Lightweight Block, Heavyweight Benefits: At the Maryland Science Center, 24-inch-long lightweight concrete masonry units paid for themselves by saving masons half the labor

By Laura Drotleff and Don Eberly

Four newly constructed warehouses at the Maryland Science Center in Baltimore are close to being move-in ready, and two more are in progress. Built by St. John Properties, the buildings provided the center with a distinct advantage, both in the way they were constructed and the resources used – time, labor and materials. The project, started last March, called for six new warehouse buildings to be constructed on a section of the property approximately 300 yards from existing buildings. The warehouses were to be rented out for storage to a high-profile tenant with a strict timeline. The buildings had to go up quickly to fill the demand.

Knowing that constructing such a large project in an expedited situation would come with its share of budget concerns, the contractor for St. Johns Properties turned a local block, masonry and hardscaping supply company, for a solution. As a manufacturer of normal weight and lightweight concrete masonry units, the block producer knew that lightweight concrete masonry units would fill the need for a fast turnaround in construction, while staying within the project’s budget. The units contain ESCS lightweight aggregate, which makes them lighter and ultimately reduces labor and time in construction. “Lightweight block increases productivity even at the same labor pace, and workers are typically more efficient because the lighter block is less work intensive,” the producer says.

Get In, Get Out

As a result, the contractor used 24-inch-long lightweight concrete masonry units in place of the standard weight 16-inch gray units. In doing so, he reduced construction time and labor specific to this part of the project by 50 percent. In all, 6,600 24-inch-long lightweight units were used for the straight walls and corridors of each of the four 75,000-square-foot buildings at the Maryland Science Center. The mason also used several 12-inch lightweight units and a variety of normal weight material for other applications within the job.

Using lightweight block worked within the building’s budget, the mason found, and he benefited from using this alternative in several ways. In addition to getting paid by the square foot, he also made money for completing the job faster, and his crew was better off for using lighter weight units and avoiding common injuries associated with heavier block.

According to Jeff Speck, vice president of sales and marketing at Big River Industries, Inc., these are the key benefits of using lightweight masonry units, especially in large jobs like warehouse construction. “The lightweight factor helps contractors complete projects sooner so they can generate revenue from the projects earlier, which is better for the property owners as well,” says Speck. “In construction, we all know time is money, and if property owners can reduce the number of days it takes to construct a building, it helps them project when it can be rented and begin earning revenue.”

What Makes Lightweight Units Lighter?

The lightweight units used for the buildings contain 60 percent ESCS, by volume, 28 percent natural aggregates, and the rest is cement and water. The finest gradation of ESCS lightweight aggregate (LWA) qualifies as a reclaimed material, which is a benefit for contractors applying for Leadership in Energy and Environmental Design (LEED) credits.

The quality of ESCS LWA results from a carefully controlled manufacturing process. In a rotary kiln, selectively mined shale, clay or slate is fired in excess of 2000 degrees F. The raw material expands, cools, and is then processed to specified grading. The result is a high-quality, lightweight aggregate that is inert, durable, tough, stable, highly insulative, and free-draining, ready to meet stringent structural specifications.

Familiarizing with the process by studying ESCSI’s SmartWall units, the block producer developed its own brand-name block to provide customers like St. John Properties with a unique approach to time-, labor- and cost-savings. “The lightweight units have better thermal properties, saving property owners money on heating and cooling,” Speck says. “Additionally, they have superior fire resistance, providing more structural stability, which is an improvement over regular weight material; and, they’re safer to handle

Productivity Is Critical

Despite all the benefits using lightweight block offers, most construction projects are ruled by the budget and the bottom line, according to the block producer. “Even though it makes complete sense to use a lighter weight option, it is tough to persuade some architects and contractors to do it because of the upfront price tag of the units,” he says. “But, the savings is realized in the end, because more important than the cost of the units is the cost of the wall.”

In masonry construction, the cost of labor has exploded, with legal labor in the $13 per hour range and up. Inflation rates cause contractors to refrain from spending more for materials. “But, with labor costing at least 50 percent of many masonry unit projects, the 50 percent labor savings attainable by using 24-inch-long lightweight units will more than pay for the additional upfront product cost,” the producer says. “Block is only 10 percent of what makes up many masonry contracts. If you’ve got a $2 million project, the cost of the block could be approximately $200,000. Labor makes up 50 percent of the costs. If you can take a variable cost like that and improve it, the overall cost of the project will go down.”

In the case of the Maryland Science Center warehouses, the mason was handling 24-inch-long units, which weigh the equivalent of 16-inch-long normal weight units. He gained 50 percent more wall area by placing the same number of units, at the same labor pace. To assist in pre-planning the upfront product costs versus ROI, the producer provided detailed spreadsheets to the project planners, providing line item descriptions for the costs and savings they would realize by using the lightweight alternative. From there, he worked with the Maryland Science Center warehouse project team on a strategy to keep costs aligned with the budget.

Safety and Savings Hand-in-Hand

According to Speck, aside from the 50 percent labor savings that the 24-inch-long lightweight units can provide, using them also takes safety programs and corporate accountability to another level. “If employers treat masons well, as the productive members of the company who they are, using lightweight block is a long-term investment in the ethical treatment of employees,” he says.

By thinking in terms of money that can be saved from having fewer injuries and workers’ compensation claims, contractors stand the chance of decreasing signifciant relational costs of projects. “A contractor once told me that one back injury costs his company more money than the difference in price of normal weight block versus lightweight block. That savings would buy lightweight block for two years,” says Speck.

When it comes to initial product selections, preliminary costs, and the possible eventual outcomes surrounding masonry projects such as this one, thinking long-term might very well yield the highest level of profitability. 

Readers’ Resources:

Visit  to learn more about ESCS LWA and SmartWall lightweight concrete masonry.

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