Metal Roof Pitch Part II: Panel Selection for Your Building End-Use

In part one of our series on metal panel roof pitch, we looked at the engineering and strength considerations that need to be taken into account when designing or specifying a building. In part two, we’ll review how to make the right metal panel selection for your building end-use by looking at the building type and roof pitch to find the optimal combination of form and function.

Types of roof panels:

Different types of metal roof panels are better suited for certain roof pitches and this mostly has to do with panel rib height and how they’re seamed together. For instance, the lower the pitch, the taller the rib of the roof panel needs to be in order to optimize water carrying capacity. Also, the lower the pitch, the slower water runs off the roof; combined with wind pressure, this can hold water at the eave. As an example:

  • On 2:12 and lower pitches for commercial/industrial jobs, weathertightness warranties will use a mechanically seamed panel because it creates an impenetrable lock that keep water from seeping between the panels. Seamed panels can be thought of as more hydrostatic (resistant to water), whereas non-seamed panels are hydrokinetic, i.e., water runs off of them, but they are not designed to be a water barrier.

Building Type and Use:

Whether residential, post-frame or commercial, structures follow general design criteria regarding metal roof slope, based on to the building type and use. For instance:

Gabled v. Hipped: gabled roofs provide more interior headroom while with hipped roofs, endwall sheet height can be reduced, making for easier ordering and installation as you don’t have to cut/miter the sheets.

  • Residential v. Post-Frame and Commercial Use: While it can generally be assumed that thicker-gauge panels are stronger, the type of building construction, location and end-use can affect the choice in panel thickness. Residential roofs generally have steeper slopes (often due to aesthetic sensibilities), while commercial and post-frame buildings will typically have a shallower pitch to increase the strength of the building. Buildings such as pole barns, post-frame buildings, warehouses and garages can require roof panels to span longer distances between supporting trusses and purlins and therefore require thicker panels to ensure the roof is structurally sound and can aid in reducing the chance of collapse under the weight of snow and water—particularly when the roof pitch is low. For smaller buildings—like residences—with supporting trusses and purlins that are typically closer together, thinner panels can be used in conjunction with thicker trim for an economic, structurally ideal residential metal roofing system. See our blog on metal panel gauges for more.
  • Economics: When a roof has a shallower pitch, less material is needed to cover the same roof span. This can be more economical since fewer square feet of material needs to be purchased, or at least help in offsetting the cost of the thicker panels commonly used on low-slope roof—a consideration often important to companies with multiple properties. Likewise, while more material may need to be purchased for a high-sloped roof, you may be able to buy thinner, less expensive panels since high-slope roofs don’t typically need to be able to support heavier loads like low-slope roofs do.
  • Aesthetics: Traditional residences typically feature a higher roof pitch while this may be less important to commercial building owners. However—from a functional standpoint—thicker panels can be more forgiving of installation errors such as over-tightened screws and aren’t as likely to transfer waves and bumps in sheathing.

Solar Panels and Roof Pitch:

The geographic location of a structure will determine the angle at which the solar panels should be installed. Generally. the closer to the equator you get, the lower the slope the solar panels can tolerate as roofs closer to the equator have more consistent exposure to sunlight as compared to those farther away. If you plan to add solar panels to your metal roof, be sure to check the Solar Reflective Index (SRI) values and minimum slopes set by the ASTM and local governing codes. These standards will advise adequate slope based on your location as well as help control things such as heat island effects, etc.  For more information on solar reflectance and how it is affected by the color of your metal roof panels, see our blog post on cool metal roofs.

Conclusion:

Roof slope is a factor that affects many decisions when it comes to any metal building roofing project regardless of the building’s end use. When embarking on any metal roofing project, be sure that the panels you’ve selected meet local building codes and are produced by a quality manufacturer with knowledge and experience designing for different applications to ensure you get exactly what you’re looking for. For more information on metal panel selection for your building end-use and to learn more about recommendations on roof slope for different building types, contact your local ABC representative today.

 Additional Resources:

For more information on slope requirements, visit NRCA’s website. For more information on steep-slope metal roofs and their benefits, visit the Metal Construction Association’s website.

Metal Roofing Gauges: What Are The Best Gauges For Metal Roofs?

When your customers decide to use metal panels for their building project, they’ll need to make several decisions to choose the best panel. One of the first decisions they’ll make is what gauge or thickness they need. There are a variety of metal roof and wall panel profiles to choose from, and they are all available in several gauge thicknesses … but what does that really mean to your customers and how does that affect your business?

Metal Panel Gauges: Are you getting what you pay for?

Metal Panel Gauges Deciphered

U.S. manufacturers express the thickness of metal panels as their ‘gauge’, with 22-gauge being the thickest and 29-gauge the thinnest of traditionally-sold metal roof and wall panels. Each gauge represents a nominal decimal range. For example, a 26-gauge steel panel can range between 0.0179 and 0.0217 inches thick according to a University of North Carolina at Chapel Hill resource.

This means that while a 26-gauge panel from one manufacturer could measure 0.027 in. thick, a 26-gauge panel from another manufacturer could measure only 0.0179 in., but both are sold as 26-gauge panels. Although those seem like small numbers, they represent a noticeable difference in panel stiffness and strength.

So how do you and your customers know if the metal panel manufacturer has used thinner sheeting and made up the difference with a coat of paint? When ordering inventory, you should look beyond the gauge number to the manufacturer’s specifications on metal thickness. This will give you peace of mind that you’re providing your customers with the gauge they’re paying for and the quality they need to get the job done.

 

Costs of 26-Gauge Panels vs. 29-Gauge Panels

Expect to pay more for thicker panels. The cost of a 26-gauge product will be about 15 percent higher than a 29-gauge with the same profile from the same manufacturer. While some people insist that the extra cost is always worth it, that may be misleading. Yes, thicker panels are stronger, but the importance of that added strength depends on the type of building construction as well as the customer’s priorities and location.

 

When To Choose a Thicker Metal Roofing Gauge

There are instances where thicker gauges always earn their keep. The most common of these is the post-frame building, or pole barn: an open-framed structure used for barns, garages and warehouses. Post-frames generally lack structural sheathing, so the roof and wall panels must span between the supporting trusses or purlins. Because 22-, 24- or 26-gauge sheeting is thicker, and will, therefore, remain more structurally sound over a longer span than a 29-gauge, the building needs fewer supports, which saves your customers money. For post-frame structures like this, it is important for your customers to consider the potential snow load the roof may need to support when choosing the metal panel gauge. Lighter-gauge (thicker) panels may save your customers from structural collapse in the winter months!

Lighter gauge (thicker) metal is also more forgiving of installation errors such as the over-tightening of screws, and it won’t be as likely to transfer bumps and waves in the sheathing. (The latter is more likely when re-paneling an older home.) Thicker trim pieces will also lay more accurately, so some homeowners and contractors opt for 29-gauge roof and wall panels with 26-gauge trim, a combination that is common and cost-effective.

 

When To Choose a Thinner Metal Roofing Gauge

Span isn’t always a concern in the residential market. Nearly all homes have a layer of plywood or oriented strand board sheathing covered by a weather-resistant barrier. The metal panels are affixed to the sheathing and serve no structural role in these instances; their job is to keep the sheathing dry. A quality 29-gauge panel is more than adequate for this—which is why it’s used on nearly 80 percent of homes with metal panels.

Despite this, thicker (lighter-gauge) panels can make sense for buildings in hail-prone areas, but not because of structural integrity. A 29-gauge metal panel can have the same impact-resistance rating from Underwriters’ Laboratory (UL) as a 26-gauge panel; the advantage of thicker metal panels in this case is that they are less prone to denting. If your customer lives in a place like Cheyenne, Wyoming (the hail capital of North America) and is concerned about long-term appearance, thicker panels may be the better option.

 

Let ABC Help You Choose the Right Metal Panel Gauge!

For more information about metal panel gauges, check out our panel selection chart or contact your local ABC representative today. Additionally, use our online ordering tool to find accurate pricing, create quotes and place orders for metal building products anytime, anywhere and from any device.  If you don’t already have an account, register for access today!

DISTRIBUTORS: Shop online at shop.abcmetalroofing.com!