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Project Profile: Mission Gorge / Decena Apartments

Project Profile: Mission Gorge / Decena Apartments

Project Overview

ISE Structural Engineers provided structural engineering services for the Mission Gorge / Decena Apartments, a five-story Type II modular residential development in San Diego. Designed and built in collaboration with Impact Housing, LLC, this large-scale project showcases the efficiency and scalability of off-site modular construction.

Project Type: Multifamily Residential

Location: 6171 Mission Gorge Rd., San Diego, CA

Services Provided: Structural design for modular construction based on 515 modules and a concrete slab-on-grade foundation system.

Engineering for California’s Largest Modular Multifamily Project to Date

The Mission Gorge / Decena Apartments project represents a major milestone in large-scale modular housing. Developed with Impact Housing, the five-story residential building delivers 485 units across more than 371,000 square feet using off-site modular construction. At the time of construction, the development is believed to be the largest privately funded modular apartment building in California.

Impact Housing began setting modules on December 8, 2025, and completed installation on January 31, 2026—an aggressive schedule that underscores the advantages of well-coordinated modular execution.

Engineering Approach

One of the standout features of this project was the repetitiveness and consistency of Impact Housing’s module design. From a structural engineering standpoint, that consistency streamlined connection detailing and improved overall design efficiency.

Consistent module-to-module connections allowed ISE to:

  • Standardize connection details
  • Improve coordination with factory production
  • Support rapid module placement in the field
  • Reduce potential variability during erection

Because the structural interfaces were repeatable, module setting proceeded at an impressive pace, with multiple modules installed per day.

The decena project is believed to be the largest modular multifamily project in California consisting of 515 modules and a concrete slab-on-grade foundation system.

Solving Structural Challenges

A key technical challenge involved developing embed plates within the slab-on-grade system to anchor holdowns. Proper placement and coordination of embed plates is critical in modular construction, where precision in anchorage directly impacts module alignment, vertical load transfer, and lateral resistance.

ISE worked through detailed coordination and design refinement to ensure:

  • Accurate embed plate placement within the slab
  • Proper anchorage for holdown systems
  • Alignment with factory-produced module geometry
  • Efficient installation sequencing in the field

These coordination efforts were essential to maintaining the accelerated module-setting schedule.

Modular Expertise in Action

Modular construction introduces a different set of engineering considerations than traditional site-built projects, particularly when it comes to construction sequencing. Because modules are fabricated off-site and assembled in a precise order once they arrive on-site, the structural design must account for how the building will actually be erected. Without careful planning, it is possible to create conditions where certain modules cannot be installed because earlier placements restrict access or structural connections.

ISE’s experience with modular design allowed the team to approach the project with sequencing in mind from the start. Structural systems were coordinated to ensure load paths remained continuous as modules were stacked and connected, while also accommodating crane placement and installation logistics. By designing the structure with the realities of factory production and field assembly in mind, ISE helped ensure that the building could move efficiently from fabrication to final assembly without delays or conflicts during installation.

Results

The Mission Gorge / Decena project demonstrates how thoughtful structural engineering, factory repetition, and field coordination can combine to deliver large-scale housing efficiently.

  • 515 modules installed in just under two months
  • 371,631 SF of modular residential space
  • 485 residential units delivered through off-site construction
  • Opening planned for February 2027

For ISE Structural Engineers, the Decena Apartments project reflects the firm’s continued leadership in modular and multi-family structural design—combining technical precision, sequencing expertise, and collaborative coordination to deliver complex projects at scale.