The team at the Center for Offsite Construction is excited to share that we've reached important milestone in the development of CfOC-ICC-1220, the proposed standard for utility interfaces between off-site constructed products and host buildings.

The current (v0.2) working draft marks the moment when 1220 becomes navigable as a standard. Earlier versions helped define the problem: off-site construction needs repeatable, inspectable, and reliable interface conditions so that pods, modules, and modular components can be coordinated with host buildings before every project becomes a bespoke coordination exercise. This new version gives the consensus committee (and the public) a working structure for moving from general interface concepts toward specific, prescriptive technical requirements.

Too often, standards work can easily become abstract. A committee can agree that “coordination” is important while still leaving each project team to decide, late in design or construction, where interfaces go, how much space is required around them, how workers and inspectors reach them, and how the final connection is tested and accepted. CfOC-ICC-1220 is intended to push past that ambiguity. Its purpose is to establish the technical conditions that allow off-site constructed products to be designed, manufactured, delivered, connected, inspected, and accepted with greater confidence.

This draft gives every industry stakeholder a clear way to read, test, and improve the standard. It is intentionally scaffolded for expansion and detail. Some provisions are ready for technical review. Others are reserved for future committee decisions. But those reserved sections are not empty spaces: these are decision spaces. They mark where the committee must now determine which interface locations, ratings, clearances, access conditions, and verification requirements should become repeatable industry expectations.

A standard organized around the interface

CfOC-ICC-1220 is designed to operate within the broader family of off-site construction codes, standards, and guidelines, including: 

• ICC/MBI Standard 1200 (2021),
• ICC/MBI Standard 1205 (2021),
• ICC/MBI Standard 1210 (2023),
• ICC Guideline 6 (2023),
• and related documents.

The draft does not attempt to duplicate the work achived in those documents. 1220 uses them as the surrounding framework for construction, inspection, approval, and regulatory administration, while focusing on a narrower and more specific problem: the interface conditions required for repeatable off-site construction.

That focus shapes the definition strategy. The draft assumes that many general terms already exist in ICC/MBI 1200, 1205, and 1210. Rather than rewriting those definitions, Chapter 2 adds vocabulary needed for interface work. Important terms include Interface, Pod, Host Building, Connection, Accessible Interface, Interface Location, Interface Tolerance, Interface Type, Service Rating, and Verifiable Interface.

This is way of focusing the committee’s precious attention. The standard is has grown organized around the interface: where it is located, how it is connected, how much space is required around it, how it remains accessible, how it is protected, and how it is inspected, tested, and accepted.

Three layers of the draft

The current draft is organized in three major layers.

The first layer, Chapters 1 through 4, establishes the general framework. Chapter 1 addresses application and administration. Chapter 2 establishes definitions. Chapter 3 introduces modular dimensional coordination. Chapter 4 sets up the general interface requirements that later chapters apply to specific building systems.

The second layer, Chapters 5 through 8, applies that general framework to building systems. Chapter 5 addresses plumbing interfaces. Chapter 6 addresses mechanical interfaces. Chapter 7 addresses electrical interfaces. Chapter 8 is reserved for fire and life safety interfaces, with the current working assumption that those systems may remain outside the first edition unless the committee determines they must be included.

The third layer, Chapter 9, establishes the logic for testing, inspection, verification, energization where applicable, records, and acceptance. This chapter is especially important because an interface has two sides: the host-building side and the off-site constructed product side. Those two sides may be produced by different parties, in different locations, and in different sequences.

Together, these layers give the committee a way to move from general principles to system-specific requirements and then to verification.

Location, clearance, and access

One of the most important contributions of the current draft is its separation of three concepts that are often conflated during project coordination: location, clearance, and access.

Location refers to where the interface is placed. In the draft, location is intended to become a repeatable requirement wherever possible. Future committee work will determine where plumbing, mechanical, electrical, and other interfaces should be located in relation to pods, modules, modular components, host buildings, reference planes, datums, finished floor elevations, structural grids, edges, and other reference points.

Clearance refers to the three-dimensional space around the interface that must remain available for connection, inspection, testing, maintenance, repair, replacement, energization where applicable, and acceptance. A connection is of limited value if it exists physically but cannot be reached by tools, inspected by an approved party, or safely serviced after installation.

Access refers to how a worker, inspector, or other authorized party reaches the clearance zone. Access may be provided by an access panel, removable panel, hatch, door, or other approved opening. Access is related to clearance, but it is not the same thing. The clearance zone is the work area. The access opening is the route into that work area.

Chapter 4 is organized around this distinction. Section 402 addresses interface locations. Section 403 addresses interface clearance zones. Section 404 addresses access to interface clearance zones. That structure then repeats in the system-specific chapters, allowing plumbing, mechanical, electrical, and other systems to add their own requirements without losing the overall logic of the standard.

For committee members, this organization turns broad coordination questions into a repeatable sequence of technical questions. For each interface, the committee can ask: Where is it located? What clearance zone is required around it? How does a worker or inspector reach that zone? How is the interface protected before and after connection? How is it inspected, tested, and accepted?

Chapter 5: plumbing interfaces

Chapter 5 applies the standard’s general interface logic to plumbing. It governs interfaces where water supply, drain, waste, vent, condensate, or other plumbing systems are connected, extended, transferred, supported, protected, or coordinated across an interface.

The chapter begins by defining the plumbing interface as the designated connection between the host building and the off-site constructed product. It then frames compatibility as a two-sided requirement: the host building must provide a corresponding plumbing interface, and the off-site constructed product must provide a compatible interface on its side. The chapter also introduces the need for standard plumbing interface types, including connection type, pipe size, material compatibility, flow direction, pressure or drainage condition, slope requirements, and other characteristics necessary to establish compatibility.

The chapter then addresses water supply, drain and waste, vent, and condensate interfaces. It also includes provisions for preventing improper connections and identifying plumbing interfaces. Section 502 reserves space for prescribed plumbing interface locations, plumbing clearance zones, plumbing access requirements, and protection requirements. These reserved sections will become the committee’s decision points.

Chapter 6: mechanical interfaces

Chapter 6 applies the same structure to mechanical systems. It governs interfaces involving ductwork, ventilation, exhaust, outside air, hydronic piping, refrigerant piping, condensate piping, combustion air, and related mechanical systems.

The draft currently emphasizes ductwork, ventilation, exhaust, and outside air interfaces, while several mechanical piping categories are marked “not used” for now. This is a useful example of the draft’s scaffolded structure. The chapter can support a broader range of mechanical interface requirements over time, but the first edition may focus on the systems the committee determines are ready for standardization.

Mechanical interfaces are treated as rated, identifiable, protected, accessible, inspectable, and testable conditions. The chapter addresses interface types, host-building-side compatibility, off-site-product-side compatibility, duct sealing, flexible connections, balancing and testing access, mechanical piping verification, and records. Like Chapter 5, it reserves space for prescribed interface locations, clearance zones, and access requirements.

Chapter 7: electrical interfaces

Chapter 7 focuses on electrical service interfaces. It currently frames the electrical service interface as a single designated connection between the host building and the off-site constructed pod, module, or modular component.

This “single service interface” concept is important because it simplifies the interface boundary. Internal distribution, branch circuiting, controls, low-voltage systems, step-down equipment, and related internal arrangements remain within the approved design of the off-site constructed product. The standard’s concern is the designated electrical service interface between that product and the host building.

The chapter addresses standard service ratings, compatibility between the host-building side and off-site-product side, acceptable electrical connections, grounding and bonding, disconnecting means, isolation, identification, location, clearance, access, and protection. It also reserves space for future prescribed electrical service interface locations and clearance requirements.

Chapter 8: fire and life safety interfaces

Chapter 8 is reserved for fire and life safety interfaces (which the committee has not yet affirmed the scope). The current draft leaves this chapter largely undeveloped. The work ahead will involve one of the most important standards-development questions: should the first edition of 1220 include fire and life safety interfaces, or should it focus first on plumbing, mechanical, and electrical utility interfaces? We're not sure how deeply this disciple complicates adoption. More to research!

By reserving the chapter, the draft gives the committee a place to make that decision without forcing the issue prematurely.

Chapter 9: sequence-neutral testing, inspection, and acceptance

Chapter 9 is the draft’s most important procedural innovation. It recognizes that an interface has two sides: the host-building side and the off-site constructed product side.

On one project, the host-building side may be completed first by site trades. On another, the off-site constructed product side may be completed first in the factory. In other cases, both sides may be completed independently and brought together later. The standard cannot assume a single order of operations.

Chapter 9 therefore uses a sequence-neutral structure. It allows either side of the interface to be verified for readiness before the other side is complete. Then it requires verification when the two sides are mated, verification after the completed connection is made, and final acceptance after required inspection, testing, energization where applicable, concealment verification where applicable, and records are complete.

The core stages are:

Interface-side readiness. Each side of the interface can be checked independently for location, service rating, protection, identification, clearance, access, and compatibility.

Mating verification. When the host-building side and off-site constructed product side are brought into their intended relationship, the interface can be checked for alignment, fit, access, protection, and readiness for final connection.

Connection verification. After connection, the completed interface can be checked for proper joining, fastening, sealing, continuity, support, access, testing status, and system-specific requirements.

Acceptance. The completed interface can be accepted only after the necessary readiness verification, mating verification, connection verification, testing, energization where applicable, concealment verification where applicable, and records have been completed.

Followers of the CfOC know that Handshake work is deeply studying these steps in a legal context. The tie-in to (offsite focused) standard forms of agreement is key… so this standard structure preserves flexibility in construction sequencing without returning the industry to project-specific interface design. The sequence may vary. The interface requirements should become reliable.

Building Strong Bridges between 1220 and other CfOC Work Products

CfOC-ICC-1220 is one part of a larger research roadmap at the Center for Offsite Construction.

The standard connects directly to the CfOC’s work on the CTO file type and the emerging CTO Interface Standard. A configurator file type can describe product options, constraints, and compatibility rules, but physical interfaces still need standard definitions. Machine-readable coordination becomes more powerful when it points to repeatable real-world interface requirements.

The standard also connects to Handshake, the CfOC’s work on new standard forms of agreement for offsite construction. If off-site constructed products are to be bought, delivered, inspected, accepted, and paid for more like repeatable products, then the industry needs clearer technical acceptance points. Chapter 9’s readiness, mating, connection, testing, records, and acceptance framework helps supply that technical backbone.

Finally, 1220 connects naturally to the future development of CfOC-ICC-1230, which is expected to address panel-to-panel and panel-to-structure interfaces. Together, these efforts begin to describe a broader interface infrastructure for offsite construction: pods, modules, modular components, panels, host buildings, and the technical boundaries between them.

The current version of CfOC-ICC-1220 is an achievement that it now organizes the questions in the right places. It gives the committee a careful, rational, and repeatable framework for writing the technical requirements that follow.

That synthesis is what will drive the CTO marketplaces and an organized response to the affordable housing challenges that face our communities. It's a big step to not only have a working draft, and also a navigable standard for collaborators across North America.