A prefab (prefabricated) house is built in a factory as modules or panels, trucked to the site, and assembled on a foundation in days: a typical two-module home leaves the factory 80-plus percent complete — walls, windows, finishes, even cabinets — and closes up weather-tight the week it arrives. Factory building is no longer fringe: the modular segment of U.S. construction grew through the 2020s as labor shortages squeezed site builders, and per the Modular Building Institute, offsite methods now account for a meaningful and rising share of single-family and multifamily construction — the industry's quiet answer to its own productivity problem.
The pieces arrive on purpose, and the reasons are mostly arithmetic.
What are the actual types?
- Modular: whole room-sized boxes, built to state and local building codes, craned onto the foundation and stitched together — the closest experience to a site-built house.
- Panelized: flat walls and roof trusses shipped for site assembly — more transport-efficient, more site labor.
- Kits and package homes: engineered component sets, from Sears-catalogheirloom tradition to modern SIP (structural insulated panel) packages.
- Manufactured homes: built to the federal HUD code on a permanent chassis — a separate regulatory category, often mislabeled "modular"; the financing and zoning rules differ, so know which you are buying.
Why build in a factory?
Four compounding advantages. Labor: one crew in a climate-controlled plant outproduces site framer teams competing for scarce trades. Weather: materials never soak; schedules run to the calendar, not the forecast — site-built lumber absorbs moisture and dries into the walls, a durability liability factories simply delete. Tolerances: jigs and repeatable assemblies mean straighter, tighter, more airtight envelopes — factory building suits high-performance (passive-house-grade) construction because quality control is repeatable. Speed: foundation proceeds on site while the house builds in the plant; the classic two-parallel-tracks schedule compresses a year to a few months.
What does it cost, really?
The honest answer: prefab is not automatically cheaper. The box itself is price-competitive per square foot with quality site building; the total budget then runs through the same site costs — land, foundation, utilities, permits, transportation of the modules (a real line item that grows with distance and route complexity), crane day, and the on-site finishing (utility connections, porch, driveway, landscaping). Where prefab reliably wins is time-to-finished-house and predictability — fixed factory pricing, fewer change orders, no weather overruns. Where it loses: highly custom designs (factories thrive on repetition), remote sites with hard delivery routes, and markets where site labor is still cheap.
What is it like to live in?
Indistinguishable from site-built, if done right — that is the category's whole pitch. Modern modular homes are real houses: site-built foundations, permanent mortgages (modulars finance like any house; manufactured homes have separate lending tracks), and interiors with the same finishes. The differences a resident might notice are virtues: tight, quiet envelopes; straight lines; and — because factories build to code with third-party inspection at each station — a compliance paper trail that occasionally exceeds site-built practice. The stigma, where it survives, is inheritance from the HUD-code trailer era, and mortgage appraisers have largely followed the financing distinction rather than the jokes.
How do you buy one without surprises?
- Pick the manufacturer by delivered-to projects within 200 miles — transport cost and installer familiarity are local facts.
- Nail the scope split in writing: factory price, transport, crane, set, and the general-contractor scope (foundation, utilities, finish-out) — the classic prefab budget failure is assuming the factory number was the house number.
- Verify code path: modulars are state-code inspected in-factory with third-party approval; your jurisdiction should confirm acceptance before deposit.
- Visit a set day if you can: watching two boxes become a house in an afternoon is the best warranty inspection you will ever attend.
FAQ
Is a prefab home the same as a mobile home?
No. Modular prefab homes are built to the same state and local building codes as site-built houses, finance with standard mortgages, and appraise as real property. Manufactured (mobile) homes are built to the federal HUD code on a chassis — a separate category with different lending and zoning rules.
Are prefab homes cheaper than site-built?
The factory box is price-competitive, but total cost includes land, foundation, transport, crane, and site finishing. Prefab's reliable wins are schedule and price predictability rather than automatic savings; custom designs and remote sites erode the advantage.
How long does a prefab build take?
Typically a few months end-to-end: the modules build in the factory while the foundation is prepared on site, then assembly takes days and finishing a few weeks — versus many months to a year for comparable site construction.
