Metal roofing can withstand Mother Nature, from hailstorms to hurricanes. This type of roof is better suited to membrane roofing than shingles. However, as with all products, problems can still occur.
Most issues with metal roofing stem from installation errors, incorrect panel profile selections, side laps, and fastener locations on lower roof slopes.
The roof slope, or pitch, is the rise or fall over 12 inches of run. You typically see slope written numerically, such as 1/12 or 1:12. This means the roof rises in inches per 12 inches of run toward the ridge. Most metal panel manufacturers publish minimum slopes for various panel styles on their websites.
WHY SLOPE IS SO IMPORTANT ON A METAL ROOF
A roof’s slope determines how quickly water and snow shed and dictates the required metal panel system. Most metal roofs require a minimum pitch of \(3:12\) (rising 3 inches for every 12 horizontal inches). Steeper pitches (\(> 3:12\)) excel in shedding water, while specific standing-seam systems can accommodate pitches as low as \(1/4:12\).
CLASSIFICATIONS AND PANEL TYPES
The slope of your roof defines whether it falls into the low-slope or steep-slope category. This classification determines how the roof sheds or holds water:
- Low-Slope (\(< 2:12\) pitch): Requires a hydrostatic, water-holding system. These roofs handle slow-moving water and require mechanically seamed panels with high-performance sealants to prevent leaks.
- Steep-Slope (\(> 3:12\) pitch): Requires a hydrokinetic (water-shedding) system. Water moves off these panels much faster, allowing the use of snap-lock systems instead of mechanically seamed ones.
YOUR ROOF PITCH MATTERS
- Water Drainage: Flatter roofs have a higher risk of standing water (ponding), which accelerates corrosion and degrades seams. A proper pitch ensures rainwater flows effortlessly into gutters.
- Snow Management: In snowy regions, a steep pitch is critical for shedding snow effectively. However, extremely steep metal roofs (above \(6:12\)) can cause dangerous, sudden snow avalanches, requiring the installation of snow retention guards.
- Warranty Compliance: Manufacturers specify strict minimum slope requirements. Installing a panel on a roof pitch lower than recommended will often void the material warranty.
ESSENTIAL CONSIDERATIONS FOR METAL ROOFING
Because metal roofing is incredibly smooth, water accelerates off the surface faster than it does on asphalt shingles. You may need to plan for oversized gutters to prevent runoff from overwhelming your drainage system. Additionally, proper underlayment and ventilation remain crucial to managing condensation and preventing moisture buildup in any metal roof system.
OVERLAPPING PANELS
“Panel side lap” refers to the overlap of two exposed-fastener metal panels. On lower roof slopes, water can enter the building’s seam through capillary action. Applying butyl seam sealant along the rib of the first panel before installing the second panel resolves this issue.
According to the International Building Code and most panel manufacturers, when using exposed-fastener panels on slopes between 1:12 and 3:12, it is recommended to apply sealant tape along the overlap. If a roof slope is 3:12 or greater, you can leave out the tape sealant at the overlap.
PANEL PROFILE
The panel’s profile must be taken into account. The minor and major ribs do create the aesthetic of an exposed fastener panel, but the height of the major ribs is not the most important factor; instead, the shape of the ribs on both sides of the panel is more important.
The minor bends in a metal roof are often called “anti-siphon channel,” which, in turn, form a barrier that prevents water from entering.
To some, these differences don’t seem big, but they are. These differences affect panel production and weather integrity. Therefore, we highly recommend using seam sealant for every roof installation, including top panels and quality panels, regardless of the slope. Note: if the slope is above 3:12, the slant isn’t vital for installation.
FASTENERS
If an exposed-fastener panel occurs, it means a screw pierced through the panel and substructure during installation. While they can offer more economical pricing than the standing seam system, they are limited to projects with specific required roof slopes.
Although the washer seals the fastener hole, improper installation or prolonged exposure to moisture can cause it to degrade, allowing water to enter the building. Therefore, exposed-fastener panels are not recommended for slopes with a slope ratio of less than 1:12.
We want to confirm that you have chosen the perfect panel for you and your roof slope and that it is installed properly. At Nu-worxs, we are certified GAF Master Elite Installers.