In a way, all construction is modular. Raw materials are processed into dimensional lumber, concrete masonry units, and steel anchor bolts (to name a few) before they arrive at the construction site. Doors and windows get fully assembled in factories, as do structural components like roof trusses. The line dividing “regular” from “modular” is quite fuzzy.

In this spirit, a column in Modern Steel Construction magazine challenges the conventional knowledge that modular construction is a single strategy. “Modular” in fact encompasses a wide range of possibilities. The author lists three categories in order of how much assembly is done off-site:

1. The “kit-of-parts” method. The building’s structural design minimizes the number of different pieces for construction, so many beams and columns are the same size and therefore interchangeable, like K’nex or an Erector set. This approach reduces fabrication and installation time and minimizes error.
2. The panelization method. Panels (such as individual walls and sections of floor) are fabricated offsite and hoisted into place. Cornell University’s West Campus Residential Initiative dormitories were built using precast concrete panels, so they fall into this category.
3. The volumetric method. Entire rooms are fabricated offsite and hoisted into place. The Stack in New York and B2 in Brooklyn (both discussed previously on this blog) are examples of the volumetric method in use.

Cornell’s West Campus Residential Initiative dorms, with precast concrete walls and floors, illustrate the panelization method of modular construction.

All three methods share advantages over the kind of construction where most parts are assembled and placed onsite. A factory setting increases productivity (no weather delays or poor workmanship), improves worker safety (no falls), and reduces waste (no over-ordered concrete for example). These benefits allow modular construction methods to shorten the average commercial construction schedule by more than a third, 39% according to the article.

Residential construction can benefit from the same three techniques. In fact, two of the main downsides of modular strategies – modules may be unwieldy to transport, and developers may be unable to afford high up-front costs for prefabrication – are greatly diminished with the smaller size of a single-family house. At the smallest scale, you might say that every tiny house on wheels is a one-module application of the volumetric method.