The Upton Residences is one of the tallest buildings under construction in Denver, bringing 461 condo units and two conjoined towers to a downtown corner.
But just as it nears completion at Welton and 18th streets, it’s grabbing attention for another reason: claims that a subcontractor’s behavior put the entire structure at risk.
The project’s developer, Amacon, claimed in court filings that a concrete subcontractor, GCon, removed a temporary support system from a floor of the project, leading to cracking. If the contractor had continued to remove materials, the lawsuit states, the “consequences of an unsupported structure may result in further cracks and potential collapse of the structure.”
But the builder is tempering those dire warnings. In a statement to local media, Amacon said the project “remains a safe, secure, and successful development." The company’s structural engineer and a third-party firm have both “confirmed there is no risk whatsoever to the safety of workers, residents, or the public,” an executive said.
Meanwhile, a judge agreed to temporarily ban GCon from the construction site.
A concrete argument
The legal battle started with a dispute between Amacon and GCon over allegedly defective work, according to Amacon’s legal complaint. BusinessDen first reported on the dispute.
GCon had worked on the project since 2022. In May 2025, the subcontractor said Amacon owed it money, threatening to stop work “if payment wasn’t made in full,” the lawsuit states. Amacon responded that GCon’s work had “major deficiencies,” such as inconsistent planes and concrete that didn’t reach “contractual tolerances.”
Soon after, GCon corrected some of the reported errors but otherwise halted all work, per the lawsuit. The two parties continued to argue about GCon’s work for weeks. On July 11, Amacon demanded that the subcontractor provide “adequate written assurance” that it would finish pouring concrete on the rest of the project.
On July 14, Amazon declared GCon was in breach of the contract, with the developer saying it would hire other contractors to finish the work and charge GCon for the costs.
On Aug. 4, the lawsuit states, GCon “started removing materials and equipment from the Project site without the prior knowledge or approval of Amacon[.]”
That included bracing for concrete forms that Amacon had planned to pour the next day. But “[m]ost significantly,” Gcon allegedly removed the “reshore” from various points on and beneath level 39, near the top of the tower.
The reshore is “the temporary support system placed beneath a concrete slab or other structural element after the initial formwork and shoring have been removed. In essence, the reshore is meant to ensure structural stability,” the lawsuit states. “In essence, the reshore is meant to ensure structural stability. GCon’s unauthorized removal of reshore and bracing on and below level 39, which is now causing cracks to the concrete slabs on level 38 as it is overloaded, bearing the weight of both level 38 and 39.”
In a court hearing, GCon’s attorney rejected the idea that the subcontractor had sneaked off with the materials.
“They were removed not in the dead of night or without notice or an opportunity for Amacon to observe what was happening, but in fact in coordination with Amacon’s local representatives,” attorney Ryan Williams said at the hearing, according to BusinessDen.
Williams argued that GCon owns the materials and is also unhappy about accruing debt for equipment rental, BusinessDen reported.
The contractor also allegedly removed the shoring for the project’s concrete pumping system, though GCon both denied doing so and stated that the reshores were its property, the lawsuit states. Amacon then fired GCon from the job and alleges that its new contractor found more issues with the concrete work
GCon continued to argue that it had the right to enter the project site and retrieve its materials, work and equipment, per the lawsuit, GCon stated that it intended to remove all of its reshores, Amacon alleged.
The case is still ongoing.
Amacon is seeking at least $10 million in damages. While it won a preliminary injunction banning GCon from the site, the broader lawsuit could take longer to play out. GCon’s original contract was for about $16 million of work.
The suspension of work has already caused a 10-week delay in the project, according to Amacon. It’s scheduled to open early in 2026.
It’s set to be Denver’s largest condo project since 2009. Condos are for sale now, starting at $365,000.
Amacon did not immediately respond to a request for comment. GCon’s lawyer declined to comment.
