Same Codes, Different Paths: How Approvals Really Differ for Modular and Site-Built Homes

 

Ask almost any builder whether approvals are getting harder, and the answer is usually an immediate “yes.” Ask a modular factory owner the same question, and the response is often followed by a sigh, a story, and a warning label.

At first glance, the approval process for new homes—whether built onsite or in a factory—should be straightforward. In theory, they are governed by the same building codes, reviewed by the same authorities, and expected to deliver the same outcomes: safe, durable, code-compliant housing.

In practice, however, the approval pathways for modular and site-built homes differ in ways that shape timelines, risk, cost, and perception. Neither path is inherently easier or harder in every jurisdiction, but they are undeniably different—and those differences matter.

The Myth of “Different Codes”

One of the most persistent misconceptions in housing is that modular homes are built to a “different” or “lower” code than site-built homes. For permanent modular housing, that simply isn’t true.

Both modular and site-built homes must comply with the same adopted local or state building codes, typically based on the International Residential Code (IRC) or International Building Code (IBC). Life-safety standards, energy requirements, structural loads, fire resistance, and accessibility rules apply equally.

The difference is not what code applies, but how compliance is reviewed, verified, and approved.

Site-Built Homes: Familiar, Visible, Incremental

For traditional onsite construction, the approval process follows a pattern that regulators have used for decades.

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Plans are submitted to the local authority having jurisdiction (AHJ). Once approved, construction proceeds in phases, with inspectors visiting the site at defined milestones—foundation, framing, mechanicals, insulation, and final occupancy.

This process has three advantages:

• Inspectors can see work as it happens.
• Corrections can be made incrementally.
• The approval authority retains continuous, direct oversight.

Because this method is familiar, most building departments are comfortable with it—even when projects are complex. Delays still happen, but they are usually tied to staffing shortages, workload backlogs, or incomplete submissions rather than structural confusion about the process itself.

Modular Homes: Same Standards, Split Oversight

Modular construction introduces a different approval structure, even though the finished home must meet the same code.

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Instead of all inspections happening onsite, a significant portion of compliance verification occurs in the factory, often under a state modular program or through approved third-party inspection agencies. Modules may be inspected, certified, and sealed before they ever leave the production line.

Local inspectors typically retain authority over:

• Foundations
• Site work
• Utility connections
• Set and finish work
• Final occupancy

This split oversight model is efficient in theory—but in practice, it introduces complexity.

Where Modular Approvals Often Get Complicated

The challenge with modular approvals isn’t stricter standards; it’s coordination and confidence.

Local officials sometimes struggle with:

• Reviewing construction they can’t physically observe
• Interpreting factory inspection reports
• Understanding which agency is responsible for what
• Accepting certifications they don’t encounter frequently

In jurisdictions with established modular programs, these issues are largely resolved. In areas with limited modular experience, however, the learning curve can be steep, leading to additional documentation requests, longer reviews, or conservative interpretations of authority.

None of this is malicious. Most regulators are trying to manage risk with limited resources. But from the builder’s perspective, the result can feel like a higher barrier to entry.

Are Modular Homes Favored Anywhere?

In some regions, yes—quietly and pragmatically.

States or cities facing acute housing shortages, disaster recovery demands, or labor constraints have begun streamlining modular approvals. In these jurisdictions, modular projects may benefit from:

• Pre-approved factory designs
• Expedited plan review
• Clear division of inspection responsibility
• Faster issuance of certificates of occupancy once set

These advantages are not about favoritism; they are about predictability and throughput. When regulators understand modular systems well, approvals can actually move faster than traditional site-built projects.

The Risk Profile Is Different

One reason approvals feel heavier for modular projects is that the risk profile is front-loaded.

With site-built homes, issues can often be corrected mid-stream. With modular homes, most of the structure is completed before it arrives onsite. Mistakes discovered late can be expensive and difficult to fix.

As a result, regulators tend to demand:

• More complete documentation upfront
• Greater clarity in plans and specifications
• Clear lines of accountability between factory and site

Again, this isn’t favoritism—it’s risk management.

Manufactured Housing Adds to the Confusion

Complicating the discussion further is manufactured housing, which is regulated under a federal HUD Code rather than local building codes. Manufactured homes benefit from national preemption, meaning local jurisdictions have limited authority over construction standards.

This often leads to confusion among consumers and even officials, with modular homes mistakenly grouped into the same category. When that happens, modular builders can find themselves explaining not just their project—but the entire regulatory framework.

The Reality: Neither Is “Easier,” Just Different

From an approval standpoint:

• Site-built homes benefit from familiarity and visibility
• Modular homes benefit from controlled production and consistency
• Both face increasing scrutiny as codes grow more complex and departments remain understaffed

Where modular builders run into trouble is not because codes are tougher, but because processes are less standardized across jurisdictions.

What’s Changing—and What Isn’t

Approval authorities are not becoming anti-modular. If anything, many recognize that offsite construction may be essential to meeting future housing demand.

What is changing is expectations:

• More complete submissions
• Better coordination between agencies
• Stronger documentation trails
• Clearer accountability

For builders—modular or onsite—the era of casual approvals is ending.

Final Thought

The real divide in approvals isn’t modular versus site-built. It’s predictable processes versus uncertain ones.

Where regulators understand the construction method, approvals tend to move smoothly. Where they don’t, friction follows—regardless of whether the home was built in a factory or on a muddy lot.

As housing pressures increase, the industry’s challenge isn’t convincing regulators that modular works. It’s helping them see that well-managed processes—onsite or offsite—reduce risk, not increase it.

And that conversation is just getting started.