Arcosa’s Lightweight Aggregate Elevates Costco Wholesale Headquarters Campus
Key Insights:
Quick Facts:
- Name: Costco Wholesale Headquarters
- Location: Issaquah, WA
- Customer: Ferguson Construction Inc.
- Client: Costco Wholesale
- Size: Eight-level parking structure with 290 additional spaces
Challenge: Expand an already under-construction parking structure from seven levels to eight, using post-tensioned concrete, without altering the original foundation.
How Arcosa Helped
- Our Solution: Arcosa provided lightweight aggregate that allowed the parking deck to expand mid-construction by reducing the overall weight of the structure, enabling the addition of an eighth level without changing the foundation.
- Why Lightweight Works: Lightweight aggregate enabled the use of post-tensioned concrete on the top three levels, a unique approach in the Northwest, making the structure lighter without compromising strength.
Final Results
- The modified design resulted in a successful eight-level parking structure, with the use of lightweight post-tensioned concrete helping achieve early target strengths for the upper levels and reducing the weight on the foundation
Key Quote
“Using lightweight, post-tensioned concrete on the last three levels of the parking structure allowed us to go from seven to eight levels on the original foundation.” – Tom Whiteman, Vice President of Sales and Marketing, Ferguson Construction Inc.
Context:
- Considerations: The use of lightweight concrete in post-tensioning is rare in the Pacific Northwest, but it proved critical for expanding the parking structure at the Costco headquarters without significant alterations to the original design.
- Lesson to Learn: Consistency in the mix, workability, and meeting early target strengths are key when using lightweight concrete in post-tensioning applications.
Explore Further
Learn more about Arcosa Lightweight’s solutions for improving construction efficiency and enabling mid-project design modifications.
Arcosa’s Lightweight Aggregate Elevates Costco Wholesale Headquarters Campus
When Costco decided to add an eighth level and 290 additional parking spaces to the original parking structure at their headquarters in Issaquah, WA—while the structure was already designed and under construction—Arcosa Lightweight provided the solution. The parking deck, which had been planned as a seven-level structure, was able to be modified mid-construction to accommodate the extra level thanks to Arcosa’s lightweight aggregate.
At the time, Costco was struggling to fit within its limited campus footprint, forcing the company to maximize the use of space within its existing boundaries. The successful use of Arcosa’s lightweight aggregate allowed the additional parking level to be built without significant changes to the foundation, supporting the growing demands on parking infrastructure.
Paving the Way for Campus Expansion
Since then, Costco has received the necessary land use approval from the City of Issaquah to proceed with a long-awaited 1.2-million-square-foot expansion of the Costco Wholesale Headquarters Campus. This expansion includes a new 10-story parking structure and a nine-story office building, designed to consolidate thousands of employees from surrounding leased properties back onto the main campus.
The successful implementation of lightweight construction materials in the original parking structure laid the groundwork for this broader campus expansion, demonstrating the value of Arcosa’s lightweight aggregate in managing space and structural efficiency.
Lightweight Post-Tensioned Concrete Unique in the Northwest
“Using lightweight, post-tensioned concrete on the last three levels of the parking structure allowed us to go from seven to eight levels on the original foundation,” explains Tom Whiteman, Vice President of Sales and Marketing at Ferguson Construction Inc.. He adds that the use of lightweight concrete in a post-tensioning application is somewhat unique in the Northwest.
Post-tensioning involves the placement of prestressing steel cables, or tendons, inside plastic ducts or sleeves in the forms before the concrete is placed. Once the concrete has gained strength, but before service loads are applied, the cables are pulled tight, or tensioned, and anchored against the outer edges, providing reinforcement.
“A consistent mix and workable slump are keys to making lightweight concrete work in a post-tensioning system,” Whiteman said, adding that “early target strengths have to be achieved before post-tensioning can occur.”
Ready Mix producer Cadman Inc., a company that has been supplying concrete in the Puget Sound region for over 75 years, was supplier for this project. “Our slumps were dialed in from the start and we exceeded our strength requirement for 3-day stressing,” Whiteman says.
This early use of innovative construction techniques at Costco’s campus helped address immediate parking needs while setting the stage for the broader expansion.
Future Outlook
The original parking structure project marked the beginning of Costco’s strategy to scale its headquarters infrastructure to accommodate long-term growth. Today, as the Costco Wholesale Headquarters Campus undergoes a transformative expansion, the innovative solutions provided by Arcosa Lightweight continue to play a pivotal role in ensuring that the company can meet its operational and workforce needs in a sustainable, efficient manner.
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