniques and Solutions
As for the maintenance and cleaning instructions, it’s always best to refer to the manufacturer’s guidelines in order to best protect specific products, for example, to determine which cleaning solutions and techniques work best for a given manufacturer’s panels. Neglect or improper care can degrade the finish, compromising not only the visual appearance and performance but, as noted, can also potentially void the panel warranty. But maintaining the panels doesn’t just entail washing them like you would a car; it also means keeping them free of harmful debris.
Here are a few general tips for the proper cleaning of metal panels (again, refer to the panel manufacturer’s specific directions):
Simple cleaning: generally, water and mild detergent will be sufficient. Do NOT use bleach, which can change the finish color or have a harmful interaction with certain finishes.
Water-soluble dirt or other deposits requiring more complete cleaning: you can use a solution of hot or cold water mixed with detergent. In a container of water, use a 5 percent solution of commonly used commercial (non-industrial, non-bleach) mild detergent. Use a cloth or a soft-bristle brush for application of the cleaning solution, followed by a clean water rinse. Alternatively, pressure-washing with a 40° tip is also an option.
Non-water-soluble deposits such as tar, grease, oil and adhesives: a solvent or alcohol-based cleaner may be required. In this case, since most organic solvents are flammable and/or toxic, they must be handled accordingly. Generally, keep them away from open flames, sparks and electrical motors; use adequate ventilation, protective clothing and goggles; and read the manufacturer’s Material Safety Data Sheet (MSDS) of any solvent used for any other specific safety details.
The following are among the cleaners widely recognized by manufacturers for this type of non-water-soluble cleaning: alcohols—denatured alcohol (ethanol) and isopropyl alcohol (rubbing alcohol); and solvents, including VM&P Naphtha, mineral spirits, kerosene, and turpentine (wood or gum spirits).
For any level of cleaning, do NOT use wire brushes, abrasives, or similar tools that will erode the surface coating and leave scratches or other finish damage that can lead to corrosion. Additionally, always test a small area before proceeding with any of the cleaning agents mentioned to ensure there is no adverse effect resulting from the product’s use.
Remember, the misuse or abuse of any of the acceptable cleaning agents will automatically void any manufacturer’s warranty for the affected surfaces, so be sure to check with the manufacturer and also follow directions on any cleaning products used.
By following the tips above, installers can keep metal panels looking great and performing well for years to come.
Metal roofing is a great option for both residential and commercial structures, but beyond just choosing panel type, roof shape options also come into play. Among the most common roof styles in the U.S are a gable and a hip style.
Here we’ll take a quick look at these two distinct styles, explaining key features and differences, and identifying reasons you might want to consider one over the other for a given metal roofing project, depending on your performance or structural needs as well as aesthetic preferences.
A hip roof can easily be identified by the fact in most cases it has slopes of equal length on all four sides, which come together at the top to form the ridge. In many cases, two sides form a triangle shape and the other two sides form a trapezoid shape (e.g., a pyramid shape). A hip roof does not have any vertical ends.
Among the key advantages of hip roofs are they:
• provide greater stability and are more durable than gable roofs due to the inward slope of all four sides.
• do well in areas prone to high wind and rain.
• are typically seen with lower roof slopes.
• allow for more appealing roof lines to be achieved.
Note: For high wind or strong storm-prone areas, proper engineering design, construction and roof system maintenance are especially critical in order to prevent major problems.
Marked by two sloping sides that come together at a ridge, which creates end walls with a triangular extension, a gable roof, also known as a pitched or peaked roof, is easy to spot with its iconic pointed shape.
Among the key advantages of gable roofs are they:
• easily shed water and snow; there is nowhere for water to pool.
• provide more space for an attic or vaulted ceilings.
• allow for more air ventilation.
• are easier and more affordable to build than more complex designs as they need less building materials.
Note: It is recommended to use a steeper slope, for snowy regions.
Breaking Down the Key Considerations
Aesthetics: What architectural look are you trying to achieve? For instance, with more industrial architecture, trapezoidal panels are more common and therefore, a gable roof is a likely choice. In residential situations, where there are more hips and valleys, a hip roof may be a good option.
Building shape may play a role in why you would select a type of roof. If you have a change in building direction, such as an angle, (like an L-shaped building), that’s going to automatically create a valley and a hip on the other side. In this case, you may want to keep that appearance uniform, so you’d put a hip on each end of the building as well.
Also, are you trying to cover up equipment on top of a roof? If so, height differences might play into your decision.
Wind Pressures: On a hip roof, you may have lower wind pressures versus the gable, especially at the corners.
Labor and Materials Cost: The more cost-effective choice would be gable; it is the least costly to install because you’re going to have less material to fabricate a gable roof frame and less waste than with a hip roof. A hip roof is going to utilize more material and more labor because you are going to have more cuts involved.
Panel Profiles: The profile of the panel you’re going with can affect the roof shape choice. For example, for a trapezoidal panel, a gable roof would be a lot simpler to install. Less cutting of the panels is involved and will be easier to seal off the ends of the panels. With a vertical rib or flat pan style panel, it is easier to install on a hip roof application.
Slopes: In general, gable roofs are more likely to be found on lower sloped roofs (less than 3:12) where there are fewer valleys, etc. and therefore, less complicated. Hip roofs, on the other hand, will usually have additional conditions going into them. Valley conditions require a minimum of 3:12 slopes.
When looking at hip roof versus gable, there are obviously a host of factors that will go into that decision. To summarize the differences:
Hip roofs have four faces, are pyramid shaped, and are more complicated to build. They are shown to have higher wind force values. Upfront costs of hip roofs are greater.
Gable roofs have two faces, are triangular in shape, and are easier to build. Upfront costs are lower.
In many cases, it should be noted, most roofs feature numerous details and can include both hip and gable roofing.
To learn more about hip and gable roofs for your next metal building panel project, contact your MBCI local sales representative.
Whether it is wind speed, sun exposure or the proximity to a coastline, these factors would be the major considerations when choosing metal roofing for a project in coastal areas. The good news is that metal panels can be used in just about any coastal area so long as you find the right product profile and finish that meets your specific requirements to maximize performance given the variables of the environment.
There are a number of special considerations given the environmental conditions inherent to a coastal area, including the impact to paint systems and certain unique maintenance requirements, wind ratings, hurricane conditions and certifications/regulatory product approvals that will limit the panels you can you use within specific coastal areas, for instance Dade County, the state of Florida, and the Texas Coast.
Finishes: The 1,500-Foot Rule
Metal components can be a great roofing choice, even in a coastal area, whether a bay, gulf, or ocean water. Key is how you manage the finish on the products and how close you are to the actual salt environment. Simply stated, if you’re outside of a 1,500-foot range from the coastline or salt water, then standard metal roofing would be suitable, but if you’re closer to the coastline there are special paint options or finishes you’d need for the product to withstand the coastal environment.
At MBCI, we use Flurothane Coastal coil coating system* as our standard solution to the challenge of salt spray and harsh coastal environments. This coating is a premium fluoropolymer (PVDF) system developed for use in the most extreme coastal environments. This system is unique in its use of an innovative thick film primer. The two-coat system has a total dry film thickness (DFT) of 1.7 to 2.0 mils.
Choosing an appropriate coastal finish can also affect your product’s warranty. If, for example, your project is within the 1,500-foot range and you don’t choose the required coastal finish, if the panels were to rust there would be no warranty offered and it could affect your warranty for weathertightness as well.
Suitable Panel Types and Additional Coastal Conditions
Overall, roof failures are the largest hurricane loss due to wind and water damage. For this reason, metal roofing is a highly recommended option for coastal regions where hurricanes and high force winds are prevalent. The appropriate metal panel type for these areas is mainly contingent upon what you want to accomplish. Because MBCI does have high wind ratings for most of our panels, whether it be a screw down (aka through-fastened) panel or a standing seam profile panel, selections should be determined by the complexity of the roof itself and the roof conditions. There are standing seam panels and through-fastened panels that can be approved for both roof and wall applications in many coastal areas.
Also, of note, different types of coastal areas may receive higher wind speeds. There is obviously a wide difference in wind speeds between the East Coast and the West Coast, for example, although both are coastal communities. In an area with higher wind speeds and/or hurricane conditions, you would want to consider panels that achieve higher wind ratings. Since there are many different panel options, and some may not be able to achieve as high wind ratings as others, you should look at what those values would be for wind and what testing has been done. MBCI’s metal wall panels and roofing systems are able to resist and withstand extreme environmental conditions, such as those in Florida or the Texas coast where strict product approval and testing processes are required.
MBCI has panels that meet requirements for Florida Approval, Dade County and Broward County for instance, where you need to have an NOA (Notice of Acceptance) for those county areas, as well as products that are TDI approved (Texas Department of Insurance), which is usually seen in the Texas coastal area.
Additionally, sun exposure and color can have an impact as far as solar reflectance, so that is another consideration. Somewhere like Florida gets a lot of sun yet a coastal area in Washington State would be mostly cloudy. If you are in an area that has more sun, then you may want to consider a panel with a higher solar reflectance value.
If you have metal roofing in a coastal area, you’re going to follow much of the same maintenance as you would on any metal roof, but you would want to inspect it for damage, especially after a wind event or storms. One of the main differences, though, especially if you’re within the 1,500-foot limit where you needed a special finish, is that you’re going to have to do a fresh water rinse regularly on the panels a couple of times a year. What this means is you are basically hosing it off with fresh water to get the potentially corrosive salt spray residue off of it.
For more on metal roof and wall panels and finishes for use in coastal areas, contact your local MBCI representative.
* (1) All substrates must be properly pretreated. (2) American Society for Testing and Materials. (3) Flurothane Coastal system is not designed to bridge cracks in the substrate. (4) Varies by color. (5) Flurothane Coastal system will generally meet the requirements for most post-painted fabrication processes. However, variations in metal quality, thickness or cleaning/pretreatment applications can lead to diminished flexibility.
SOURCE: Valspar Corporation
It would seem logical that the most important field installation process for a standing-seam metal roof is the actual process of creating the weathertight seams that connect the metal panels together and ensures the structural integrity of the roof. Perhaps for many different reasons, however, this critical seaming process is not always given the proper attention it deserves, nor are installers given the proper training required to ensure installation runs smoothly. This approach can cause some serious issues, not the least of which is the voiding of a manufacturers warranty or the discovery of roof leaks and the resulting damage.
To help, here are some best practices for readily and successfully carrying out the metal roofing seaming process:
Because of the critical nature of seaming metal roofs, the crew members doing this work should be properly trained. Team members who will be performing this work should not perform the seaming without having participated in the appropriate installation training required to ensure the seaming process is appropriately managed. Most roofing manufacturers offer installation training that many installers take advantage of—and this training opportunity should be taken advantage of by the staff who will be doing the seaming.
It is very important that the seaming equipment being used is matched to the specific roof panel system being installed. Manufacturers routinely rent out this equipment in order to be sure that the metal panel profiles are installed properly and are not compromised through the use of generic equipment or that of another manufacturer. Using the wrong equipment can end up being costly for everyone if panels and seams are ruined in the process.
As metal panels are set in place, they are often secured with metal clips, spaced according to engineering and construction needs. Hand crimpers are used to form the seams around the clips as well as any end laps. This process must not be overlooked as improper hand tooling is the number one cause of faulty seaming. To ensure costly mistakes aren’t made, follow the process described in the “Field Seaming Tool Manual”. This manual should be provided with the equipment and reviewed in training.
The next step will involve the use of an electric seamer which obviously needs a source of electricity to operate. However, not just any electrical power source will do. Almost all professional seamers have an AC/DC motor that will require 10 or 15 amps and 120 volts. A dedicated electrical circuit—preferably from a temporary electrical pole or an existing building electrical panel—is the best and most reliable way to go. A generator with 15 amp capacity dedicated to be used only for the seamer (in order to avoid power surging) may be acceptable as well. In either case, the power line to the seamer needs to be 10-gauge (minimum) cord. It should also be no more than 200 feet long (to avoid power drop).
Electrical power sources that are NOT acceptable include outlets from a powered man lift or a generator that is not dedicated to only the seamer. (This includes a generator that is part of a welding machine.) Check the manufacturer’s requirements for any other restrictions that can damage the seamer. Skipping this step can place the responsibility for repair or replacement onto the installer.
Once all panels are in place, the hand crimping is done and the power source is set. Then, electric seaming takes care of finishing the roofing system. Again, consult the seamer manual for proper procedures, including which direction the seaming should be done. (Seaming can either be done up or down the roof depending on direction of roof installation.) The electric seamer includes a switch for the operator to control the starting and stopping of the process.
On low-slope roofs, the operator should walk alongside the seamer to be sure nothing is in its path and that the seam is done properly. While stopping and re-starting is fine, the seamer should never be removed in the middle of a seam. Doing this makes it very difficult to set it back in exactly the same spot again. If something appears to be wrong with the seamer or the seams being produced, then don’t keep using it. There is no point in damaging multiple roof panels if any one panel indicates that things aren’t going right. In this case, contact the manufacturer right away for assistance or replacement of the seamer.
Electrical seamers are heavy and—if not used and secured properly—can cause harm or injury. Therefore, they should always be tied off with a safety line—the same type used for workers—not a common rope and definitely not the electrical cord. The safety line should be properly secured to the seamer and then attached to something rigid on the building. Never attach this to a person who could be pulled off of a roof by it.
Before use each day, check the electric seamer and remove any oils, debris or dirt. Make sure the seamer is unplugged from the electrical power source before you begin cleaning. Also, check the grease level in the machine daily and only add a little bit (2-3 pumps from a grease gun) as needed. Too much will cause the grease to leak out onto the roofing.
Following these pointers should help assure the safe and efficient use of the right seaming equipment when installing roofing panels. To find out more about proper seaming or to schedule training, contact your local MBCI representative.
With the great variety on the market, one of the main questions we, as metal roof panel manufacturers, get from customers is “How do I select the right panel for my project?” The answer can generally be found by examining a number of criteria, including the properties of the roof, the region and climate, geometry, slope, warranty type…among other key factors.
Here we will provide a brief overview of the various factors that should be considered when narrowing down the choices.
1. Slope— Slope is the first consideration as just this one aspect will eliminate certain panels, making it easier to narrow down options right from the start. The two types of roof slopes are low slope and steep slope.
- A low-slope roof, commonly found in commercial applications, is one whose slope is less than 3:12. The benefits include a simpler geometry that is often much less expensive to construct, and the requirement of fewer materials than a steep slope, thereby reducing material costs.
- A steep slope roof, more common in residential construction, 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. Since the roof is a visible part of the structure, choosing a metal roof for residential construction often skews more toward aesthetic considerations.
2. Location/Climate— The location and climate of the project is a factor, specifically when looking at certifications/regulatory product approvals, which will limit the panels you can you use within specific regions. This is most relevant to Dade County, the state of Florida, and the Texas Coast, as well as certain snow regions.
3. Specified test standards—Often times, you may need to specify UL 580 or Factory Mutual Insurance Design.
4. Engineering Design—Due to the roof pressure acting on the buildings, engineering design factors eliminate some products because they’re simply not strong enough. This is an area that needs true technical expertise. For that reason, make sure to get a professional engineer to design the roof system in order to determine the correct panel for the project. Also, check with the manufacturer to determine if they have panels that have been tested to certain test standards. If they do not have the testing on a product, that in itself can exclude a particular panel.
5. Geometry—In its most basic terms, roof geometry is an overview of what the finished roof will look like, including special conditions, such as hips, valleys and ridges. The various conditions that go along with specific roof types will determine if a roof geometry is simple or complicated—which will affect the type of panel that can—and can’t—be used. For instance, a Double-Lok® roof panel can be used on a low slope roof—it can go down to 1/4:12. However, if a low roof slope condition has a valley, you may want to avoid a Double-Lok® panel since this product is more difficult to use in a valley situation.
6. Panel type— Panel types can be broken out into two main types: standing seam and through-fastened. The choice of specific product within these general categories depends on a number of considerations, including aesthetics and weathertightness warranties. If your project calls for either standing seam OR through-fastened, that will eliminate about half the types right off the bat.
- Standing Seam Roof Systems
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.
- Through-Fastened Roof Systems
Exposed, or through-fastened panels, are available in a variety of widths, usually from two to three feet wide. They also come in various rib shapes, heights and spacings. Typical gauges are 29 and 26, but they also come in 24 and 22 gauge. There are also structural and non-structural through-fastened panels. Structural panels are capable of spanning across purlins or other secondary framing members such as joists or beams. Non-structural panels must be installed over a solid deck. Through-fastened roofs are best suited to small- and medium-sized metal buildings and residential applications. In both instances, the panel runs are limited to shorter lengths where thermal movement is typically not a problem.
7. Substrate— Examples of substrates are open framing, plywood, and metal deck. Some panels can’t be attached, for instance, to open framing but almost every type of panel can attach to plywood.
8. Required Weathertightness Warranties— If a weathertightness warranty is a requirement, your options are down to the only panels offered with that guarantee—eliminating all the through-fastened panels.
Looking to the Manufacturer for Help
While specifiers need to take that initial look at all the determining factors, the choices can still feel overwhelming. Once you’ve eliminated the panels that surely won’t work, you will still likely be left with many strong choices. The metal panel manufacturer can guide you to that decision. We encourage you to contact the MBCI team of experts to help further narrow down the choices in order to finalize what is the best metal roof panel for your project. For more guidance on finding the right roof panel for your project, stay tuned for our white paper coming soon.
Sloped, standing seam, metal roofing provides a continuous surface that is designed to shed water efficiently while providing a long-lasting and great looking roofing solution. When the roof design and shape is simple, (i.e. continuously extending from ridge to eaves with no changes or interruptions) then all of the attributes of the metal roofing can be assured by using some very conventional and well-known details for design and construction. But in the real world, there are lots of conditions that require more specialized attention to detail. For our purposes here, we will simply refer to those as “specialty roof conditions.”
What types of roofing conditions warrant the special attention? Most are associated with changes in the shape or surface of the roof, say where the ridge line is interrupted or offset. Others could be a means to accommodate a roof feature such as a dormer, a dutch hip type of roof, or the intersection between a ridge and a parapet wall. Some might be related to the design of a valley, particular if it is a “dead valley” that doesn’t drain directly to the gutter but stops short, as around a dormer or elsewhere. Or some could be the result of some special conditions created by the roof design such as cascading water over an edge or heavy snow accumulation conditions. There are certainly many others too, but the point is that any of them are a potential source of water leakage and building damage if they are not properly addressed.
Most metal building manufacturers not only recognize the importance of such specialty roof conditions, but they also have lots of experience in developing very workable solutions for them. The key for success is found in the fundamental principles of properly overlapping (i.e. “shingling”) all materials to allow water to drain smoothly away where it is intended without getting diverted to places where it shouldn’t go. That means the metal roofing panels need to be cut, fit, and installed properly, but it also means that flashing, sealants, and fasteners need to be installed correctly too, all regardless of the slope of the roof. To communicate ways to achieve better results in the field for specialty roof conditions, manufacturers like MBCI make step-by-step details available for installers. The significance of using and following these details can not be overstated since they are a key component in getting a weathertightness warranty from the manufacturer.
As an example of how this might play out on a specific building, let’s look at a dead valley that occurs because a gable roofed dormer is installed in the main area of a roof. The first thing to recognize is that multiple layers of materials are involved in the transition around the dormer, all of which need to be installed in the proper location, following the proper sequence, and with the proper connections. A step-by-step process as detailed by the manufacturer might look like this:
With the substrate in place (rigid insulation over a metal deck), a special width panel will likely need to be installed and serve as the collection area for the dead valley to drain into. Then, plywood spacers and nailers are installed, and the main lower valley area is covered with “rubber” (EPDM) flashing.
Secure continuous eave trim over the plywood nailers and add and offset cleat on top to receive roof panels, all secured with tri-bead tape sealer and fasteners as shown.
Install extended valley trim across the valley with an offset cleat on either side secured as shown.
With all of the prior steps in place, then the installation of upper panels can begin to interface with the edge of the dead valley.
Continue cutting and installing panels to fit over and drain into the dead valley, which then drains without interruption onto the special width panel and the roof.
By following step by step details from the manufacturer for this or other specialty roof conditions, then the likelihood increases that everyone involved in the project is both proud and satisfied with the end results. The key is to start at the beginning with the proper planning and preparation by communicating with the manufacturer about all roof conditions that require special attention like this example.
To find out more about the library of specialty roof conditions available for metal roofing projects, contact your local MBCI representative.
One of the most misunderstood aspects of a metal roofing system is the proper use of a vapor barrier. There are many sources of information about this topic – some of which are based on science, some based on anecdotal field experience, and some based on journalism. Here, we will try to break it down to the basic principles that can be used to understand the latest options for a metal building roof system today.
What is Vapor?
The observed science tells us that water can take three forms, depending on temperature and its ability to interact with other things around it. Water can be a liquid that we drink, solid ice that we can skate on, or a gaseous vapor that is part of the makeup of the air we breathe. We can’t see water vapor in the air but we can feel it – we call that humidity. High humidity means a lot of water vapor is in the air, typically coupled with higher air temperature – and both can make us feel uncomfortable and “sticky.” Low humidity means the air is dryer – more typical in lower-temperature air – but this may also be uncomfortable for our breathing, skin dryness, etc.
Why is Vapor a Concern?
As long as the gaseous water vapor stays in the air at a moderate or comfortable level, there is no real concern. However, since water vapor responds quickly to temperature, it can turn back into water as soon as it encounters a surface that is cold enough for it to make the transformation. We know this phenomenon as condensation, and anyone who has seen a cold drink collect water on the outside of a glass on a humid summer’s day has experienced it. It is the same phenomenon that shows up on the surface of windows in a building when there is a big difference between inside and outside temperatures. We know that the amount of water vapor (i.e., humidity) present and the air temperature can both be variable at any given time, but there is always a predictable point at which water vapor will condense and form water drops – this is called the dew point. When vapor in the air encounters a temperature at or below the dew point, condensation occurs.
What Does This Have to do With Metal Roofing?
Metal roofing systems and condensed moisture are not a good combination. If airborne moisture seeps into a metal roof assembly, finds a cool surface, and condenses on any surface there, it likely won’t be visible from inside or outside of the building. That trapped water can then cause rust and corrosion of metal parts, resulting in real damage. It can also collect and saturate building insulation, rendering it ineffective. If enough water condenses, it can cause visible staining or grow mold, causing concerns for people inside the building.
Do Building Codes Address This?
Absolutely – they require that the building be protected from the possibility of damage caused by water vapor. Since the concern is to restrict the flow of airborne moisture in relatively warm air from reaching a cooler surface to condense on, they call for something to be installed on the “warm” side to prevent that flow. For most buildings across the United States, the warm side is the interior face of the roof and walls. However, if the building is kept cold as in a refrigerated warehouse or storage building, then the warm side is likely on the exterior. The same is true in southern climates where warmer, humid air is the exterior condition and cooler interiors are common.
What is the Best Solution?
Manufacturers of insulating products have been involved in addressing the best ways to provide not only insulation to keep building temperatures warmer, but also vapor barriers to restrict the flow of airborne moisture. After literally decades of trying different types of vinyl and polyethylene facings over fiberglass insulation, most have realized that those membranes simply don’t provide enough protection to be effective. Instead, most are now offering a choice of laminated facings over the insulation that can be installed so they are exposed to the appropriate warm side of the roofing system. These fairly sophisticated laminations include:
- Polypropylene-scrim-kraft consisting of layers of white or metalized polypropylene, fiberglass reinforcing, and white kraft paper on the order of 11-30 lb. weight
- Polyprolene-scrim-kraft consisting of aluminum foil, fiberglass reinforcing, and 30 lb. kraft paper
- Vinyl-reinforced polyester
All of these latest advancements in vapor barriers can provide comparable, high levels of protection, but their selection can depend on a variety of other building factors. Therefore, it is always best to engage an architect or engineer in the design to review the needs of the entire building to select the most appropriate, specific solution for an given project. It will also be important that all seams, connections, and penetrations of the vapor barrier are addressed in the design and construction, which are similarly best addressed by an architect or engineer to assure there are no breaches in the protection provided by the barrier.
Installing metal roofing and siding requires placing and aligning metal panels over the structural supports. But ultimately it requires installers to spend a fair bit of time fastening them in place, typically using a great many fasteners. It is easy to get complacent about this repetitive activity, but the reality is that every fastener plays a crucial role in the integrity and longevity of the installation. Properly selecting, installing, and using the right tools, allows for a proper fastening process that assures a weathertight installation. But if a few fasteners are installed poorly, causing water or air leaks, then the installer is called back to correct the condition. Do a lot wrong, and warranties can be void, with the durability of the building left compromised, possibly requiring a total do-over.
What’s the difference between a good fastening installation and a problematic one? Here are some of the things to pay attention to onsite:
The most common type of fasteners used in metal buildings are self drillers, which vary based on diameter, length, head shape, and material. They are also specifically designed for use in metal substrates. Different fasteners are also available for wood versus metal, and either type can be sized for different substrate and panel thicknesses. Zinc alloy or stainless steel fasteners are common choices for durability, longevity, and avoiding galvanic action with other metal products. Selecting and using the right fastener type for each of the different locations on a metal building begins with determining what is being attached and what is it attaching to.
Fasteners of any type cannot be relied upon by themselves to keep out the elements. Instead, a sealing washer is used that is compressed between the fastener head and the metal panel as the fastener is tightened to form the weathertight seal. High-performance or long-life fasteners may be required for a durable approach to weathertightness and/or may be required by the metal building manufacturer to receive a weathertightness warranty.
With the right fasteners onsite, the success of the installation now rests with the field crews. A few minutes to review the different fasteners and match them with the right tools and settings for installation is time very well spent. Since electric screw guns with or without impact drivers are common on the jobsite, it’s easy to think any tool will do, when it probably won’t. The wrong tool at the wrong setting can place too much torque or other force on the fastener, causing it to crush or damage washers or even the metal panels. Impact drivers are rarely needed in most cases and, while the fastening needs to be tight, overtightening is never a good thing.
In addition to weathertightness, fasteners provide a structural function as well. Their location and spacing will directly correlate to the ability of a panel to resist wind and other forces after installation. Therefore, it’s always best to use information prepared by a professional engineer on the proper fastening locations, spacing, and sizes. The calculations behind such information can prove to be the difference between a successful installation and one that creates problems.
Understanding the importance of fasteners and the role they play in the integrity of the building, and corresponding warranties, allows installers to see beyond the repetitive task of fastening and into the craft of assembling a durable, long-lasting building. To find out more about fasteners for metal products and systems for your next project, contact your local MBCI representative.