Roofing in Romania: Lessons From the Past

[Editor’s Note: In May, Thomas W. Hutchinson presented a paper at the 2017 International Conference on Building Envelope Systems and Technologies (ICBEST) in Istanbul, Turkey, as did his good friend, Dr. Ana-Maria Dabija. After the conference, Hutchinson delivered a lecture to the architectural students at the University of Architecture in Bucharest, Romania, and spent several days touring Romania, exploring the country’s historic buildings and new architecture. Convinced that readers in the United States would appreciate information on how other countries treat roofing, he asked Dr. Dabija to report on roof systems in Romania in the first of what is hoped to be a series of articles on roofing in foreign countries.]

Photo 1. Sanctuary in Sarmizegetusa Regia. Photo: Oroles. Public Domain.

Photo 1. Sanctuary in Sarmizegetusa Regia. Photo: Oroles. Public Domain.

Romania is somewhere in the Southeastern part of Europe, in a stunning landscape: an almost round-shaped country, with a crown of mountains—Carpathians—that close the Transylvanian highlands, with rivers that flow towards the plains, that merge into the Danube and flow to the Black Sea.

Conquered by the Romans in 106 A.D, crossed by the migrators between the fourth and the eighth centuries, split in three historic provinces—Walachia, Moldova and Transylvania—and squeezed between empires, Romania absorbed features from all the people and civilizations that passed through or stayed in its territories.

The language—Latin in its structure—has ancient Dacian words that blend in with words from languages from other countries that had influence in our history: Greek, French, Turkish, English, Slavonic, Serbian, German, Hungarian. Traditional foods vary by region; for instance, in Transylvania you won’t find fish, while at the seaside, in the Danube Delta, on the banks of the rivers, fish is traditional. Each historic province uses different ingredients and developed recipes that can be found in Austria and Hungary, in Greece and Turkey, in Russia and Ukraine.

The same applies to buildings. In Transylvania, the Austrian Empire hallmarked the houses in the villages, the mansions, the palaces, the churches, the administrative buildings. One of the most popular sites for foreign tourists is the Bran Castle, infamous home of Dracula. In Walachia, the buildings have strong Balkan influences. Close to the Black Sea, the Turkish and the Greek communities that settled there brought the style of the countries they came from. Moldova was under the influence of the Russian Empire reaching back to Peter the Great.

Photo 2. Densuș church, Hațeg County, has a roof made of stone plates. Photo: Alexandru Baboș, Creative Common Attribution.

Photo 2. Densuș church, Hațeg County, has a roof made of stone plates. Photo: Alexandru Baboș, Creative Common Attribution.

Romania is situated in the Northern hemisphere, about halfway between the Equator and the North Pole. The climate features hot, dry summers with temperatures that can rise to 113 degrees Fahrenheit in the South, and cold winters, with temperatures that can drop to minus 22 degrees in the depressions of Transylvania, with heavy snow and strong winds. There are some spots with milder temperatures, close to the sea and in the western part of the country.

Why all this introduction? Because specific geographic conditions lead to specific building systems. People living in areas with abundant rain and snow need materials and systems that resist and shed water; after all, the steeper the slope, the faster the water is evacuated off the roof.

Cultural influences color the patrimony, but climatic conditions define the geometry and the materials that are used for roofs. As there are different climatic conditions as well as diverse cultural influences, the building typologies of the roofs are, in their turn, diverse.

Ancient Settlements

Photo 3. Below-ground cottage in the Village Museum in Bucharest. Photo: Ana-Maria Dabija.

Photo 3. Below-ground cottage in the Village Museum in Bucharest. Photo: Ana-Maria Dabija.

Although these territories were inhabited for millennia, the roofs did not “travel” in time as long as the walls. The six ancient citadels of the Dacians, located almost in the center of Romania in the southwestern side of the Transylvanian highlands, still preserve ruins of the limestone, andesite or wooden columns of the shrines, altars, palaces and agoras. No roofs survived. (See Photo 1.) We can only presume that the materials that were used for the roofing were wood shingles or thatch, which would explain both why artefacts of the roofs could not be found and also why the deterioration is so advanced.

After Rome conquered Dacia, emperor Trajanus built a citadel that was supposed to represent continuity with the previous civilization: the Sarmizegetusa Ulpia Traiana. It seems to have had an active life, considering the temples, palaces and dwellings that we inherited, including an amphitheater for 5,000 people. Still, no roofing traces survived.

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Hot-Air Welding Under Changing Environmental Conditions

The robotic welder’s speed, heat output and pressure should be properly programmed before the welding process begins. Photo: Leister.

The robotic welder’s speed, heat output and pressure should be properly programmed before the welding process begins. Photo: Leister.

Today’s most powerful hot-air welders for overlap welding of thermoplastic membranes are advertised to achieve speeds of up to 18 meters (59 feet) per minute. That’s fast enough to quickly ruin a roofing contractor’s day.

These robotic welders are digitally monitored to achieve consistent overlap welding performance, but they cannot adapt to changing environmental conditions automatically. It’s the contractor’s job to monitor and assess seam quality before the base seam is welded and when ambient temperatures or other factors potentially influence welding performance.

Successful hot-air welding requires the use of specialized, properly maintained and adjusted equipment operated by experienced personnel familiar with hot-air welding techniques. Achieving consistent welds is a function of ensuring that the roofing membrane surface is clean and prepared for heat welding, conducting test welds to determine proper equipment settings, and evaluating weld quality after welding has been completed.

Setting up hot-air robotic welders properly is the key to having a properly installed thermoplastic roof, and performing test welds is one of the most important steps. Making appropriate adjustments before the welding process begins ensures that the correct combination of welder speed, heat output and pressure is programmed into the robotic welder.

For most roofing professionals, these procedures have been firmly established in the minds of their crews and equipment operators through education and field training. But let’s not forget that Murphy’s Law often rules on both large and small low-slope roofing projects.

The frightening reality about using robotic welders is if they are set-up incorrectly or environmental conditions change, the applicator may weld thousands of feet of non-spec seam before anyone even bothers to check. If you probe for voids at the end of the day, it is probably too late.

If serious problems are discovered, the applicator must strip in a new weld via adhesive, cover tape, or heat welding, depending on what the membrane manufacturer will allow. If seams must be re-welded, the operator has to create not one, but two robotic welds on each side of the cover strip. The sheet will also need to be cleaned and re-conditioned no matter what method is used.

Can these errors be corrected? Absolutely. Except now the crew is in a real hurry because the roofer is working on his own time, and application errors tend to snowball under these conditions.

Reality Check

What goes on in the field is sometimes quite different than what one sees when hot-air welding thermoplastics under an expert’s supervision.To support this view, we asked four field service reps, each with a minimum of 35 years of roofing experience, to comment. The most senior “tech” has worked for six different thermoplastic membrane manufacturers in his career. Their names shall remain anonymous, but this writer will be happy to put readers in touch with them upon request.

Successful hand welding is a skill that is developed and refined over time. The correct selection of welder temperature and nozzle width can have a significant effect on the quality of the hand weld. Photo: GAF.

Successful hand welding is a skill that is developed and refined over time. The correct selection of welder temperature and nozzle width can have a significant effect on the quality of the hand weld. Photo: GAF.

So, let’s welcome Christian, Dave, Mark and Walter, and get straight to the point: Is the average roofing crew diligent enough when it comes to properly testing welds using industry best practices?

“I would say ‘probably not,” exclaims Walter. Dave just shakes his head as his colleague Mark adds, “I would have to say no.”

Considering the generally laudable performance of thermoplastic membranes over the last decade or so, we must interpret our experts’ opinions as suggesting the need for further improvement in hot-air welding techniques. Hence, the purpose of this article.

“There are a few outstanding issues causing bad welds,” says Walter. “These include welding over dirty or contaminated membranes; improper equipment setup; using crews with inadequate training; and knowing the difference between the weldability of various manufacturers’ membranes.”

Welding equipment consists of three main components: the power supply, the hot air welder (either automatic or hand-held), and the extension cord. A stable power supply of adequate wattage and consistent voltage is critical to obtaining consistent hot air welds and to prevent damage to the welder.

The use of a contractor-supplied portable generator is recommended, although house-supplied power may be acceptable. Relying on power sources that are used for other equipment that cycle on and off is not recommended. Power surges and/or disruptions and insufficient power may also impact welding quality. Proper maintenance of welding equipment is also of obvious importance.

“Contractors seem to never have enough power on the roof,” observes Mark. “The more consistent your power is, the more consistent your welds will be. Too many times, I’ve seen too many tools (hand guns, auto welder, screw guns and a RhinoBond machine) plugged into one generator.”

Generator-induced challenges on the jobsite are going to arise, agrees Christian. “But at least today there is more experience in understanding, dealing with, and ultimately preventing these issues,” he says.

Most TPO and PVC membrane suppliers also recommend using the latest automatic welding equipment, which provides improved control of speed, temperature and pressure. Our four experts generally agree that field welding performance has improved over the years and programmable robotic welders have helped. They also point to proper training and experience as crucial factors.

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Definition of Resilience: Hospital Provides a Lesson in Preparing for Weather Events

Staten Island University Hospital escaped major damage during Hurricane Sandy. The city of New York allocated $28 million to fund the hospital’s resiliency plan, and the state contributed an additional $12 million.

Staten Island University Hospital escaped major damage during Hurricane Sandy. The city of New York allocated $28 million to fund the hospital’s resiliency plan, and the state contributed an additional $12 million.

Almost five years ago, Hurricane Sandy bore down on New York City with winds that reached gusts of 100 miles an hour and a storm surge 16 feet above normal that flooded huge parts of the city. Entire neighborhoods lost electricity for several days, the Stock Exchange closed during and immediately after the storm, and scuba divers were called in to assess damage in parts of the city’s submerged subway system.

Staten Island, one of New York’s five boroughs, was heavily damaged. Its position in New York Harbor, at the intersection of the coastlines of Long Island and New Jersey, leaves the island particularly exposed to storm surge during extreme weather events. A geologist from Woods Hole Oceanographic Institution in Massachusetts described Staten Island as being, “at the end of, basically, a big funnel between New Jersey and New York.”

Staten Island University Hospital almost miraculously escaped major damage, despite flood waters coming within inches of it doors. The hospital stayed open during and after Hurricane Sandy, continuing to provide vital services despite the storm. The hospital is home to the largest emergency room on Staten Island, and houses more than one third of the borough’s in-patient beds. New York Mayor DeBlasio has called the hospital, “a truly decisive healthcare facility—even more so in times of crisis.”

While both hospital and city officials were relieved that the facility had escaped Sandy largely unharmed, the lesson that Sandy delivered was taken to heart: major mitigation efforts were needed if the hospital expected to survive similar storms in the future. With this in mind, the city of New York allocated $28 million to fund the hospital’s resiliency plan, with the state kicking in an additional $12 million.

The money is being spent on three major projects to better prepare the hospital for future storms: the elevation of critical building power and mechanical systems, the installation of sanitary holding tanks and backflow prevention, and the installation of major wind resiliency and roofing improvements. 

Resilient Design

The Staten Island experience, and the plan to upgrade its ability to withstand major weather events, is hardly unique. Nationwide, resilient design has become a major focus of the construction community.

Hurricane Sandy certainly intensified the sense of urgency surrounding the need for resilience. But well before that, Hurricane Katrina, in 2005, provided a tragic case study on the fragility of seemingly stable structures, as the storm brought a small, poor southern city to the brink of chaos and devastated entire neighborhoods. While these two hurricanes drew national and international attention, communities throughout the country have also been dealing with frequent, erratic and intense weather events that disrupted daily life, resulting in economic losses and, all too often, the loss of human life. These emergencies may include catastrophic natural disasters, such as hurricanes, earthquakes, sinkholes, fires, floods, tornadoes, hailstorms, and volcanic activity. They also refer to man-made events such as acts of terrorism, release of radioactive materials or other toxic waste, wildfires and hazardous material spills.

The focus, to a certain degree, is on upgrading structures that have been damaged in natural disasters. But even more, architects and building owners are focusing on building resilience into the fabric of a structure to mitigate the impact of future devastating weather events. And, as with the Staten Island Hospital, the roof is getting new attention as an important component of a truly resilient structure.

The resilience of the roofing system is a critical component in helping a building withstand a storm and rebound quickly. In addition, a robust roofing system can help maintain a habitable temperature in a building in case of loss of power. Photo: Hutchinson Design Group.

The resilience of the roofing system is a critical component in helping a building withstand a storm and rebound quickly. In addition, a robust roofing system can help maintain a habitable temperature in a building in case of loss of power. Photo: Hutchinson Design Group.

So, what is resilience, how is it defined, and why is it important to buildings in differing climates facing unique weather events? The Department of Homeland Security defines resilience as “the ability to adapt to changing conditions and withstand and rapidly recover from disruption due to emergencies.” The key words here are “adapt” and “rapidly recover.” In other words, resilience is measured in a structure’s ability to quickly return to normal after a damaging event. And the resilience of the roofing system, an essential element in protecting the integrity of a building, is a critical component in rebounding quickly. In addition, a robust roofing system can provide a critical evacuation path in an emergency, and can help maintain a habitable temperature in a building in case of loss of power.

According to a Resilience Task Force convened by the EPDM Roofing Association (ERA), two factors determine the resiliency of a roofing system: durable components and a robust design. Durable components are characterized by:
Outstanding weathering characteristics in all climates (UV resistance, and the ability to withstand extreme heat and cold).

  • Ease of maintenance and repair.
  • Excellent impact resistance.
  • Ability to withstand moderate movement cycles without fatigue.
  • Good fire resistance (low combustibility) and basic chemical resistance.
  • A robust design that will enhance the resiliency of a roofing system should incorporate:

  • Redundancy in the form of a backup system and/or waterproofing layer.
  • The ability to resist extreme weather events, climate change or change in building use.
  • Excellent wind uplift resistance, but most importantly multiple cycling to the limits of its adhesion.
  • Easily repaired with common tools and readily accessible materials.
  • More Information on Resilient Roofing

    The Resilience Task Force, working with the ERA staff, is also responding to the heightened interest in and concern over the resilience of the built environment by launching EpdmTheResilientRoof.org. The new website adds context to the information about EPDM products by providing a clearinghouse of sources about resilience, as well as an up-to-date roster of recent articles, blog posts, statements of professional organizations and other pertinent information about resilience.

    “This new website takes our commitment to the construction industry and to our customers to a new level. Our mission is to provide up-to-date science-based information about our products. Resilience is an emerging need, and we want to be the go-to source for architects, specifiers, building owners and contractors who want to ensure that their construction can withstand extreme events,” said Mike DuCharme, Chairman of ERA.

    EPDM roofs can be easily repaired and restored without the use of sophisticated, complicated equipment. Photo: Hutchinson Design Group.

    EPDM roofs can be easily repaired and restored without the use of sophisticated, complicated equipment. Photo: Hutchinson Design Group.

    EPDM and Resiliency

    The Resilience Task Force also conducted extensive fact finding to itemize the specific attributes of EPDM membrane that make it a uniquely valuable component of a resilient of a roofing system:

  • EPDM is a thermoset material with an inherit ability to recover and return to its original shape and performance after a severe weather event.
  • EPDM has been used in numerous projects in various geographic areas from the hottest climate in the Middle East to the freezing temperatures in Antarctica and Siberia.
  • After decades of exposures to extreme environmental conditions, EPDM membrane continues to exhibit a great ability to retain the physical properties and performances of ASTM specification standards.
  • EPDM is the only commercially available membrane that performs in an unreinforced state, making it very forgiving to large amounts of movement without damage and potentially more cycles before fatiguing.
  • EPDM offers excellent impact resistance to hail, particularly when aged.
  • EPDM is resistant to extreme UV exposure and heat.
  • EPDM far exceeded the test protocol ASTM D573 which requires materials to pass four weeks at 240 degrees Fahrenheit. EPDM black or white membranes passed 68 weeks at these high temperatures.
  • Exposed EPDM roof systems have been in service now for 50-plus years with little or no surface degradation.
  • EPDM is versatile.
  • EPDM can be configured in many roofing assemblies, including below-grade and between-slab applications.
  • EPDM is compatible with a broad range of construction materials/interfaces/conditions, making it a good choice for areas that may encounter unique challenges.
  • EPDM can be exposed to moisture and intense sunlight or totally immersed in salty water.
  • EPDM can easily be installed, repaired and restored following simple procedures without the use of sophisticated, complicated equipment.
  • EPDM can be repaired during power outages.
  • For further information about the need for resilience, and the appropriate use of EPDM in resilient structures, visit EPDMTheResilientRoof.com.

    Retrofit Roofing Project Highlights Advancements in Building Materials and Methods

    The roof was replaced on Huntsman Corporation’s Advanced Technology Center, an L-shaped, 70,000-square-foot facility housing expensive equipment and research labs. A TPO membrane roof system was installed over high-density polyiso cover board.

    The roof was replaced on Huntsman Corporation’s Advanced Technology Center, an L-shaped, 70,000-square-foot facility housing expensive equipment and research labs.

    Over the last few decades, computer and scientific innovations have evolved at a furious pace, with new technologies rapidly replacing only slightly older ones. In this race for the latest and greatest, it sometimes feels like the devices in our pockets and controlling our home stereos are from some virtual reality, while the building materials of our homes and workplaces are relics of a bygone age. But, looks can be deceiving, and the polyiso insulation industry is playing a role in evolving our built environment.

    For example, many commercial buildings seem only superficially different from those built a generation ago when seen from a distance. But, from behind the glass curtain walls and updated building amenities, we may not notice the disruptive technologies that have substantially improved building systems in recent years. Informed by sophisticated research and utilizing advanced components, cutting-edge building materials are thinner, stronger and more resilient than traditional products. Adopting them in both new construction and renovation can appreciably improve building performance, while also decreasing environmental impact. These products are particularly attractive to forward-looking companies interested in buildings that will prove cost-effective over the long term.

    A Case in Point

    When the Huntsman Corporation began considering facility improvements for its Huntsman Advanced Technology Center (HATC) in The Woodlands, Texas, they decided to embrace the most innovative materials available. This four-building campus, located about 35 miles north of Houston, serves as the company’s leading research and development facility in the Americas, so it is appropriate that it be built with products as advanced as the technology it houses. Replacing the aging PVC roof on Building 1 was a key element in this upgrade.

    After more than two decades of exposure to the Texas heat, the roof was approaching the end of its useful life. With expensive equipment and valuable research in labs throughout the building, Huntsman didn’t want to take any chances in modernizing the L-shaped, 70,000-square foot facility. With the added incentive of receiving the highest-level certification from its insurer, the company decided to remove and completely replace the existing roof with state-of-the-art materials.

    Commercial roofs in Texas are required to have an insulation R-value of 20 or higher, so simply replacing the existing membrane and lightweight insulating concrete on a metal deck that the building had used before with the same materials would not have sufficed. In addition, current codes which say that old roofs need to be brought up to current code when doing a tear-off job. After reviewing the options, they chose to install thermoplastic polyolefin (TPO) membrane roofing over high-density polyiso cover board.

    The polyiso cover boards are lightweight and easy to cut, which reduces both time and labor costs for installation. They add strength and protection to a roofing system, enhancing the system’s long-term performance. They can be shipped with approximately three times more square feet per truckload than gypsum products, so fewer trucks are needed, leading to fuel and transportation savings. Plus, they can be cut without specialized tools and workers don’t have to worry about the dust that is created when sawing, as they would with other types of cover boards. And most importantly, these high-density boards are based on proven technology.

    A TPO membrane roof system was installed over high-density polyiso cover board.

    A TPO membrane roof system was installed over high-density polyiso cover board.


    Drawn to polyiso for its high R-value per inch of thickness, compressive strength, impressive fire-, wind- and moisture-resistance, long-term durability, and low environmental impact, Huntsman partnered with roof mechanics experienced in working with these materials and committed to both safety and quality.

    If the original installers of the previous roof 22-years earlier had witnessed this new project, they would have been amazed. Instead of hoisting heavy materials up ladders, pallets are deposited on the roof by crane. Boards are attached with fasteners and plates or foam adhesives to the deck, and robotic welders seal the seams in the TPO membrane.

    The new roof is resistant to ultraviolet, ozone and chemical exposure, which contributes to a lifespan of more than 20 years, while being virtually maintenance-free. Workers who access the roof to remove debris from the tall trees on the HATC campus can easily stay on the safety-taped walk pad areas. The roof materials are all recyclable later, leading to a very low environmental impact.

    Increasing the thermal resistance to an impressive R-21 for the combined roof system, the building now exceeds local, state and international building codes. This added insulation and the reflective white surface of the new roof are going to lower energy consumption and lead to greater indoor comfort and a decreased load on HVAC systems. The roof is much less susceptible to the mold, mildew, and will help prevent water from pooling and ponding as it did on the old roof.

    A new commercial roof is a substantial investment. Luckily, with all the cost savings inherent in both the installation process and the whole-life use of high-density polyiso cover boards, companies don’t have to forego state-of-the-art materials for financial reasons. Factoring in the ease of installation (from cutting to less dust) and weight of the cover boards, retrofitting an older building with updated roof systems can be a win-win for both clients and crews.

    PHOTOS: HUNTSMAN CORPORATION