If both are built in a factory, what makes a modular home different from a manufactured home?

Published September 28, 2026

Summary

The difference is the rulebook, not the factory. A manufactured home is built to HUD's federal construction standards, and the federal definition says it sits on a permanent chassis. A modular home is also built in a factory, but it has to meet the building code where it is placed and needs a local building permit. "Prefab" is a loose word for anything factory-built, and federal rules don't treat it as a category.

The short version

	Manufactured home	Modular home
Built to	HUD's Manufactured Home Construction and Safety Standards	State and local building codes at the site
Local building permit	Not required, per the Census Bureau	Required, and subject to local zoning
Chassis	Built on a permanent chassis (current definition)	Not covered by the federal standards
Census price survey (MHS)	Covered	Not covered

The federal definition also has a size test: a structure that is at least 8 feet wide or 40 feet long when it is being moved, or at least 320 square feet once it is set up. HUD's standards can preempt state and local laws that don't conform to them.

Two plates tell you which one you're looking at

Every transportable section of a manufactured home carries a HUD certification label, a small aluminum plate about 2 by 4 inches. The regulation puts it at the taillight end, roughly a foot up from the floor and a foot in from the road side. On it, the manufacturer certifies that the home was inspected under HUD's requirements and built to the federal standards in force when it was made.

Inside, usually near the main electrical panel, there is a separate data plate. It lists the plant that built the home, the serial number, the date of manufacture, the label numbers, and the wind and roof load zones it was designed for. A listing that says "mobile home" tells you little. The two plates tell you what was built and to which standard.

Why the price figures don't line up

The Census Bureau's Manufactured Housing Survey reports average prices of new HUD-code homes. Dealers are told to include their set-up costs, and Census adds that some costs to make a home ready to live in may still be missing. Modular homes aren't in that survey at all.

Site-built numbers have their own quirks. A contractor's price for building on your lot leaves out the land, while the sale price of a new spec house includes it. Our build-or-buy guide puts those two figures side by side. Line up any factory-built quote against the same scope before deciding which one is cheaper.

The 2026 proposal on multistory homes

On June 12, 2026, HUD published a proposed rule (Docket No. FR-6537-P-01) that would let a multistory manufactured home meet the chassis requirement with only its lowest sections on a permanent chassis. HUD estimated that requiring a chassis under upper-floor sections adds $4,800 to $6,700 per home to production, transport and installation. Before HUD's advisory committee met on the idea, modular builders and a modular trade association sent it comment letters.

Comments closed on August 11, 2026. The rule has not been finalized, and the definition in the Code of Federal Regulations still reads "built on a permanent chassis."