By Thomas Renner
The Virginia Department of Transportation (VDOT) faced a complicated roofing problem at its hazardous chemical storage building in Cross Junction, where it stores salt and de-icing products to help keep roadways clear during dangerous winter conditions.
Architect and project engineer Gauther Alvarado Associates designed an innovative hybrid solution that is creative, cost-efficient, and expected to provide decades of service, meeting the most critical requirements of the state agency.
“Since this is a government project, longevity was a priority,’’ said Stephanie Stein, the lead architect on the project for Gauther Alvarado. “As a result, any surface that comes into direct contact with the salt needed to be corrosion resistant to increase the lifespan of the building in this extremely corrosive environment. “
Corrosion From Salt
While salt that is spread on roadways helps drivers, its impact on building materials is less desirable.
When Dinks Construction started the project, workers found issues with decay in some concrete walls caused by salt corrosion. Teams tore out a portion of the wall and rebuilt it before replacing the roof.
Salts remove moisture from an environment, causing a hygroscopic reaction. The mineral retains water, which then promotes condensation. The water absorption allows corrosion to occur at lower humidity and for longer periods than otherwise expected. Salt also increases water’s ability to carry current and speeds up the corrosion process.
As the building ages and the overall salt content of the building increases, the building fabric tends to become damper over time. When the wet salt dries out, it crystalizes and expands, creating pressure that over time breaks down the building fabric. Crumbling, spalling, flaking, and cracking of the building fabric is largely related to the crystallization of salts.
That breakdown over time is precisely what happened at the VDOT facility in Cross Junction, especially in the roofing materials. Salt is the primary ingredient stored in the building to help VDOT keep the roads clear. Anti-icing, de-icing, and snowmelt products, all of which contain salt, are also stored at the facility.
“In the early fall, salt is loaded into the building through three roof hatches accessible from the upper part of the site,” Stein said. “During the winter, the salt stored in the building’s three bays is accessed on the lower part of the site as needed, in response to snow events.”
The hybrid solution included replacing the roof hatches and installing a liner on the hatch. The liner, which was installed by Rhino Linings of Winchester, VA, is similar to the lining on truck beds. The spray-on material protects against corrosion while also providing abrasion, impact and chemical resistance.
The roof hatches were custom-made by BILCO. Architects selected three aluminum models, each 3-feet, 11-inches wide and 11 feet long. They include Type 316L stainless steel hardware, which is the most corrosion-resistant type of stainless steel. As another layer of protection, the roof hatch curbs were coated in an asphalt-based liquid coating that will help concrete inside the building withstand the corrosive nature of salt. BILCO manufactures a stainless steel roof hatch, but the aluminum hatch with the protective lining saved money for VDOT.
“With this solution, we combined the durability associated with the BILCO pre-manufactured aluminum roof hatches with the corrosion-resistant properties of the truck bed liner,” Stein said.
Dinks’ workers installed the roof hatches while Don Largent Roofing installed EPDM, a durable, synthetic membrane, on the remainder of the roof. The roof hatches with the unique liner applied and the EPDM roofing material is expected to extend the roof’s durability up to 35 years.
Project At A Glance
- Where: Cross Junction, VA
- What: A hazardous chemical storage building owned by the Virginia Department of Transportation
- Problem: Salt stored in the facility, which is used to help maintain roadways in snow and ice conditions, caused corrosion on roofing materials.
- Solution: Gauther Alavarado Associates, the architect, used three custom-made aluminum roof hatches from BILCO. Workers installed a spray-on line, similar to those used on truck beds, to protect against corrosion. Roofers installed an EPDM material. The hybrid solution with the hatches, liner, and roofing material is expected to extend the roof’s durability up to 35 years.
- Fast Fact: Salt is a building material enemy. The material retains water, which then leads to condensation. The building fabric becomes damper over time, and when salt dries, it crystalizes and expands, creating pressure that over time breaks down the building fabric.
Architects could have constructed the building without the roof hatches. The building, however, is located on a hill in the Cross Junction, which is located in northern Virginia and near the border of West Virginia. Accessing the facility is challenging, and architects sought a design that provided a driver-friendly solution for pickup and delivery.
With the roof hatch design, VDOT workers can simply open the hatches and delivery drivers can drop off loads of salt through the hatches. The system eliminates the need for salt to be moved into the facility via front-end loaders or some other means of conveyance. The drop-and-go solution is also environmentally-friendly, as the salt is permanently stored in one place until it is needed for the state’s roadways.
Dumping salt through the open hatch doors, however, could have impacted the structural integrity of the hatches. “One of our prime concerns during the design phase was the additional force exerted on to the roof hatches during salt loading operations,” Stein said.
GAA’s structural engineers designed a structural steel bumper to provide additional support to the roof hatch. When the hatches are open prior to loading the building with salt, the roof hatch covers rest upon the bumpers.
“The additional force applied to the roof hatch covers during the salt loading is then directly transferred to the steel bumpers to protect the structural integrity of the roof hatches,” Stein said.
An early February snowstorm dumped eight inches of snow in Cross Junction. Historically, the area only receives about 19 inches a year. It is not, by any standard, in the snow belt of the United States.
It is, however, located closely to highly-traveled Interstate 81, a major north-south thoroughfare that rolls on into Maryland and Pennsylvania in the north and southern Virginia and Tennessee. More than 100,000 tons of freight travel along I-81 each day, according to Roanoke.com, and trucks account for more than 23 percent of the road’s traffic. That is a higher percentage than any other major road in the state.
While the road is considered among one of the safest in the state, any interstate with fast-moving traffic can become deadly, especially in bad weather conditions. While the hazardous storage building in Cross Junction might not be a well-publicized project, its impact and importance for the region’s drivers is huge.
The design and construction in this project required creativity and ingenuity in solving some unique challenges. Every facility is different and require individual solutions, but the Cross Junction project posed extraordinary questions that architects rarely see.
“This was a fun project because it was quite different,” Stein said. “This was our second roof and roof hatch system that we designed for VDOT. We had the opportunity to incorporate a few lessons learned from the first roof system replacement. It is our hope that we will continue to adapt this roof system prototype for additional VDOT sites in the future.”
Thomas Renner writes on building, construction, engineering and other trade industry topics for publications throughout the United States.