Modular-built homes are produced in a factory as three-dimensional modules that may be combined on-site to make level entry or
basement homes. The houses are typically set on full-perimeter foundations—a crawl space or full basement—but may also be placed on surface-mount foundations. Insulation, air/vapour barrier, plumbing, wiring, exterior siding and other construction details are largely completed in the factory. Interior work is usually well-advanced, including drywall, trim, flooring, cabinets and bathroom fixtures.