Rahul Bajaj, PE, of PFS TECO, on what plan review actually checks

A buyer orders a modular home and is told the plans are in review. Who is reviewing them, what are they checking, and how is that different from the building permit the local jurisdiction issues?

It depends on the state. In many states with modular programs, the factory-built portion is reviewed either directly by the state or by a state-approved third-party design-review agency. The reviewer is generally checking the building against the adopted building, structural, mechanical, plumbing, electrical, and energy codes, along with any modular-specific state requirements.

The local jurisdiction usually remains responsible for things outside the factory-built scope, such as zoning, foundations, site utilities, site-built construction, installation, and other local permitting requirements.

That distinction is one of the most confusing things for buyers. A state-approved modular building does not usually mean that no local permit is required.

What is the most common reason a set of modular plans comes back for correction, and where does that usually fall relative to the buyer signing a contract?

In my experience, the most common issue is not a major engineering failure. It is incomplete or inconsistent information.

Examples include missing calculations, conflicting information between architectural and engineering sheets, incomplete electrical or plumbing information, missing product documentation, energy-code issues, or design criteria that do not match the project location.

The bigger problem is timing. In some cases, the buyer has already signed a contract and has an expected delivery date before the regulatory package is fully developed. At that point, every correction cycle affects the schedule. The best way to shorten approval is usually not to pressure the reviewer. It is to submit a complete and coordinated package the first time.

A home built in a factory in one state and set in another gets reviewed against which code, and who decides?

The destination jurisdiction controls, not the factory's location.

The important question is not where the factory is located, but where the building will ultimately be installed. The destination state's adopted codes, amendments, and modular-program requirements usually govern the factory-built portion.

That is why a manufacturer cannot simply say a building is "code compliant" without specifying where it is intended to go. A building designed for one state may require revisions before it can be approved in another.

What does the insignia on a finished module certify, and what does it not certify?

The insignia is commonly misunderstood.

It indicates that the module was manufactured under the applicable state modular program, using approved plans and an approved inspection or quality-control process. It is not a blanket guarantee that the entire finished project is perfect.

It does not certify things outside the factory-built scope, such as site foundations, grading, site utilities, installation, or locally constructed work. I tend to describe the insignia as evidence that the factory-built portion went through the required state approval and inspection process, not as a universal warranty of the final building.

How much of the time between contract and delivery is review time, and what makes one project take weeks and another take months?

The first review is often not what creates the largest delay. What usually determines the schedule is the quality of the initial submission and how quickly corrections are resolved.

A complete and coordinated package can move relatively quickly. A project with repeated corrections, missing engineering, changing design criteria, or slow responses from the design team can stretch out significantly.

Modular works best when regulatory review starts early and runs in parallel with manufacturing planning, rather than being treated as the last administrative step before production.

You work with Texas IHB, Washington L&I, Colorado DOH, and California HCD, for example. Where do those programs disagree with each other in ways that cost a buyer time or money? Are they substantially different from each other?

The basic safety objectives are similar, but the administrative systems can be very different.

States differ in who is authorized to review plans, who conducts inspections, how manufacturers become approved, how insignias are issued, what quality-control systems are required, and where state jurisdiction ends and local jurisdiction begins. Some states rely on state staff, some on approved third-party agencies, and others use a combination.

For a manufacturer, those differences create real cost. A company operating nationally cannot necessarily use the same approval process, paperwork, inspection structure, or even design assumptions everywhere. For buyers, most of that complexity is invisible until it affects schedule or price.

Some states have no state-level modular program. What happens to a buyer in one of them, and does that make a project easier or harder?

It can go either way.

Without a statewide modular program, approval may fall primarily to the local authority having jurisdiction. That can eliminate one layer of state administration, but it also removes statewide uniformity.

A manufacturer operating under a mature statewide program may be able to use the same approval framework across dozens of jurisdictions. In a state without that structure, the manufacturer may have to work through the same technical and procedural questions separately with multiple local building departments.

Less state regulation does not necessarily mean less regulatory work.

Where can AI take over the repetitive parts of technical review, and what should it not touch?

AI is particularly good at the repetitive parts of technical review.

It can read large plan sets, identify relevant sheets, extract design criteria, compare information between drawings, find missing information, identify inconsistencies, and flag potential code issues for a reviewer. For example, AI can identify that a structural sheet lists one wind speed while the calculations use another, or that a plumbing plan shows fixtures but does not provide enough information to verify the system.

People get ahead of themselves in assuming AI should independently approve buildings. I see it much more like an extremely fast junior reviewer. It can examine a huge amount of information and surface issues, but a qualified person still needs to make the compliance decision.

When a review is partly automated, who will hold the professional liability for what is missed?

Responsibility sits with the professional or organization issuing the approval, subject to the jurisdiction's rules and the contract between the parties.

Engineers already use structural-analysis software, energy-modeling tools, and other automated systems. Those tools do not assume professional responsibility. AI should be treated similarly. It can assist with the review, but the qualified reviewer remains responsible for the final decision.

That human accountability is especially important in building safety.

How do you see AI reshaping the prefab and modular industry? How does this lead to a better result for the buyer?

I think regulatory efficiency is one of the biggest opportunities.

The whole premise of modular construction is that repeatability and factory production should make construction faster, more consistent, and more efficient. It makes little sense to save weeks in the factory and then lose those same weeks because plans are moving manually between designers, manufacturers, third-party reviewers, state agencies, and local jurisdictions.

AI can make the regulatory side operate more like manufacturing: structured, repeatable, and measurable. I do not think the main opportunity is replacing engineers or inspectors. The opportunity is allowing qualified people to spend less time searching through drawings and more time making engineering judgments.

For the buyer, the result should be fewer correction cycles, fewer surprises after production starts, more predictable approvals, and ultimately a shorter path from contract to completed building.