AIA Course Number: SMINC00220
Credit: 0.25 LU/HSW
Learning Objective: Following successful completion of this learning program, you will have gained knowledge of what differentiates a standing seam metal roof from an exposed fastener metal roof, and what will determine which system is best suited for your design.
Please Note: After watching the video and reading the text, click the button at the bottom of this page to take the quiz.
You might be thinking: “How different can standing seam metal roofing and exposed fastener metal roofing really be?” The answer is: Very different.
While each system utilizes some of the same materials and ultimately performs the same function of covering and protecting a structure, standing seam and exposed fastener systems are drastically different when it comes to uses, benefits, and drawbacks.
Exposed Fastener Metal Roofing
Exposed fastener metal roofing is defined as a roofing system where the panels are fastened to the structure through the face of the metal and directly into the roof deck or framing below. The panel edges lap one another, and the fastener goes through both layers of metal. It’s called “exposed fastener” because the head of the fastener is visible and not hidden by a seam. An exposed fastener system is typically considered the economical choice of metal roofing and is traditionally used on residential, industrial, and agricultural buildings.
Advantages of Exposed Fastener Metal Roofing
LESS EXPENSIVE – One benefit to choosing exposed fastener metal roofing is that it’s less expensive, especially when compared to standing seam systems. There are many reasons for the lower price, including:
- Wider panels (up to 36”)
- Fewer metal panels need to be purchased and less labor is required.
- Thinner gauge
- Exposed fastener systems generally use thinner and cheaper 29- to 26-gauge metal.
- Lower quality paint systems
- Polyesters and silicone-modified polyester (SMP) paint systems are popular choices for exposed fastener because they’re less expensive than the polyvinylidene fluoride (PVDF) paints typically used on standing seam systems.
- Less accessories to purchase
- Exposed fastener systems are directly fastened down to the structure through the metal, so there’s not a necessity to buy any kinds of clips.
NO SEAMING REQUIRED – Exposed fastener systems do not require hand or mechanical seaming the two panels. Most systems use a lap seam where the edges of each panel overlap the one adjacent to it and are then fastened down together at the same time. This is often why exposed fastener metal roofing tends to be considered the less labor-intensive option when compared to standing seam metal roofing.
PERFORMS RELATIVELY WELL – Exposed fastener systems hold up to weather conditions relatively well, especially if correctly installed for the environment. Since the roof is screwed down the entire width of the panel, there are many solid attachment points to the deck. However, most exposed fastener systems are not engineered to stringent industry standards like standing seam metal roofing tends to be. Panel testing, if any, varies by manufacturer and system type.
MORE CONTRACTORS HAVE SKILLS & TOOLS TO INSTALL IT – Installing standing seam and installing exposed fastener panels require a different skill set, as exposed fastener systems require less attention to detail, less refined installation skill, and less specific installation tools.
PROVIDES A UNIQUE LOOK – Exposed fastener might be considered a more “traditional” look in some geographic areas, specifically rural regions that have a lot of barns, silos, and other agricultural structures.
Disadvantages of Exposed Fastener Metal Roofing
MANY ROOF PENETRATIONS – Exposed fastener metal roofing requires installers to make many fastener holes in the metal that is protecting the structure, which opens the roof up to numerous problems. Most notably: Water penetration and leaking. Since water leaks are a concern, always be cautious of how low of a slope and what type of underlayment you use for exposed fastener roofs.
FASTENER PROBLEMS – Exposed fastener systems put the integrity of your roofing structure in the hands of the fastener and the gasket, which is the thin piece of material located between the head of the fastener and the metal panel. This can lead to many issues, such as:
- Fastener withdrawal – Directly fastening the metal down to the structure without a clip limits the amount a roof can expand and contract, which can cause the fasteners to back out as the metal moves. If the gasket is no longer touching the surface of the metal, there is the potential for leakage at penetration points.
- UV degradation – Exposed fasteners lead to quicker UV degradation of the fastener and the gasket. The time that it takes a gasket to degrade from sun exposure will vary depending on what material the gasket is made of (neoprene, silicone, rubber, etc.)
- Incorrect fastener installation – When you have many penetration points and fasteners, there is more of an opportunity for improper installation of a fastener, such as overdriving, underdriving, or angling.
MORE FREQUENT MAINTENANCE – When compared to a standing seam metal roof, exposed fastener roofs require more frequent maintenance, especially regarding fastener upkeep. This maintenance will include:
- Removing debris.
- Cleaning out gutters and drains.
- Cleaning off dirt, mildew, and other stains.
- Checking for scratches, scuffs, chalking, fading, and flaking.
- Checking for degradation of all fasteners and replacing those in poor condition.
- Making sure all foam closures are in good condition.
- Ensuring that the lapped spots remain water-tight.
NO WEATHER-TIGHT WARRANTIES – Again, putting many holes in something as important as a roof makes it difficult for manufacturers to warrant exposed fastener roofing systems. In fact, we currently don’t know of any companies that offer weather-tight warranties on their exposed fastener profiles/systems.
NO LOW SLOPES – With exposed fastener systems, every panel is lapped and has many screw penetrations through the panel’s surface. You don’t want to take a chance of your roof holding water or having it back up onto the roof system and counting only on sealant or a gasket on a fastener to keep that water out of your building. For this reason, a minimum 3/12 roof slope is industry standard for an exposed fastener system, which will allow the water to shed from the roof.
LESS SLEEK LOOK – Modern architecture tends to focus on clean lines and consistent surfaces, which is something exposed fastener metal roofing can’t offer. The heads of the fasteners raised above the surface of the metal give these systems a bumpier and less sleek look.
Standing Seam Metal Roofing
Standing seam metal roofing is defined as a concealed fastener metal panel system that features vertical legs and a broad, flat area between the two legs. It’s also described as having raised seams, or vertical legs, that rise above the level of the panel’s flat area. Standing seam systems have fasteners that are hidden, whether the panel is attached to the roof deck using a clip or is directly fastened to the deck under the vertical leg utilizing a fastener flange. Standing seam is considered a higher quality system that is commonly used on architectural and commercial buildings.
Advantages of Standing Seam Metal Roofing
NO EXPOSED FASTENERS – Easily one of the most significant benefits of standing seam metal roofing is that no fasteners are visible on the surface, which means they aren’t exposed to UV, moisture, wind, and other elements that can cause a fastener to wear or fail over time. Also, standing seam systems don’t put holes in the panels that are protecting the structure. Plus, some people see fastener heads as unsightly, which is why using a standing seam system to hide them is common.
WARRANTIES – Another safeguard of standing seam systems are the warranties, specifically the weather-tight warranties. Warranties promise that the metal roofing system will not leak or fail during specific weather conditions; if it does, the manufacturer is responsible for remediating the issue.
ALLOWS FOR THERMAL MOVEMENT – When you restrict the expansion and contraction needed for proper thermal movement of a metal panel, you can run into problems, such as oil canning, fastener withdrawal, increased noise, and more. In standing seam roofing systems, the panels generally aren’t double pinned, meaning they can expand and contract better. This is especially true if slider/expansion clips are installed or if it’s a snap-lock system where the metal can move freely with a clip.
LONGEVITY & LIFECYCLE – Metal roofing lasts significantly longer and requires less maintenance, especially when compared to other roofing types, such as asphalt shingles or concrete tiles. Since fasteners don’t penetrate the surface of the metal on a standing seam system, regular maintenance to check for withdrawing, loose, or damaged fasteners is even less frequent.
SLEEK & MODERN ARCHITECTURAL LOOK – Standing seam is becoming more and more popular in architectural applications because of its modern and clean look. In addition to the sleek, straight lines offered by these panel systems, the metal can come in virtually any color, including custom colors, to match any structure. Plus, standing seam systems can be used on structures with many different planes and sophisticated, complex designs, which is another reason why architects often specify these systems.
ENERGY-EFFICIENT – Standing seam systems are frequently made with cool roofing coils that have highly reflective paint pigments and highly emissive metal. This means these systems do an excellent job of reflecting the sun’s rays and dispelling the associated radiant heat that other roofing types may retain. There is also a variety of ENERGY STAR® and CRRC (Cool Roof Rating Council) rated colors and finishes to choose from.
DIFFERENT MATERIAL OPTIONS – Some consumers think that standing seam metal roofing is only available in Galvalume or other steel substrates. In fact, painted aluminum, zinc, and copper are all viable options for standing seam profiles. Remember to look for and ensure that these alternatives are installed to local building codes, as installation methods can vary from steel for these other materials.
MOUNTING OPTIONS – One of the best parts about standing seam is the option to mount items, such as solar panels, snow retention systems, swamp coolers, or other rooftop additions, without penetrating or making any holes in the surface of the roof.
Disadvantages of Standing Seam Metal Roofing
HIGHER COST – One of the most significant drawbacks to standing seam metal roofing is the fact that is can be more expensive when compared to other metal roofing types, especially exposed fastener systems. However, it’s not always the highest price, as metal shingles and other stamped metal materials tend to come in at a higher price, even though stamped materials are often made from 26 gauge or thinner substrates.
LESS QUALIFIED CONTRACTORS AVAILABLE – Hiring a contractor who is qualified, skilled, and experienced in metal roof installation is crucial, especially because standing seam systems require careful craftsmanship. Since standing seam installations may be considered too complicated or tedious, there are far fewer contractors to choose from who have a proven track record and the relevant experience.
LABOR-INTENSIVE INSTALLATION PROCESS – For standing seam roofing, installation is more complex and labor-intensive, as the installation is detail-oriented with clip spacing, seaming, snapping panels together, on-site rollforming, flashings, fabricating/cutting the metal, and more.
NOT FOR USE ON A FLAT ROOFING STRUCTURE – Standing seam systems are not suitable for buildings or homes that have a roof below a .5/12 pitch (mechanical seam). These flatter pitches do not allow water to adequately drain, which could lead to premature degradation, color changes, and the overall failure of the panel system. Furthermore, snap-lock systems should not be installed below a 3/12 pitch.
HARDER TO REPAIR OR REPLACE – If damage or another issue occurs with one panel or a smaller section of the roof, it can be tough to replace efficiently because each individual panel must be separated from the ones that are staying on the structure. This process can be especially tedious for mechanically seamed systems, as each panel will need un-seamed and the sealant will also need to be removed/broken through.
How to Know Which Metal Roof Type is Best for Your Design
Choose standing seam if: You are allotted a larger budget to spend on the roof design.
Choose exposed fastener if: You need to save on expenses and pay a lower price.
Choose standing seam if: The building owner wants to wait longer between scheduled maintenances.
Choose exposed fastener if: The building owner is okay with performing maintenance or hiring a business to perform maintenance, especially on fasteners, an upwards of two times per year.
Slope/Pitch of the Roof
Choose standing seam if: The roof is a .5/12 pitch or higher for mechanically seamed profile and 2/12 or higher for snap-lock profile.
Choose exposed fastener if: The roof is NOT low slope, meaning it’s a pitch of 3/12 or higher.
Choose neither if: The roof is flat. Metal roofing is not recommended for flat roofing structures.
Your Roofing Structure
Choose standing seam if: The building is commercial, architectural, or residential.
Choose exposed fastener if: The building is agricultural, structural, residential, or open-framed.
The Design & Overall Look
Choose standing seam if: You want a sleek, clean, consistent, and more modern look.
Choose exposed fastener if: You want a more traditional look or you don’t mind the visible fastener heads.
Choose standing seam if: Your client wants warranty options, especially weather-tight warranties.
Choose exposed fastener if: Your client doesn’t want a weather-tight warranty.
So which metal roofing type should you choose? It depends on your specific design.
Standing seam and exposed fastener metal roofing both have their pros and cons, but if you know the attributes discussed above, the design your client wants and how to specify the correct roofing system, you’ll be better prepared to make the right choice.