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Typically these are called "modular homes" in the US. They've been around for quite a while and do make up a certain portion of the new home construction, though not the majority. This approach is not quite as efficient as it initially appears: First, it does nothing for the site construction (grading, excavation, utilities, paving, septic, well, etc.) Those tasks, which make up a decent portion of the project, are done in exactly the same way as in conventional construction. Second, the modular boxes are either A) the width of shipping containers, which severely constrains the house layout, or B) somewhat wider than shipping containers, which makes them oversized loads that require escort vehicles, highway permits...increasing cost. Third, you have to hire a crane to set the boxes, and then make all of the connections between the boxes, and install various mechanical and electrical components, complete the finishes, install staircases, etc. This costs quite a bit and still involves the hiring of various local subcontractors, just like in conventional construction. When you add everything up, modular sometimes saves a little money and often reduces the project timeline (unless there are delays at the factory). But it's not a massive improvement, which is why modular hasn't taken over everything. |