A house built in finished sections in a factory to the same state and local building code as a site-built home, trucked to the lot and craned onto a permanent foundation, after which it is inspected by the local building department, appraised against site-built sales, financed with an ordinary mortgage and taxed as real property.
Where the house was assembled is the least important thing about it. What defines a modular home is the code it was built to, because that is what decides how a building department, an appraiser, a lender and a county assessor each treat it. Built to the local building code, it is a house in every one of those eyes.
The word people confuse it with is manufactured, and the confusion is expensive rather than academic: the two are built to different codes, financed under different rules and valued by different methods.
The code is the definition
A modular home is engineered and built to the building code the destination jurisdiction has adopted, which is normally a version of the International Residential Code. Change the county and the plans change with it, because the snow load, the wind load and the seismic design are local. A state-approved third party inspects the modules inside the plant, since the local inspector cannot look behind a wall that was closed in another state, and the local building department inspects everything on site: the foundation, the connections between sections, the utility tie-ins and the final occupancy.
A manufactured home is built instead to the federal HUD code, one national standard, and stays on the steel chassis it was built on. That single difference is why a manufactured home may be titled as personal property, may sit on leased land and pay lot rent, and may need a specialized loan, while a modular home does none of those things.
How one gets built and set
The factory builds two or more modules complete with framing, wiring, plumbing, insulation, drywall, cabinets and finishes, indoors, on a line, unaffected by weather. Build time commonly runs six to twelve weeks once a slot opens. Meanwhile a contractor prepares the site: engineering, permits, utilities and a permanent foundation poured and surveyed to the factory's dimensions.
Delivery day is one day. The sections arrive on carriers, a crane sets them on the foundation, and they are bolted and strapped together and made weathertight. What follows is commonly four to eight weeks of joining seams, ridge and roofing, siding, driveway and final inspections, ending in a certificate of occupancy. From then on it is a house and nothing about owning it is different.
How to tell what a particular home is
The labels are the proof, and they are worth finding before making any assumption about a home you are buying. A manufactured home carries a red HUD certification label on the exterior of each section and a data plate inside. A modular home carries the label of the state or third-party agency that inspected it in the plant, commonly in a cabinet, a closet or the electrical panel area. In Nevada, factory-built housing is regulated by the Housing Division under NRS 461 and carries a state insignia, and the current requirements are worth verifying with the division rather than assumed from a home's age.
The paper record is the other tell. A modular home appears on the county assessor's roll as real property with a normal year built. A manufactured home may appear with a title, a vehicle-style identification number, or a conversion to real property recorded against the parcel. Where the two records disagree, believe the recorded documents.
What it is not
Prefab is the umbrella word, not a type: it covers modular, manufactured, panelized and kit homes together, so a listing calling a home prefab has told you nothing yet. Panelized homes ship flat walls that are stood up and finished on site, which is site-built construction with a head start rather than modular. A mobile home is a manufactured home built before June 1976, when the HUD code took effect, and the distinction matters because most lenders will not finance one.
Modular is also not a quality level. The construction is code-compliant by definition and inspected twice, and the factory setting gives tighter tolerances and dry materials. What varies is the finish level ordered, exactly as with any builder.
Questions people ask
Do modular homes appraise like regular houses?
Yes. An appraiser values a modular home against site-built comparable sales because that is what it legally is, and lenders apply no manufactured housing overlay to it.
Can you get a conventional mortgage on a modular home?
Yes, and FHA, VA and USDA lending applies too, on the same terms as a site-built house once the home is set on its permanent foundation. During construction the usual instrument is a construction-to-permanent loan that converts at completion.
Are modular homes cheaper than site-built homes?
The structure commonly costs less per square foot and goes up faster, but the land, foundation, utilities and crane are the buyer's, and in the Las Vegas valley those can be most of the total. Compare finished cost on the same lot rather than factory prices.