Inspection strategies designed to ensure roofing systems deliver bottom-line benefits to facilities

— By Kevin Ernster

Metal roofing systems on the market today have evolved into reliable and long-term systems. Their panels can be made out of galvanized steel, aluminum and copper, depending on the application that a commercial or institutional facility requires.

A properly installed metal system can provide many years of maintenance-free performance. But, as with other types of roofing systems, it is important to inspect metal roofs periodically to ensure they perform as desired in protecting buildings and their operations.

Maintenance and engineering managers who are developing and updating a roofing inspection strategy need to be aware that the inspection and maintenance of metal roof systems requires different techniques and materials than those associated with built-up or single-ply systems.

The next generation
The manufacturers of metal roofs have updated their products in recent years. Now, the use of advanced corrosion-resistant treatments such as Kynar finishes gives managers and specifiers a variety of color choices, and aluminum-galvanizing treatments provide metal systems with the ability to be used in a variety of environments.

Advanced installation and attachment techniques allow metal roof systems to be quickly and efficiently installed. Where seams were once handcrafted, they are now integrated into the panel as a self-locking seam, or a mechanical seamer seals them. Also, the use of sliding clips for attachment gives panels the ability to accommodate expansion forces without damage to the panel and to withstand substantial wind forces.

Finally, the advent of lightweight, sub-structural systems has opened the market for metal systems to be used as a retrofit option over existing low-slope roofs.

Inspection challenges
The first step in establishing a metal-roof inspection and maintenance program is to identify the type of system installed on a particular facility. Metal roof systems fit into one of two broad categories.

Architectural systems are classified as water shedders because their seams are not rollformed, as is the case with structural panels. Architectural systems usually consist of flat panels that snap together or use a cover strip at the seams to join the panels.

Typically, they are installed on steeper slopes with shorter panel lengths than structural panels, and due to their flat design, they have minimal load-carrying capacity. Because of this minimal capacity, they are installed over another substrate, such as plywood.

Structural systems have load-carrying capacities and do not require a substrate for support. The system’s structural capacity is built into panels through the use of trapezoidal breaks placed in the metal pans at the seams. Panel seaming is accomplished by rollforming the seams or lapping the panels and installing a fastener through the panel.

Structural systems usually are attached by concealed clips that are secured to the substrate and hook over the panel. The clips float freely, allowing panels to move through expansion and contraction without restraint.

The inspection process for metal systems is similar to that for other roofing systems. The inspector should conduct a walkover of the roof to identify drainage characteristics, as well as deficiencies in the field and around projections. These inspections should be performed at least once a year and after major weather changes. On structural systems, they must be sure to walk over the underlying purlins to check for panel deflection.

Deficiencies to inspect for in metal systems are different than those in other roofing systems. Items that should be inspected include panel corrosion, loose fasteners at panel laps, and seriously deflected panels.

At all fastener locations, particularly older seam-fastened systems, the deterioration of neoprene washers that seal the fasteners to the panel is common. More difficult to detect but also common on older systems is the elongation of the fastener hole. After years of expansion and contraction, the hole where the fastener penetrates the panel can become larger than the washer. Inspectors might need to remove fasteners to verify the condition.

If roof inspectors believe there are leaks from panel end laps, they should make sure sealant is present and that it is located in front of the fastener, not behind it. They also should note if the sealant is cracked or dried.

Inspections also should include a check of panel terminations at the eaves, ridges and valleys to ensure that closure strips are in place. These strips are made of foam or rubber, and they fit under the panel to keep weather and animals out of the roof. Inspectors should look at trim pieces at the rakes to ensure they are properly sealed and fastened. At the laps of the panels, they should check for buckling or standing water, which indicates unusual movement within the system.

As inspectors walk over roofs, they should check penetrations, where most leaks occur, and verify that the sealant is soft and pliable where the field and flashing meet. Fasteners should be tight, and the neoprene washers should be in good shape, not cracked or dried.

Metal systems typically are installed on a slope, so drainage rarely is a concern, but they usually are drained by using gutters, either exposed or concealed. The inspection process also should include looking into gutters and downspouts to make sure they are clear of debris and restrictions.

If the roof’s slope is very shallow, the inspector should look for ponding or restricted drainage in the roof field. Panel deflection can sometimes cause dips in the field which trap water.

To make the most of time invested in surveying roofs, inspectors should carry along a socket wrench that is the same size as the panel fasteners. By doing so, they can remove fasteners for inspection and tighten loose fasteners. It is also helpful to use a roof plan in carrying out the inspection to identify the location of deficiencies. If repairs are required, such a plan makes it easier for the person making the repairs to find them.

Making repairs
When repairing a metal roof, workers should never use asphaltic-based roof cement because it can become hard and brittle and unable to accommodate movement found in metal systems. Once this material is used, it is very difficult to remove and replace with an appropriate material.

For small areas of corrosion, workers should sand the panel lightly, apply a rust-inhibiting primer and coat with a Kynar-based finish to match.

On larger areas of corrosion, crews might need to apply an elastomeric coating formulated for use on metal roof systems. For perforated panels, depending on the type of system, they might need to replace the panel. If the system is a structural standing-seam panel, replacement is difficult. Depending on the amount of perforation, crews might need to overlay the panel or coat it with reinforcing mesh and liquid coating. Seriously deflected panels should be replaced if they are creating ponding water.

Deterioration of neoprene washers requires removing the fastener and replacing the washer. If the fastener hole is elongated, replace it with an oversized fastener and washer.

All sealant used on metal systems should be a high-quality butyl-based caulk. If there is extensive repair required for the fasteners or panel laps, managers or repair crews should consult with a metal-roof-coating supplier on the use of coatings over troubled areas.

Penetration repairs are similar to field repairs: replace deteriorated sealant, washers and fasteners as required. If deterioration is extensive, workers might need to use a liquid-applied coating. Drainage problems can either be very easy to correct, such as cleaning a gutter&Mac226; or very difficult, as in the case of a large area of deflected panels where sections of the roof require replacement to correct.

Metal roof systems are designed and installed to deliver long performance life. By including these systems in a comprehensive roofing management strategy —including regular inspections and the use of recommended repair procedures and materials — managers can help their organizations reap the bottom-line rewards promised by metal roofing systems.

Kevin Ernster is a registered roof consultant and vice president with Benchmark Inc., a national roof consulting firm based in Cedar Rapids, Iowa.