Corrugated metal roof panels, commonly used on agricultural, storage and similar buildings, share many of the same characteristics as structural standing seam roof systems, but some properties make them more vulnerable to nature’s impact.
Differences Between Standing Seam and Corrugated Metal Roof Systems
- Corrugated panels are made from thinner metal (typically 26-28-gauge) than standing seam panels (24 gauge). Because they are made from thinner metal, they are less resistant to damage from impact and from expansion and contraction due to daily and seasonal temperature changes.
- Corrugated panels are typically made in standard sizes, not rolled-to-length as can be done with standing seam panels. More panels are needed to cover the roof, resulting in more seams, more fasteners, and more potential leak points. The fixed length results in panels typically being trimmed to fit the installation. On site cutting of metal can lead to corrosion or rusting due to paint damage.
- Standing seam roofs are installed with fasteners and clips under the roof panels to hold them in place. The concealed fastening system is designed to allow some panel movement, resulting in less stress to the metal roof. Corrugated panels are installed with screws or nails that penetrate the panel and are firmly secured to the wood or metal structure. A rubber grommet on the fastener is provided to prevent water penetration around the fastener. The nails or screws are rigid, causing the metal to gradually wear around the fastener as the metal moves due to thermal expansion and contraction. As time passes grommets weather and crack, allowing water penetration around the fastener that will rot a wood structure or rust out structural purlins in a metal building. Due to corrosion and movement fasteners can loosen or back out, also causing leaks.
- Installation of fasteners for a corrugated metal building is an exacting task. The nail or screw must be driven straight (perpendicular) to the metal panel and driven to exactly the right depth to properly seat and compress the grommet. An improperly installed fastener will not be watertight and will allow water penetration from the day it was installed.
- Thin, corrugated roofing panels are more prone to damage from hail, foot traffic, work on the roof, windblown debris or other impact. Stepping on ribs rather than carefully walking only on the center panels can crack the metal, causing leaks.
Addressing Corrugated Metal Roof Problems
As with standing seam roofing systems, there are several options for repairing or reroofing a corrugated metal panel roof. These include:
- Sealing, coating, spray-on foam: These low-cost options seal the rooftop and add a waterproof coating, but they are only temporary fixes because weather variations will continue to affect the roof deck and fasteners.
- Replacement with a new metal roof: The corrugated roof was part of the original building package and it may seem appropriate to replace it with the same type of system. But the failures being faced now will again develop over time. Another consideration is the installation of a replacement metal roof will disrupt building operations, open the facility to weather and pose a hazard to staff and building contents beneath as panels are removed and replaced.
The Perfect Solution: A Duro-Last Membrane Retrofit Installation
A membrane retrofit for corrugated roofs, manufactured by Duro-Last and installed by Sentry is clean, quick, cost effective, and non-disruptive.
We place insulation between the metal ribs to create a level surface, then overlay that with high-density cover board or another layer of insulation to provide a uniform, flat surface across the rooftop. The Duro-Last PVC membrane is rolled out over the insulation and mechanically attached to the building structure below.
All roof penetrations, such as exhaust vents, pipes or stacks are flashed with custom-made prefabricated Duro-Last components to save labor costs and ensure a top quality, long-lasting installation.
We also include roof edge details that will provide secure wind resistance and an excellent finished exterior appearance. This single-ply retrofit system results in long-term, warranted watertight protection, more insulation, and depending on the building use, energy savings.
Warranty terms of up to 30 years and hail warranties will be provided by the roof system manufacturer, Duro-Last.
Advantages of the Duro-Last / Sentry Retrofit System
- Because we install it over the existing roof without removal of the metal, there is no disruption to your building operations or risk to building contents and staff.
- The installation includes additional insulation, improving building energy efficiency and helping eliminate winter moisture condensation on the underside of the roof.
- The Duro-Last membrane is highly reflective, improving the building’s energy efficiency and helping keep it cooler on hot, sunny days. The result is a more comfortable working environment and improved productivity.
- The addition of solar tube skylights is easily accomplished during the roofing project and can save lighting costs and improve worker comfort and productivity.
- The membrane system is not affected by expansion and contraction of the original metal roof, providing an excellent service life.
- Duro-Last provides several warranty options to allow you the level of security you prefer. The Duro-Last warranty is simple, comprehensive and in our opinion, the best in the industry.
Sentry Roofing, Inc. is one of the largest, most experienced Duro-Last contractors in the nation. We have 35 years’ experience installing Duro-Last, with satisfied customers across 40 states.
We complete numerous metal retrofit projects every year of all sizes; our largest project to date was for a single warehouse roof of over one million square feet.
At Sentry, your concerns and needs come first. We would consider it a privilege to meet with you to discuss any roofing needs you may have!
