Most metal roofing system installers know the importance of keeping panels on module, i.e., holding the width of the panel. But holding module alone isn’t enough; keeping panels square is equally important as the two go hand in hand. When proper attention is paid to both, you will have a faster install—ensuring longevity and functionality of the roof system so that it will be able to properly expand and contract as designed—not to mention improved appearance.

The ability to hold panel modularity is directly dependent upon several factors, including:

• Skillset of the installer
• Frequency that modularity is checked
• Substrate deficiencies
• Insulation system
• Appropriate methods being used to hold panel modularity during panel installation
• Keeping symmetry/maintaining squareness

Here are some important considerations for ensuring success for panel alignment.

The Relationship Between Holding Module and Squareness

The roof panel is not going to “hold itself” 100% on module and square by installing just as received using only the hardware components supplied from the manufacturer. It is the installer’s responsibility to ensure the proper alignment and squareness of the panel install in order to hold panel module. For example, if you’re working with a 16-inch panel, installers need to keep the spacing of the panel ribs at 16 inches. In this way, the panel doesn’t become stretched or compressed. So, holding module is key along with holding square; the two are connected. If an installer doesn’t start the building out square, it will make it even harder to keep module with regards to the alignment of the panel.

As far as the overall appearance and performance, the success of the metal roof is going to be heavily dependent on how square it is installed and an ability to maintain proper modularity. There are a number of suggested methods for doing so outlined below. Installers must decide which method works best for their them and their roof panel application.

Methods to Ensure Success

The key method is measuring ahead and monitoring your installation so you know where you should be along that roof install. The metal panel is typically 24-gauge or 26-gauge material and therefore it’s easy enough to pull it ahead or have it become crowded during installation if you’re not staying close to your marks, and therefore it’s easy to get the panel out of module. The bigger impact, aside from just aesthetics of being on or off module is the performance of the system itself, to where it could become under stress or it could go through extra deformation due to being out of module and out of square. Its important to verify/measure the panels leading edge and adjust as needed via roof clips or other panel hardware. Some suggested methods include:

• Run a string line from eave to ridge square to the eave and measure from the string back to each panel run. The string line is moved ahead as the roof installation progresses. If installing over solid substrate, snap chalk lines for alignment points along the roof.
• Use a metal measuring tape permanently secured to the substrate at panel endlap locations, ridge and other intermediate points for permanent reference to check module.
• Mark the eave line for every rib installation to ensure the panel stays on module. Trapezoid panels offer metal closures for proper placement at the eaves to assist in holding module while vertical rib panels do not.
• Pre-drill substrates at the endlaps and ridge locations for clip alignment ahead of roof panel installation. A hole can be located at the leading edge of clip location so that an awl or punch can be inserted into the hold to align the clip and adjust accordingly. The holes drilled ahead of the panel at the corresponding panel module.

To assist with holding the panels’ shape when checking modularity, utilize outside panel closures or cut wood blocking to the panel’s correct width and insert between panel ribs. Note that a bad roof substrate that is out of tolerance for “flatness” will not be hidden or magically corrected by the panel installation. The alignment and tolerance of the substructure are equally critical to the panels’ squareness and being able to hold module. Substrate should be should be installed to a level plane tolerance that is no more than ¼” in 20-ft or 3/8” in 40-ft variance.

Do not stand in panel and/or keep as much weight as possible out of panel while installing clips. Not only is it unsafe but it changes the width of the panel and thus impacts modularity.

Use the correct combination of roof clip heights, insulation thickness and thermal spacers to maintain level panel installation and prevent panels from gaining or losing module. MBCI provides recommendations in its installation manuals regarding most common types of insulation thickness and means of attachment to various substrates. Additionally of note:

• Trimming of insulation or adjusting thermal block thickness can help control/modify panel modularity as needed.
• Alignment straps for trapezoid panels can be purchased from the manufacturer and installed on top of purlins before insulation. These set the clip spacing at 2-0” o.c and can be utilized at the endlap and ridge locations minimum or added at other locations.

At MBCI, we recommend that installers check module/square every three to four panels. If the panel grows or shrinks 1/8th of an inch or 3/16th of an inch with three or four panels or shows signs of being out of square, there’s time to recover from it by making adjustments to correct. If an installer just blindly puts the roof on for 50 feet or so and then realize they’re off module or out of square, it will likely be past the point of return to hold module and keep square.

For more information on installing metal roof panels to hold module, see our previous blog post on the topic.

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