Conductive Primer Designed for Electronic Testing of Conventional Roof Assemblies

Detec Systems has developed TruGround, a conductive primer which enables accurate electronic leak detection (ELD) testing on conventional roof membranes including black EPDM, TPO, PVC, modified bitumen, hot and cold fluid applied. According to the manufacturer, TruGround must be installed directly below the membrane per ASTM D7877. TruGround can be used for quality assurance testing on newly installed membranes and is chemically compatible with fully adhered, mechanically attached and torch-down membranes. Once applied, ELD testing can be performed for the life of the roof. Future breaches or seam voids can be quickly pinpointed, allowing repairs to be done immediately, preventing costly moisture damage from occurring.

For more information, visit www.detecsystems.com.

Industrial Maintenance Coating Designed for TPO and PVC Roofing Systems

EverprimeEverest Systems offers Everprime All Ply, a primer for various new and aged single-ply membranes. According to the manufacturer, this high-quality, plasticizer free, single component, solvent based primer can be applied by a spray brush or a roller. The product is designed to provide exceptional adhesion to new and aged TPO and PVC membranes. In addition, this high-performance coating provides excellent surface for subsequent application of acrylic, 100 percent solids Silicone and fluoropolymer coatings.

For more information, visit http://everestsystemsco.com.

New Roof Provides Security at Senior Living Complex

Photo: Johns Mansville

The Preserve At Palm-Aire is a landmark senior living community in Pompano Beach situated on 13 acres of lush, beautiful grounds in South Florida. Offering both independent living and assisted living programs, the health care facility’s primary focus is on preserving residents’ quality of life in every way possible.

The independent senior lifestyle at The Preserve At Palm-Aire is all about maintenance-free living, and that philosophy influenced the choice of a new roofing system for the facility.

The re-roofing of The Preserve At Palm-Aire was complicated by Mansard-style roofs and 5-foot to 6-foot high parapet walls that greatly restricted access to the existing roofing system, which was installed on a lightweight structural concrete deck. The use of trash chutes was impossible, so a large crane and dumpster were used to remove the roofing debris.

“What concerned us most was using such a large crane around an immaculately landscaped property fully occupied by tenants especially sensitive to excess noise and vibration,” says Geo Madruga, commercial project coordinator for A-1 Property Services Inc., the Miami-based roofing contractor on the project. Another important concern was that the low-slope roof had numerous penetrations, including those for 30 large HVAC units and various pipes and stack vents.

Finding a Solution

A-1 Property Services Inc. competed with several other contractors on an open spec bid. With the help of JM Sales Representative Lewis Buckner, A-1 advised the property owner that a 60-mil fleece-backed PVC membrane with DuPont Elvaloy KEE would provide the longevity, energy efficiency and chemical resistance required for the project. “We really pushed the PVC fleece backed as the superior roofing system and a unique solution for this building,” says Madruga. “We also felt more comfortable with JM’s PVC membrane due to our long track record with the product.”

Adhered directly to the concrete deck with a water-based adhesive, the fleece-backed PVC exceeded Broward County’s 175-mph wind resistance requirement. The PVC membrane’s high reflectivity also earned an energy efficiency rebate from Florida Power & Light Company. The product was also easy to install, depite the numerous penetrations, notes Madruga. “While there were definitely many unique penetrations, our 10-man crew had no problems with the heat-weldable PVC membrane,” he says.

Madruga’s concerns — and his company’s name — both reflect A-1’s desire to create long-term relationships with clients that include expert maintenance services. “We met the expectations of the owner’s roof consultant, but with offices in Washington D.C., the client placed a tremendous amount of trust in the roofing manufacturer and contractor,” adds Madruga. “We are specialists, and we don’t just walk away from any roofs that we install.”

TEAM

Building Representative: CRP Preserve Palm-Aire LLC, Washington, D.C.
Roofing Contractor: A-1 Property Services Inc., Miami, Florida

MATERIALS

Roofing System: 60-mil Fully Adhered Fleece-Backed PVC, Johns Manville, www.JM.com

Building to Last With Asphalt-Based Roofing

The property owner of this building opted for a BUR/modified-bitumen hybrid system with reflective white coating. Photos: Johns Manville

The advantages of a built-up roofing (BUR), modified bitumen, or hybrid roofing assembly include long life, a variety of maintenance options, and outstanding puncture resistance. This durability means property owners will spend less time worrying about fixing leaking roofs and the associated hassles — lost productivity, disruption in operations, slips and falls, repair bills, and other liabilities.

Recommending clients install a roof system that gives them the best chance of eliminating unproductive distractions is a good business decision for design/construction professionals. A more durable roof will enable property owners to focus on making profits instead of dealing with the aftermath of a roof leak.

“I have no problem endorsing asphalt-based roofing,” says Luther Mock, RRC, FRCI and founder of building envelope consultants Foursquare Solutions Inc. “The redundancy created by multiple plies of roofing is really what sets systems like BUR and modified bitumen apart.”

One can argue BUR’s closest cousin — the modified bitumen (mod bit) assembly — is actually a built-up roof made on a manufacturing line. The reality is the plies of a BUR create a redundancy that can help mitigate any potential oversights in rooftop workmanship.

BUR systems are offered in a variety of attractive and reflective options with a proven track record of performance. Photos: Johns Manville

“I’ve replaced BURs for clients I worked with 30 years ago,” says Mock. “We recently replaced [a BUR] specified in the early 1980s. And the only reason was because some of the tectum deck panels had fallen out of the assembly. Meanwhile, the roof was still performing well after 30 years.”

According to the Quality Commercial Asphalt Roofing Council of the Asphalt Roofing Manufacturers Association (ARMA), one of the main drivers of the demand for BUR systems is the desire of building owners for long life cycles for their roofs.

“A solid core of building owners and roofing professionals in North America continue to advocate asphalt-based roofing systems because of their long lives,” says Reed Hitchcock, ARMA’s executive director.

Benefits of Asphalt-Based Roofing

Over the years, asphalt-based roofing assemblies have earned a reputation for reliability with building owners, roofing consultants, architects, engineers, and commercial roofing contractors. The original price tag tends to be greater than other low-slope roofing options, but these assemblies offer competitive life-cycle costs. BUR enjoys a track record spanning more than 150 years; it provides a thick, durable roof covering and can be used in a broad range of building waterproofing applications.

An aerial view of a reflective roof membrane. Photos: Johns Manville

Available as part of fire-, wind-, and/or hail-rated systems, BUR and modified bitumen assemblies offer proven waterproofing capabilities, high tensile strength, long-term warranties, and a wide choice of top surfacings (including ‘cool’ options). Their components include the deck, vapor retarder, insulation, membrane, flashings, and surfacing material. The roofing membrane can be made up of a variety of components, including up to four high-strength roofing felts, modified bitumen membranes (hybrid systems) and standard or modified asphalt. Hot-applied asphalt typically serves as the waterproofing agent and adhesive for the system.

The roofing membrane is protected from the elements by a surfacing layer — either a cap sheet, gravel embedded in bitumen, or a coating material. Surfacings can also enhance the roofing system’s fire performance and reflectivity ratings.

Another surfacing option is gravel, commonly used in Canadian applications where the existing roof structure can handle the extra weight. There are also several smooth-surface coating options, the most popular of which are aluminum or clay emulsion products offering greater reflectivity than a smooth, black, non-gravel-surfaced roof. These reflective roof coating options are typically used in warmer regions when required by code. Reflective white roof coatings are also becoming more popular.

Cold-Process BUR

Cold application of BUR has provided an alternative to traditional hot-applied systems for more than 48 years. The term ‘cold-applied’ means the BUR roofing system is assembled using multiple plies of reinforcement applied with a liquid adhesive instead of hot asphalt. These cold adhesives are used between reinforced base/ply sheets to provide a weatherproof membrane.

The owner of this shopping mall chose BUR primarily due to its redundancy. Multiple plies of roofing can provide extra insurance against water intrusion. Photos: Johns Manville

In BUR cold-process roof systems, manufacturers typically require that only fully coated, non-porous felts (such as standard base sheets) are used as base and ply sheets. Generally, an aggregate surfacing or a coating is then applied over the completed membrane to provide surface protection and a fire rating for the roof system.

“In the re-roofing market, we’re definitely seeing more cold-applied systems being specified, particularly with modified bitumen,” says Mock. “It’s a natural alternative when a building may be occupied during the reroofing process and hot asphalt is not an option.”

Adhesives can be manually applied with a squeegee, brush, or spray application equipment. When numerous roof penetrations or rooftop access become issues, manual application of adhesives is usually the best option. Proper coverage rates are vital to a successful, long-term, cold-applied roof system. Both spray and manual application methods require the proper amount of adhesive material be installed. If too little adhesive is applied, there is a potential for an improper bond to be formed between the felts. If too much is applied, then the potential for longer setup times and membrane slippage is increased. Additionally, ambient temperatures must be 40 degrees Fahrenheit (5°C) and rising before installation. This limits, but does not preclude, use of cold-process BUR in much of the northern United States and Canada.

“I’m also comfortable specifying BUR, because I’m confident I will have a seasoned contractor on the job,” says Mock. “The commitment in terms of skilled labor and equipment is simply too great for these contractors to be first-timers.”

Flashings are another critical component of every roofing system, particularly in cold-weather applications. Four-ply BURs use modified bitumen flashings almost exclusively. These membranes are predominantly styrene butadiene styrene (SBS)-modified and offer greater elongation in frigid climates where it counts most — at the interface of the roof system with other building components.

Use of a modified-bitumen base ply is one way of handling general flashing requirements, although modified bitumen cap sheets are more common.

BUR Repair and Maintenance

Like all roof systems to some extent, the life expectancy of a BUR system depends on the property owner’s commitment to routine maintenance. All roof systems can benefit from an owner willing to undertake a proactive management plan. BUR installed over an insulation package lends itself well to non-destructive testing in the future (e.g., infrared) as a means to maximize service life.

“Asphalt roofing systems have the potential for a very long life, and preventive maintenance is the key to realizing that potential,” says Hitchcock.

Non-gravel BUR surfacing options include aggregate, a mineral surface cap sheet, or a smooth, surface-coated membrane. Photos: Johns Manville

The goal is for problem areas to be detected and fixed before they develop into leaks. Inspections can reveal potentially troublesome situations, such as a loss of gravel surfacing, which could lead to felt erosion or brittleness. Less commonly, punctures and cuts to the membrane can occur, so it is wise to remove sharp objects and debris from the roof. Clogged drains or poorly sealed flashings also present problems that are repaired easily. The effects of chemical exhausts on roofing materials should also be monitored.

Preventive maintenance actions can help catch problems before they damage larger areas of the roof system. Inspections should be performed not only on aging roofs, but also on newly-installed roofs to guard against errors in installation, design, or specifications.

BUR and modified bitumen also have a long history of proven performance in the northern United States and Canada, where snow and ice buildup are common. Perhaps more than any other roof membrane, the BUR system shrugs off minor abuse.

BUR has proven to be a low-maintenance roofing system, and it can also be effectively repaired when needed. This means property owners can usually get more life out of a BUR. The ability to enhance the performance of existing BUR membranes with coatings, mod bit cap sheets, or flood coats of asphalt explain the long service lives of these systems in demanding applications.

“Property owners rarely have to replace a four-ply BUR until it is absolutely, positively worn out,” says one roofing contractor who asked to remain anonymous. “Based on experience, these asphalt-based systems ‘hang in there’ longer than less-robust roof options.”

When BUR Is Not the Best Option

There is no roofing product solution that will fit every building specification, and that certainly holds true for BUR. Probably more than any other roofing system (except spray polyurethane foam), the built-up roofing application is more of a skill than a science. As alternative systems have been introduced into the market, the job of finding experienced BUR contractors has become more difficult. This is especially true for the hot mopping of multi-ply BUR systems.

BURs are labor intensive and their installed cost will fluctuate with crude oil prices. However, as oil prices have continued to fall, BUR manufacturers have enjoyed the lowest asphalt pricing since the 2008-09 recession. (The price of oil peaked at about $117 a barrel in September 2012 and is $50 a barrel at this writing.) Typically BUR manufacturers will pass on a portion of these savings to their customers.

BUR has always held up well in life-cycle cost analyses. However, if a roof is not expected to last 20 years or more, it usually does not make sense to specify a premium four-ply BUR.

On larger projects, gravel-surfaced BURs are typically not practical from a cost standpoint unless a source of gravel is available locally. Projects where roof access is difficult often present challenges when roofing kettles are used. And despite the preponderance of low-fuming asphalts and kettles, re-roofing occupied buildings is often unacceptable to neighbors and/or the property owner.

Built-up roofing systems have sufficient strength to resist normal expansion and contraction forces that are exerted on a roof; however, they typically have a low ability to accommodate excessive building or substrate movement. Rephrased, if the roof must be used to “hold the walls” together or if the use of “loose-laid insulation” has a benefit, then a traditional three- or four-ply built-up roofing system is not a good choice.

A built-up roof typically provides high tensile strength with low elongation. Guidelines about where expansion joints should be installed in the roofing system should not be ignored by the designer. These guidelines include installing expansion joints where the deck changes direction, approximately every 200 feet (61 meters), although many consider that this dimension can be expanded for single-ply roofing membranes; where there is a change in deck material; and, anywhere there is a structural expansion joint, etc. Based on these requirements, on some projects it simply isn’t practical to use a BUR.

BUR materials must be kept dry before and during installation to prevent blistering in the roof system. Proper storage is the key: Do not overstock the roof; use breathable tarps to cover material on the roof; store material on pallets to minimize the possibility of material sitting in water; and store rolls on-end to prevent crushing. In general, polymeric single-ply membranes like TPO (thermoplastic polyolefin) are less susceptible to storage issues.

Many roof consultants and product manufacturers clearly state that there should be no phased construction of a built-up roof. If phasing is required, then a BUR should not be specified. This is a clean and simple rule to understand; if the roof being constructed is a four-ply BUR, then only as much insulation should be installed as can be covered the same day with all four of the plies in the built-up roofing membrane. Phased construction of a built-up roof greatly increases the potential for blistering of the membrane and does not allow for the total number of plies to be installed in a shingled fashion. Phased application contains other perils, such as roofing over a small amount of overnight precipitation or dew that, even with the best of intentions, can cause harm.

As stated above, costlier modified bitumen materials should be specified for flashings and to strip in metal. Stripping in two plies of felt will most likely result in splitting at the joints in a gravel stop because the two-ply application cannot accommodate the movement in the edge metal. On new or existing buildings where significant expansion/contraction is expected, a TPO, PVC or EPDM roof membrane can save the property owners money and eliminate premature roof failure due to roof splitting.

Conclusion

Manufacturers across North America are making asphalt roofing systems like BUR better and more versatile for architects, builders, contractors, roofing consultants, and building owner/managers. Thanks especially to the addition of polymers that add stretch and strength, architects can now specify a commercial, low-slope roof as part of a multi-ply BUR system any way they want it — hot, cold, torch, or self-adhered (hybrid BUR) — to meet the individual low-slope roofing project’s needs.

Most importantly, asphalt-based roofing products offer exceptional life-cycle cost performance. They have proven to be reliable, easy to maintain, and are trusted to perform exceptionally well in extreme weather conditions.

Portable RhinoBond Hand Welder Designed for Use in Tight Spaces

OMG Roofing Products introduces the RhinoBond Hand Welder. Based on patented Sinch Technology, the portable RhinoBond Hand Welder is designed to help roofers weld RhinoBond Plates in tight spaces such as under raised rooftop equipment and on vertical surfaces. The ergonomically designed tool features a vibrating handle and an indicator light that lets roofers know when the tool is activated and when the weld cycle is complete. The base is recessed and features centering indicator lines to help users properly align the tool over installed RhinoBond Plates for optimum bonding and improved productivity.

The new tool weights just six pounds (2.7 kg), and operates on 110V and 220V power sources for global use. Each tool comes with three, eight-inch tall magnets, and a durable carrying case that protects the induction tool when not in use. Using a 12-gauge RhinoBond Power Cord (sold separately), the independent Hand Welder can be operated up to 100-feet (30 m) from the power source. A quick connect power cord pig-tail enables international users to quickly switch to the local plug configuration for global use (international pig-tails sold separately).

“Many roofers understand the tremendous productivity and performance benefits that RhinoBond offers,” said Web Shaffer, vice president of marketing for OMG. “In fact, some roofers have seen productivity rates increase by 30%. To enhance the systems’ overall productivity, we wanted to offer a solution that can be used everywhere on the roof, even in tight spaces. This new product makes that possible.”

The RhinoBond System is designed for use with TPO and PVC roofing membranes and approved by most roofing system manufacturers. The System uses advanced induction welding technology to bond roofing membranes directly to specially coated plates used to secure the insulation to the deck. The result is a roofing system with improved wind performance that requires fewer fasteners, plates, and seams, and zero penetrations of the new membrane. Since it was introduced in 1998, nearly 2.0 billion square feet (185 million square meters) of membrane has been installed with the RhinoBond System around the world.

For more information, visit OMGRoofing.com.

Single-Ply Roofing Best Practices: Doing Everything Right the First Time.

Figure 1: Designing resilient roof systems is the best of practices. When developing details, we find it very helpful to draft out the roof system (for each different system), noting materials and installation methods. Photos: Hutchinson Design Group

Single-ply membranes have risen from being the “new guy” in the market in the early ’80s to become the roof cover of choice for most architects, consultants and contractors. Material issues have for the most part been resolved, and like no other time in recent history, the industry is realizing a period of relative calm in that regard. Whether EPDM, TPO or PVC, the ease of installation, the cleanliness of the installation (versus the use of hot or cold bitumen), the speed at which they can be installed, and the material costs all blend to make these materials a viable option for watertight roofing covers. But with this market share comes issues and concerns, some of which are hurting owners, giving forensic consultants such as myself too much business, enriching attorneys, and costing contractors and, at times, designers dearly.

Following are some of my thoughts on various issues that, in my opinion, are adversely affecting single-ply membrane roof systems. Paying attention to these issues will bring about best practices in single-ply applications.

Specifying the Roof by Warranty

OMG, can architects do any less? Don’t get me started. The proliferation of “canned” Master Specs which call for a generic 10-year or 20-year warranty and then state to install the product per manufacturer’s guidelines is disheartening. Do

Figure 2: Coordinating with the mechanical engineer in the detailing of the pipe penetrations is critical. Here you can see all the components of the curb, penetrations, roofing and waterproofing are noted. We recommend that the same detail be on the mechanical sheets so that at least an 18-inch curb is known to all. Photos: Hutchinson Design Group

designers realize that manufacturers’ specifications are a market-driven minimum? When architects leave out key details, they are simply relying on the roofing contractor to do what is right. This deserves another OMG. The minimum requirements for a warranty can be very low, and the exclusions on a warranty quite extensive. Additionally, a design that calls for products to be installed based on achieving a warranty may result in a roof system that does not meet the code. Owners are often oblivious to the warranty requirements, and all too often fail to ensure the standard of care until the service life is shortened or there is storm damage — sometimes damage the roof should have withstood if it were properly designed and detailed.

If one is not knowledgeable about roof system design, detailing and specification, then a qualified roof consultant with proven experience in single-ply membranes should be retained. Roof systems and their integration into the impinging building elements need to be designed, detailed and specified appropriately for the building’s intended use and roof function. By way of example, we at Hutchinson Design Group typically design roof systems for a 40- to 50-year service life (see Figure 1); the warranty at that point is nice, but almost immaterial. Typical specifications, which are project specific, cover all the system components and their installation. They are typically 30 pages long and call out robust and enhanced material installations.

More Than the Code

I recently had a conversation with a senior member of a very large and prominent architectural firm in the Chicago area and inquired about how they go about designing the roof systems. The first thing he said was, “We do what is required by code.”

Photo 1: The roof drain sump pans shown here were provided and installed by the plumbing contractor, not the steel deck installer. Having the roof drain level with the top of the roof deck allows for a proper integration of the roof drain and roof system.

What I heard was, “We give our clients the absolute poorest roof the code allows.” An OMG is allowed here again. Does it really need to be said again that the code is a minimum standard — as some would say, the worst you are allowed to design a building by law? Maybe you didn’t realize it, but you are allowed to design above the code. I know this will shock a few of you, but yes, it’s true. Add that extra anchor to prevent wood blocking from cupping. Add extra insulation screw fasteners to improve wind uplift resistance; if too few are used, you may meet the code, but your insulation will be susceptible to cupping. Add that extra bead of polyurethane adhesive. (If I specify 4 inches on center, then perhaps by mid-day, on a hot and humid day, I might get 6 inches on center — as opposed to specifying 6 inches or 8 inches on center, and getting 12 inches on center in spots.) Plan for construction tolerances such as an uneven decks and poorly constructed walls. Allow for foot traffic by other trades. These types of enhancements come from empirical experiences — otherwise known as getting your butt in the ringer. Architects need more time on the roof to observe what goes on.

It’s About Doing What is Right

Doing it right the first time isn’t all that difficult, and it’s certainly less stressful than dealing with the aftermath of doing so little. The cost of replacing the roof in the future could easily be more than double the original cost. Twenty years ago, I

Figure 3: Coordinating with the plumbing engineer, like coordinating with the mechanical engineer, is a requirement of best practices. In this drain detail, we can see the sump pan is called out correctly, and the roof drain, integration of the vapor barrier, extension ring, etc., are clearly defined. Photos: Hutchinson Design Group

chaired an international committee on sustainable low-slope roofing. At that time, the understanding of sustainability was nil, and I believe the committee’s Tenets of Sustainability, translated into 12 languages, helped set the stage for getting designers to understand that the essence of sustainability is long-term service life. That mantra seems to have been lost as a new generation of architects is at the helm. This is unfortunate, as it comes at a time when clients no longer ask for sustainable buildings. Why? Because they are now expected. The recent rash of violent and destructive storms — hurricanes, hail, intense rain, high winds and even wildfires — have resulted in calls for improvement. That improvement is called resiliency. If you have not heard of it, you are already behind. Where sustainability calls for a building to minimize the impact of the building (roof) on the environment, resiliency requires a building (roof) to minimize the impact of the environment on the building. This concept of resiliency requires designing a roof system to weather intense storms and to be easily repaired when damaged. (Think of Puerto Rico and consider how you would repair a roof with no power, limited access to materials, and manpower that might not be able to get to your site.)

Achieving resiliency requires the roof system designer to:

  1. Actually understand that roofs are systems and only as good as their weakest link. Think metal stud parapet and horizontal base anchor attachment; only forensic consultants and attorneys like to see screws into modified gypsum boards.
  2. Eliminate your old, out-of-date, incorrect details. Lead vent flashing and roof cement cannot be used with single-ply membrane.
  3. Design the roof system integration into associated barrier systems, such as where the roofing membrane (air/vapor retarder) meets the wall air barrier. You should be able to take a pencil and draw a line over the wall air barrier, up the wall and onto the roof without lifting it off the sheet. If you cannot, you need to redesign. Once you can, you need to consider constructability and who may get there first — the roofer or air barrier contractor. Then think material compatibility. Water-based air barrier systems don’t react well when hit with a solvent-based primer or adhesive.

    Photo 2: This roof drain is properly installed along with 6 inches of insulation and a cover board. The drain extension ring is 1/2 inch below the top of the cover board so that the water falls into the drain and is not held back by the clamping ring, resulting in ponding around the roof drain.

    Perhaps the roofing needs to be in place first, and then the air barrier brought over the top of the roofing material. This might require a stainless-steel transition piece for incompatible materials. Maybe this requires a self-adhering membrane over the top of the roof edge prior to the roofing work, as some membranes are rather rigid and do not bend well over 90-degree angles. You as the designer need to design this connectivity and detail it large and bold for all to see.

  4. Design the roof system’s integration into the impinging building elements, including:
  • Roof curbs for exhaust fans: Make sure they are insulated, of great enough height, and are not installed on wood blocking.
  • Rooftop unit (RTU) curbs: The height must allow for future re-roofing. Coordinate with the mechanical engineer regarding constructability – determine when the curb should be set and when the HVAC unit will be installed. Roof details should be on both the architectural and mechanical drawings and show the same curb, drawn to scale. Be sure the curb is insulated to the roof’s required R-value. Avoid using curb rails to support mechanical equipment. The flashing on the interior side of the rails may be inaccessible once the equipment is placed. Use a large curb where all four sides will remain accessible.
  • Piping penetrations: Detail mechanical piping penetrations through the roof and support of same, where insulation and waterproofed pipe curbs are needed (see Figure 2). If you are thinking pourable sealer pocket, stop reading and go sign up for RCI’s Basics of Roof Consulting course.
  • Roof curbs, RTU, pipe curbs and rails: Coordinate their location and show them on the roof plan to be assured that they are not inhibiting drainage.
  • Roof drains: Coordination with the plumbing engineer is essential. Sump pans should be installed by the plumbing contractor, not the steel deck installer (see Photo 1), and the location should be confirmed with the structural engineer. Be sure drains are located in the low point if the roof deck is structurally sloped — and if not, know how to design tapered insulation systems to move water up that slope. Do not hold drains off the deck to meet insulation thickness; use threaded extensions. Be sure any air/vapor barrier is integrated into the curb and that the insulation is sealed to the curb. I like to hold the drain flange a half-inch down below the insulation surface so that the clamping ring does not restrain water on the surface. Owners do not like to see a 3-foot black ring at the drain, where ponding water accumulates debris (see Figure 3 and Photo 2).
  1. Understand the roof’s intended use once the building is completed. Will the roof’s surface be used for anything besides weather protection? What about snow removal? Will there be excessive foot traffic? What about mechanical

    Photo 3: Gaps between the roof insulation and roof edges, curbs and penetrations are prevalent on most roofing projects and should be sealed with spray foam insulation as seen here. It will be trimmed flush once cured.

    equipment? Photovoltaic panels? Yes, we have designed roofs in which a forklift had to go between penthouses across the roof. Understanding how the roof will be used will help you immensely.

  2. Understand the construction process and how the roof might be used during construction. It is amazing how few architects know how a building is built and understand construction sequencing and the impact it can have on a roof. I firmly believe that architects think that after a lower roof is completed, that the masons, carpenters, glazers, sheet metal workers, welders, pipe fitters, and mechanical crews take time to fully protect the newly installed systems (often of minimal thickness and, here we go again, without a cover board — OMG) before working on them. I think not. Had the architect realized that temporary/vapor retarders could be installed as work surfaces, getting the building into the dry and allowing other trades to trash that rather than the finished roof, the roof system could be installed after those trades are off the roof.
  3. Coordinate with other disciplines. Roof systems cannot be designed in a vacuum. The architect needs to talk to and involve the structural, mechanical and plumbing engineers to ensure they realize the importance of essential details. For example, we cannot have steel angle around the drain whose flange rests on the bar joist, thus raising the roof deck surface at the roof drain. Ever wonder why you had ponding at the drain? Now you know. I attempt to always have a comprehensive, specific roofing detail on the structural, mechanical and plumbing sheets. I give the other disciplines my details and ask that they include them on their drawings, changing notes as required. That way, my 20-inch roof curb on the roof detail is a 20-inch curb on the mechanical sheets — not a standard 12-inch curb, which would more often than not be buried in insulation.
  4. Detail, detail, detail, and in case you glossed over this section, detail again. Make sure to include job-specific, clearly drawn details. Every condition of the roof should be detailed by the architect. Isn’t that what the client is paying for? Do not, as I once saw, indicate “RFO” on the drawings. Yes, that acronym stands for “Roofer Figure Out.” Apparently, the roofer did not figure it out. I enjoyed a nice Hawaiian vacation as a result of my work on that project, courtesy of the architect’s insurance company. How do you know that a condition works unless you design it and then draw it to scale?

    Figure 4: Insulation to curbs, roof edge and penetrations will not be tight, and to prevent a thermal short, the gaps created in construction need to filled with spray foam, as noted and shown here in this vent detail. Photos: Hutchinson Design Group

    I’ve seen roof insulation several inches above the roof edge because, OMG, the architect wanted gravel stop and forgot about camber. Not too big a deal (unless of course it’s a large building) to add several more layers of wood blocking and tapered edge strips at the now high wood blocking in the areas that were flush, but now the face of the roof edge sheet metal needs to increase. But what if the increase is above the allowable ANSI-SPRI ES1 standard and now a fascia and clip are required? You can see how the cost spirals, and the discussion ensues about who pays for what when there is a design error.

  5. Develop comprehensive specifications that indicate how the roof system components are to be installed. This requires empirical knowledge, the result of time on the roof observing construction. It is a very important educational tool that can prevent you, the designer, from looking like a fool.

Components

Best practices for single-ply membranes, in addition to the design elements above, also involve the system components. Below is a listing of items I feel embodies best practices for single-ply roof system components:

  1. Thicker membranes: The 45-mil membrane is insufficient for best practices, especially when one considers the thickness of the waterproofing over scrim on reinforced sheets. A 60-mil membrane is in my opinion the best practices minimum. Hear that? It’s the minimum. You are allowed to go to 75, 80 or 90 mils.
  2. Cover boards: A cover board should be specified in fully adhered and mechanically attached systems. (Ballasted systems should not incorporate a cover board.) Cover boards have enhanced adhesion of the membrane to the substrate over insulation facers and hold up better under wind load and hail. Cover boards also protect the insulation

    Photo 4: The greatest concern with the use of polyurethane adhesives is that the insulation board might not be not fully embedded into the adhesive. Weighting the boards at the corners and center with a minimum of 35 pounds for 10 minutes has proven to work well in achieving a solid bond.

    from physical damage and remain robust under foot traffic, while insulation tends to become crushed. Cover boards are dominated by the use of mat-faced modified gypsum products. Hydroscopic cover boards such as fiberboards are not recommended.

  3. Insulation: Now here is a product that designers seldom realize has many parts to be considered. First, let’s look at compression strength. If you are looking to best practices, 25 psi minimum is the way to go. The 18-psi insulation products with a fiber reinforced paper facer can be ruled out entirely, while 20 psi products are OK for ballasted systems. Now let’s look at facers. If you think about it for a second, when I say “paper-faced insulation,” you should first think “moisture absorbing” and secondly “mold growth.” Thus paper-faced products are not recommended to be incorporated if you are using best practices. You should be specifying the coated glass-faced products, which are resistant to moisture and mold resistant. A note to the manufacturers: get your acts together and be able to provide this product in a timely manner.

Additional considerations regarding insulation:

  • Insulation joints and gaps: You just can’t leave joints and gaps open. Show filling the open joints at the perimeter and curbs and around penetrations with spray foam in your details and specify this as well (see Photo 3 and Figure 4).
  • Mechanical attachment: Define the method of attachment and keep it simple. On typical projects, I commonly specify one mechanical fastener every 2 square feet over the entire roof (unless more fasteners are needed in the corners). Reducing the number of fasteners in the field compared to the perimeter can be confusing for contractors and the quality assurance observer, especially when the architect doesn’t define where that line is. The cost of the additional screws is nominal compared with the overall cost of the roof.
  • Polyurethane foam adhesive: Full cover spray foam or bead foam adhesive is taking over for asphalt, at least here in the Midwest, and I suspect in other local markets as well. The foam adhesive is great. It sticks to everything: cars, skylights, clerestories, your sunglasses. So, it is amazing how many insulation boards go down and don’t touch the foam. You must specify that the boards need to be set into place, walked on and then weighted in place until set. We specify five 35-pound weights (a 5-gallon pail filled with water works nicely), one at each corner and one in the middle for 10 minutes (see Photo 4). Yes, you need to be that specific.
  1. Photo 5: The design of exterior walls with metal studs that project above the roof deck is a multi-faceted, high-risk detail that is often poorly executed. Here you can see a gap between the deck and wall through which warm moist air will move and result in the premature failure of this roof. The sheathing on the wall cannot hold the horizontal base anchor screw, and the joints in the board allow air to pass to the base flashing, where is will condense. This is the type of architectural design that keeps on giving — giving me future work.

    Vapor/air barrier: A vapor air barrier can certainly serve more than a function as required for, say, over wet room conditions: pools, locker rooms, kitchens, gymnasiums. We incorporate them in both new construction and re-roofing as a means of addressing construction trade phasing and, for re-roofing, allowing time for the proper modification of existing elements such as roof edges, curbs, vents, drains, skylights and pipe curbs. Be sure to detail the penetrations and tie-ins with wall components.

  2. Deck type: Robust roof decks are best. Specify 80 ksi steel roof decks. Try staying away from joint spacing over 5 feet. Decks should be fully supported and extend completely to roof edges and curbs.
  3. Roof edge design: A key aesthetic concern, the termination point for the roof system, the first line of defense in regard to wind safety — the roof edge is all of these. The construction of the roof edge on typical commercial construction has changed drastically in the last 20 years, from brick and block to metal stud. Poorly designed metal stud parapets will be funding my grandkids’ college education. The challenge for the metal stud design is multifaceted: It must close off the chimney effect, prevent warm moist air from rising and condensing on the steel and wall substrate, create an acceptable substrate on the stud face in which to accept base anchor attachment, and — oh, yes — let’s not forget fire issues. Tread lightly here and create a “big stick” design (see Photo 5).
  4. Roof drains and curbs: As discussed above, there is a great need for coordination and specific detailing here. The rewards will be substantial in regard to quality and efficiency, minimizing time spent dealing with “what do we do now” scenarios.
  5. Slope: Design new structures with structural roof deck slope, then fine tune with tapered insulation.

Final Thoughts

Best practices will always be a balancing act between cost and quality. I believe in the mantra of “doing it right the first time.”

The industry has the material and contractors possess the skill. It’s the design and graphic communication arm that needs to improve to keep everyone working at the top of their game.

Designers, get out in the field and see the results of your details. See firsthand how a gypsum-based substrate board on a stud wall does not hold screws well; how a lap joint may not seal over the leading edge of tapered insulation; how the roof either ponds water at the roof drain or doesn’t meet code by drastically sumping; or how the hole cut in the roof membrane for the drain might be smaller than the drain bowl flange, thus restricting drainage. Seeing issues that the contractors deal with will help you as the designer in developing better details.

Contractors, when you see a detail that doesn’t work during the bidding, send in an RFI and not only ask a question, but take the time to inform the architect why you don’t think it will work. On a recent project here in Chicago, the architect omitted the vapor retarder over a pool. The contractor wrote an explicit explanation letter and RFI to the architect during bidding, and the architect replied, “install as designed.” In these situations, just walk away. For me, this is future work. A local contractor once told me, “I don’t get paid to RFI, I get paid to change order.” He also said, “If I ever received a response to an RFI, I would frame it!”

Manufacturers, too, can raise the bar. How about prohibiting loose base flashings at all times, and not allowing it when the salesman says the competition is allowing it. Have contractors on the cusp of quality? Decertify them. You don’t need the hassles. Owners don’t need the risk.

Seek out and welcome collaboration among contractors, roof systems designers, knowledgeable roof consultants, and engineers. Learning is a lifelong process, and the bar is changing every year. Too often we can be closed off and choose not to listen. At HDG, I am proud to say we have the building owners’ best interests at heart.

By all working together, the future of single-ply membranes can be enhanced and the systems will be retained when the next generation of roof cover arrives — and you know it will.

PVC System Is the Answer for U.S. Bank Stadium Roof

U.S. Bank Stadium is topped with a PVC roof system that display’s the company’s logo. Photo: Johns Manville

When discussions began about the new U.S. Bank Stadium in Minneapolis, Minnesota, there was a request for an outdoor stadium. However, state and local government provided funding specifically for an indoor stadium that would be able to host major events like the professional football championship game and the college basketball championship game. As a result, a translucent roof and mobile front windows were designed to allow natural light to enter the stadium and to give fans a view of downtown Minneapolis. The mobile windows also allow fans to experience outdoor elements while providing protection from snow, rain and cold winter weather. The roof design was developed taking into consideration the budget and the region’s weather; it would be costly to make it retractable, and a sloped roof lends to a more secure option for snowy weather.

Challenging Task

Berwald Roofing Company Inc., headquartered in North St. Paul, Minnesota, installed an adhered PVC roof system manufactured by Johns Manville over the structure’s metal deck. In all, 280,000 square feet of grey 60-mil PVC were installed. The system also included a vapor barrier and two layers of 1.6-inch ENRGY 3, a rigid roof insulation board composed of a closed-cell polyisocyanurate foam core with fiberglass reinforced facers. Half-inch DensDeck Prime cover board from Georgia-Pacific was also installed.

The roofing portion of the project began in April 2015, with an aggressive completion deadline of November 1, 2015. The schedule and logistics on the project posed major hurdles. “Getting material 300 feet up to the roof was our biggest challenge,” says Berwald Roofing Senior Project Manager Steven Hegge. “A big part of that was scheduling time to share the cranes with the iron workers and general contractor.”

Another challenge was storing material during the installation due to the limited amount of space on the roof. “All the decking had to be installed as we went along, just before roof installation,” Hegge states. “We were on a very tight time schedule in this multiple-phase construction project.”

“The general contractor and Berwald Roofing have worked with Johns Manville on numerous stadium projects in the past and preferred to use JM PVC on this complicated stadium project,” notes Johns Manville sales rep Bob Deans. “This application is on a 3.75-inch to 12-inch slope on the north side of the building, which adds to the difficulty of installing a fully adhered PVC roof assembly.”

The Solution

Due to restricted loading space at the jobsite, materials arrived to Berwald’s yard directly from the manufacturer. They were then loaded on Berwald Roofing semi-trucks each day for delivery. Once they arrived at the site, they were immediately lifted to the roof via tower cranes and installed in the most efficient time frame, to meet the owners expected installation timeline.

The stadium seats approximately 65,000 people for most games. However, this space is built to be expandable to hold up to 73,000 attendees for special events such as the professional football championship game, which the stadium is scheduled to host on February 4, 2018, and for events like the college basketball championship game, which will be held there in 2019. U.S. Bank’s logo is prominently displayed on the rooftop. Charcoal grey 60-mil PVC membrane was cut to specification using a computerized cutter to create an exact replica of the U.S. Bank logo. Berwald Roofing then adhered the charcoal grey PVC on top of the grey 60 mil PVC membrane using JM PVC low-VOC membrane adhesive and then heat-welded the edges of material to finish the application of the logo.

TEAM

Architects: HKS Inc., www.hksinc.com; Studio Hive, www.studiohive.com; Studio Five; and Lawal Scott Erickson Architects Inc., http://lse-architects.com
General Contractor: Mortenson Construction, Minneapolis, Minnesota, www.mortenson.com
Roofing Contractor: Berwald Roofing Company Inc., North St. Paul, Minnesota, https://berwaldroofing.com

MATERIALS

Roof System: 60-mil PVC, Johns Manville, www.jm.com/roofing
Vapor Barrier: Johns Manville
Insulation: ENRGY 3® Insulation, Johns Manville
Cover Board: DensDeck Prime, Georgia-Pacific, www.gp.com

Hyload Adds to Product Portfolio

Hyload Inc., manufacturer and supplier of roofing and waterproofing solutions, announced the addition of a white, scrim re-enforced PVC membrane, as well as fleece-backed PVC membrane, to its product offering. Hyload is also offering three grades of modified bitumen roof membranes: fully adhered, torch grade, and an APP membrane.

Hyload’s current product offering includes through-wall flashing, membrane roofing, waterproofing and green roof systems. According to Dave Afanador, Business Development Manager at Hyload, “The additions round out our hugely successful offering of highly durable KEE membrane with other chemistries to assist in specifying roof membranes that are specific to the needs and price points of all of our current and future customers.”

For more information, visit www.Hyload.com.

Plate Marking Tool Designed to Increase Installation Efficiency

OMG Roofing Products introduces a plate marking tool designed to help roofers improve rooftop productivity by quickly locating and marking RhinoBond Plates installed under thermoplastic membranes.  

The new RhinoBond Plate Marking Tool is lightweight, simple-to-use and easy-to-maneuver. Simply roll the marking tool over a row of installed RhinoBond Plates. Every time it passes over a properly installed plate, the tool leaves a temporary mark on the surface of the membrane to identify the plate location. Plate marks are made with standard blue construction crayons and typically fade away within a few weeks.

The plate marking tool is compatible with all thermoplastic membranes regardless of type or thickness. In addition, the tool’s handle is reversible for quick direction changes, and lays flat for rolling under rooftop pipes and raised equipment such as air handling units. Other benefits of the new system include powerful sweeper magnets mounted on the front and back of the chassis that pick-up any metal debris on the roof. The tool is provided in a protective carrying case for easy handling and storage.

The RhinoBond System is designed for use with TPO and PVC roofing membranes. The System uses advanced induction welding technology to bond roofing membranes directly to specially coated plates that secure the insulation to the deck. The result is a roofing system with improved wind performance that requires fewer fasteners, plates, and seams, and zero penetrations of the new membrane.

For more information, visit OMGRoofing.com.

Metal Barrel Roof Tops the Rebels’ New Basketball Arena

The Pavilion at Ole Miss seats 9,500 fans.

The Pavilion at Ole Miss seats 9,500 fans. The building’s signature is its standing seam metal roof, which was manufactured by ACI Building Systems. Photos: Professional Roofing Contractors Inc.

The Pavilion at Ole Miss is a multi-purpose facility that is most famous for hosting the University of Mississippi’s basketball team. The arena cost approximately $97 million to build and seats 9,500 fans. The building’s signature arched metal panel roof was designed to complement the curved entrance and blend in with other architectural features on the university’s campus in Oxford, Miss.

Professional Roofing Contractors of Shelbyville, Tenn., was originally called in to assist with estimating the cost of the structure’s main roof, as well as a membrane roof system on the lower level. Upon final bid results, the decision was made to proceed with a standing seam metal roof on the upper portion of the building and a PVC roof on the lower level. Professional Roofing was the successful low roof bidder and selected ACI Building Systems to provide the standing seam roof materials and Sika Sarnafil to provide the PVC membrane roof materials. Professional Roofing installed both systems, with Jose Martinez as the crew leader for the membrane roofing portion and Dale Jones in charge of the metal roofing crew.

Larry W. Price, president of Professional Roofing, and Jonathan Price, the company’s vice president and the production manager on the project, oversaw the installation of 79,500 square feet of standing seam metal roofing and 46,500 square feet of PVC. There wasn’t much room for staging material on the jobsite, which didn’t give the company much room to maneuver. For the main roof, bundles of pre-cut metal panels were trailered in by ACI and loaded to the roof by crane.

“Logistics were complicated,” notes Larry Price. “Just getting a big enough crane in there and lifting the panels was difficult. Once we got the panels on the roof and they were situated, the roofers could just move ahead.”

Photos: Professional Roofing Contractors Inc.

Photos: Professional Roofing Contractors Inc.

Panels were installed with a 2-inch-high, double-lock standing seam, which was completed using a self-propelled mechanical seamer from D.I. Roof Seamers. The metal panels were curved into place by crews on the roof, who installed them over the staggered metal deck after it was covered with two 2-inch layers of polyiso insulation and Carlisle’s WIP 300 HT self-adhered underlayment. “The metal deck was segmented,” notes Jonathan Price. “We had to bridge some of those sections to make a nice, smooth curve.”

The scope of work included a large gutter at the roof edge. The gutter was 3 feet high and 2 feet wide, and crews from Professional Roofing flashed the gutter and lined it with the same Sika Sarnafil PVC used on the lower roof.

On the mezzanine level, crews installed a vapor barrier and mechanically fastened two 2-inch layers of polyiso insulation, as well as some tapered insulation for drainage. Once that work was completed, the 60-mil PVC was applied.

“Everything went pretty smoothly,” says Jonathan Price. “Logistics are usually tight on a new construction project, but once we adjusted to that, we just had to cope with the weather.”

“We had a lot of hot days and some rainy days,” Larry Price remembers. “Mississippi in the summer can get hot, hot, hot—and when it’s not hot, it’s raining.”

TEAM

Architect: AECOM, Kansas City, Mo.
General Contractor: BL Harbert International, Birmingham, Ala., Blharbert.com
Roofing Contractor: Professional Roofing Contractors Inc., Shelbyville, Tenn., Professionalroofingcontractors.com
Metal Roof Panel Manufacturer: ACI Building Systems, LLC, ACIbuildingsystems.com
PVC Roof Manufacturer: Sika Sarnafil, USA.sarnafil.sika.com