Getting an accurate measurement for your metal roofing panels may seem like a no-brainer, but it’s not quite as simple as length x width. The many complexities of a roof must be taken into consideration in order to ensure your numbers add up. For instance, anything that intrudes upon a roof plane needs to be included in drawings with labeled measurements as these conditions will all affect the measurement but are sometimes overlooked.
Let’s look at some specific conditions to consider before getting out the measuring tape as well as some handy tips for installers.
Building Conditions to Consider Before Measuring
The type of roof system
Is it going to be a standing seam roof system or an exposed fastener system? Once you’ve decided on your roof type, we recommend reviewing all of the conditions/details on the roof. If it’s a standing seam roof, will the roof system need to float? If so, where will it be pinned, and what direction will it float?
At MBCI, we have published installation technical manuals for installers and erectors to utilize in order to familiarize themselves with how to adjust for ridge conditions or end lap conditions, for instance.
Is it a new or existing metal building?
If it is an existing building, are there new or updated building codes to consider? This could possibly dictate panel type, gauge, or width, or require additional framing members that could impact the final measurements.
What is the purlin spacing?
The panel break at the purlin for an endlap condition will need to be considered.
Are there extensions, overhangs or penetrations?
Include any roof extensions or overhangs that may not be apparent at first glance. Any and all roof conditions should be considered when calculating panel and trim length, including any roof penetrations such as pipes, roof curbs, skylight hatches, etc.
The manufacturer’s details will aid in determining such things as panel hold back at the ridge, or panel overhang at the eave or gutter. Also, roof or slope transitions, and panel hems should be considered.
The thickness of the insulation could determine or dictate the fastener type used.
- Field verify the roof slope. The contractor should gather the field dimensions so measure when the framing is in place. While you can measure off of a set of plans, it’s not a definitive way to do things because things change in the field.
- The structure should be square while you’re measuring. Scaling from plans may get you close, but measuring erected framing that is plumb and square is the most accurate.
- You should measure multiple spots.
- It’s a good idea to use a plan view of the roof or sketch a bird’s eye view to record your measurements.
- Record your measurements in the units of measure that your manufacturer uses, typically feet and inches, to avoid errors.
- The erector may elect to add a few inches to the length of the panels at a hip or valley to remedy any cutting mishaps since these panels will be field cut to the hip or valley angle.
- Some contractors include one or two extra panels at the longest length for any errors or jobsite damage.
Ultimately, the takeaway is that any differential when measuring metal panels for installation could affect a building’s performance, so it’s important to keep all potential scenarios that could affect measurement accuracy in mind—throughout the entire process. To find out more about the proper way to measure a roof for metal buildings 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.