Roofing Problem Areas

Flat roofs are prone to ponding water.

Flat roofs are prone to ponding water.

Facilities maintenance issues can have a major impact on productivity in industrial and commercial environments with something as small as a leaking roof causing significant disruption and downtime. Years of experience suggest that 90 percent of the problems we are presented with today will arise from a mere 10 percent of the roof’s total area. But are some roof types and roof areas more susceptible to damage than others? Moreover, how do these roofing problems arise and how can they be categorized?

Flat Roofs

Flat roofs are commonly chosen for industrial and commercial buildings, covering the vast majority of offices, factories and warehouses around the globe. However, despite their popularity, my firm’s experience indicates that the bulk of roofing applications owe to the failings of flat roofs. This begs the question; do the benefits of flat roofs outweigh the disadvantages?

Currently, the flat roofing market is in a particularly healthy state. It is easy to see why because flat roofs do in fact offer a great deal of advantages. Notably, they are a low-cost option for many projects, being easier and more economical to install, inspect and maintain. Therefore, they prove highly popular with many commercial facilities and industrial buildings.

However, flat roofs are historically problematic, suffering from an array of issues commonly arising from standing water and traditional roofing materials. Pooling of water on roofs can be attributed to inadequate roofing materials or, strangely, a roof being “too flat”. Flat roofs should actually feature a small gradient to allow sufficient rainwater run-off; otherwise, the weight of water pooling can lead to deflection and numerous subsequent issues.

Roof flashings can prove problematic due to dissimilar materials.

Roof flashings can prove problematic due to dissimilar materials.

Of course, other roof variations, such as pitched or slanted roofs, will offer their own range of complications; however, complications with pooling water are not among these. This distinct disadvantage is one of several that can lead to serious problems within that troublesome 10 percent. The most common problems can be split into three separate categories.

Dissimilar Materials
Most roofs form a veritable patchwork of materials, including anything from glass and plastics to masonry and metals. Industrial roofs can be particularly troublesome as they boast a multitude of pipes, heating units and other protrusions that make the roof geometry complex to cover effectively. Whatever the combination of roofing materials is, ensuring long-term adhesion and sealing between all these dissimilar materials is crucial—and can prove problematic.

Flashings fall into this category and are a common fixture of flat and pitched roofs, where metal, brick and felt or bitumen can often all meet. Exposed to varying temperatures and weather conditions, these materials can act differently, altering shape and size dependent upon that material’s characteristics. This can result in roofing weakness due to different expansion and contraction rates of the materials, allowing for water ingress through developing gaps. Moreover, this category includes areas where two metals may meet. Dissimilar metals exposed to continuous weathering can potentially lead to galvanic corrosion, which deteriorates the roof’s protection, loosening the materials and once again leading to issues like leaking.

Joints and Seams
Joints and seams spell considerable trouble for many roofs, predominantly due to the effects of movement. All buildings will feature a degree of movement as a result of thermal expansion, contraction and wind, making joints and seams one of the most vulnerable areas. Resulting gaps or lips can be created, increased further by wind uplift, which may allow water ingress or exposure of unprotected materials to corrosion and weathering.

Seams around skylights and roof protrusions can cause roof vulnerabilities.

Seams around skylights and roof protrusions can cause roof vulnerabilities.

Found whenever two materials meet, joints and seams are a common sight on industrial roofs and one that occurs frequently on roofs covered using traditional materials. For instance, felt or bitumen surfaces are layered in strips and require heat to fuse them together and create one barrier of protection. However, continuous exposure to the elements can lead to delamination of the roofing material, creating areas of vulnerability, such as lips.

Similarly, parapet walls can also become vulnerable at the joints, normally caused by movement between the brickwork. This can develop through movement in the building or perhaps vegetation forcing through the joint, widening any gaps further and causing moisture ingress. Furthermore, this problem is shared by the seams around skylights and glazing bars, which degrade over time due to the dissimilar materials present and associated movement.

Unlike other problem areas in this category, cut-edge corrosion does not stem from two materials meeting. In fact, it falls into this category as it is an uncoated seam of metal that, left exposed, will corrode and result in the damage spreading as the metal is slowly eaten away. Corrugated metal roofs are susceptible as they are cut and the edges never receive protection, meaning when cut-edge corrosion begins, it is important to treat it as soon as possible. In certain instances, roof sheets need to be removed and replaced, which is extremely expensive.

Metals seams are often neglected and can develop cut-edge corrosion

Metals seams are often neglected and can develop cut-edge corrosion.

Other Forms of Damage
Lastly, roofs are susceptible to various forms of damage in the immediate and long term. Long-term damage will generally arise if roofing is left unmaintained, to suffer from aging and neglect. A key example of this type of damage involves single-ply roof coverings. Over time, rubber roofing materials are subjected to the environment and constant UV exposure. Once again, over this period the material expands and contracts, becoming brittle and losing its former flexibility, making it prone to cracking.

In addition to weathering, wildlife can have a detrimental effect on roofing materials, as bird litter can chemically attack the plastic coating on some roofing systems. High levels can cause damage and subsequent deterioration of the lining, which can potentially lead to leaks or exposure of metal to corrosion.

With regard to immediate damage, working on roofs is also a common way in which damage can occur. As highlighted before, one of the key selling points of flat roofs is the ability to carry out maintenance and inspection easily. Whether it derives from maintenance or rooftop developments, such as HVAC installation, extensions or rooftop fire escapes, the foot traffic over flat roofs can lead to immediate damage of the roofing substrate, through piercing and general wear.

Over time, rubber roofing materials can become brittle and crack

Over time, rubber roofing materials can become brittle and crack.

Eliminating the Troublesome 10 Percent

For the majority of these problems, it is possible to find a repair solution. However, when left without treatment, the roof can become too damaged to refurbish, leaving costly replacement as the only option. Repair methods have evolved significantly over the years and eliminating the troublesome 10 percent is becoming far easier to do since the advent of liquid and cold-applied technologies. Not only does this signify a breaking of tradition, but crucially highlights the evolution of roofing maintenance materials.

PHOTOS: Belzona

Zinc Head Screws Resist Corrosion

Triangle Fastener Corp.</a> has launched a complete line of corrosion-resistant zinc head screws.

Triangle Fastener Corp. has launched a complete line of corrosion-resistant zinc head screws.

Triangle Fastener Corp. has launched a complete line of corrosion-resistant zinc head screws. Available on the high-performance BLAZER Drill Screws, these fasteners are preferred for use in many warranted roof systems. The ZAMAC-5 Zinc Alloy Head provides superior strength and will not red rust. The carbon steel shank is TRI-SEAL 1,000-hours salt-spray- coated, which increases the corrosion resistance by more than 20 times compared to zinc-plated screws. An EPDM washer seals and weathers. Sizes include #12 and 1/4-inch diameters in BLAZER-3 and BLAZER-5 drill points in lengths up to 4 inches.

MCA Publishes Technical Resource on Selecting Proper Types of Fasteners

The Metal Construction Association (MCA) has published a new technical resource to assist designers and installers in selecting the proper type of fastener: Fastener Compatibility with Profiled Metal Roof and Wall Panels.

Found in the technical resources section of the MCA website at www.metalconstruction.org, the new bulletin includes a convenient table that serves as a guideline to check fastener compatibility with different types of cladding materials. The table references corrosion resistance between eight common types of metal roof and wall cladding materials and nine different fasteners. With it, users can quickly determine if they are matching the right fastener with the right roof or wall material to ensure performance over time and a strong, weather tight attachment.

The integrity and aesthetics of a building is at risk when the wrong type of fastener is used with a metal roof or wall cladding system. Premature corrosion of the metal panel and/or the fastener may occur under certain conditions. Known as galvanic corrosion, this is often a result of corrosion between the dissimilar metals that are in contact with each other. To prevent dissimilar metal corrosion at the connection point, fasteners should be made of a compatible or the same material as the roof or wall material whenever possible. At the very least, the fastener should display equivalent corrosion resistance to the material being fastened.

The bulletin also provides a discussion on the fastener durability and the roles (primary or secondary) and type (self-drilling, self-tapping and self-piercing) of fasteners that will help designers and installers achieve high fastener performance.

The MCA updates its education/technical resources section on its website on a regular basis, addressing practical and educational topics related to the metal construction industry. All materials are available free to website visitors to download in PDF format.

A Metal Roof Crowns a Residential New-construction Project

When Charles Callaghan purchased the two vacant lots next to his home in Ponte Vedra Beach, Fla., he thought they would form the perfect location for his family’s dream home. A team comprised of architects, contractors and manufacturers worked together to bring his ideas to life in the form of a new 7,500-square-foot residence. The building’s crowning feature is a metal roof system that was designed to complement the aesthetics of the home and stand up to the harsh oceanfront environment for decades to come.

The roof of the Callaghan residence in Ponte Vedra Beach, Fla., features 12,000 square feet of Petersen Aluminum’s Snap-Clad in Slate Gray.

The roof of the Callaghan
residence in Ponte Vedra
Beach, Fla., features 12,000 square feet of Petersen Aluminum’s Snap-Clad in Slate Gray.

“With the larger lot, we thought we could do something unique to the neighborhood,” Callaghan says. “When we first met with the architect, there were a few keys we wanted to stress. First, we didn’t want a boxy-looking house. We also wanted shingle-style siding and a metal roof. We like the look of the metal roof, we like the durability, and we thought it would be a good way of complementing the shingles on the house.”

At every phase of the project, the team of construction professionals ensured the project was executed with precision, down to the last detail of the metal roof.

THE DESIGN

The house was designed by Jaycox Architects & Associates, Jacksonville, Fla. According to William R. Jaycox, principal, the plan made the backyard pool the home’s focal point. “They wanted to do a casual, shingle-style beach house that wasn’t like everyone else’s house,” Jaycox notes. “We designed the house so it was mostly single-story and spread it out around the pool, which made for an interesting roof design. It’s all in small modules.”

The L-shaped home features a master-bedroom suite on one side while the other side contains the living room, dining room, kitchen, family room and guest bedroom. “This one also has a four-car garage under the main roof, and, because the house wraps continuously around the pool, you get a fun little foyer in the front with a little cupola up above, you get the dormers for the bedrooms in the attic, and the master suite is a little pod unto itself,” Jaycox adds. “The back has a pool pavilion separate from the house. When you put all of those elements together, you get a very interesting structure, and the metal roof was perfect because it accentuates the lines.”

The roof system specified included 12,000 square feet of aluminum panels in the cool-color Slate Gray. “This house is only a few blocks from the ocean, and in those cases we typically use aluminum,” Jaycox says. “We’ve had great success with that system. It’s absolutely bombproof from a corrosion standpoint with stainless fasteners, heavy-gauge aluminum and the Kynar finish.”

Thorne Metal Systems installed a high-temperature, self-adhered underlayment beneath the metal roof, as specified.

Thorne Metal Systems installed a high-temperature, self-adhered underlayment beneath the metal roof, as specified.

When applied by a certified installer, the system can qualify for a 20-year Oceanfront Finish Warranty from the manufacturer. In addition, the roof meets all Florida’s tough building-code requirements. The system, consisting of 0.040-gauge aluminum, 16-inch-wide panels with fastening clips spaced at 24-inches on-center, carries a Miami-Dade NOA with a -110 PSF uplift. (The UL 90 uplift is -52.5 PSF.)

THE INSTALLATION

The roofing contractor on the project was Thorne Metal Systems of Middleburg, Fla. Owner Bill Thorne has been installing metal roofs since 1989. He formed his own company 13 years ago, and it has become the go-to metal roof installer for Jaycox Architects
& Associates and the general contractor on the project, C.F. Knight Inc., Jacksonville.

Thorne has a lot of experience installing this particular aluminum roof system. “The system is a very easy system to install,” he says. “It’s very user- friendly. The panels have male and female joints that snap together and are held in place with stainless-steel clips.”

PHOTOS: Petersen Aluminum Corp.

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Aluminum Stands Up to Coastal Environments

Union Corrugating has launched a new aluminum roofing line that is geared toward high-end applications, including the coastal environment where corrosion resistance is critical.

Union Corrugating has launched a new aluminum roofing line that is geared toward high-end applications, including the coastal environment where corrosion resistance is critical.


Union Corrugating has launched a new aluminum roofing line that is geared toward high-end applications, including the coastal environment where corrosion resistance is critical. The new product was created in response to customer demand. The product line, which uses corrosion-resistant, prime-quality 0.032-inch aluminum, is available in six profiles and 29 Kynar500- or Hylar 5000-based finish colors. Weather tightness and coastal saltwater warranties are available.