Where does under construction come from?
Early instances of under construction come in legal contexts, drawing on a specialized use of construction to mean "interpretation" (e.g., under our construction of the terms of the contract). We see the contemporary sense of under construction—buildings in the process of being built—by at least the early 1800s, though construction has been used for "the act of building" since the 1400s. Think of under, in the phrase, as undergoing or underway.
An 1826 Congressional document, as one notable early instance, discusses the erection of certain military fortifications and the workforce required to put them under construction. By the 1930s, perhaps with the boom of skyscrapers, under construction was in common use in a range of official building contexts. Soon after, the phrase metaphorically extended to other, non-structural projects, from government policies to major works of writing in development.
Under construction took on a new meaning with the rise of the internet in the 1990s. Often paired with images of tools and hardhats, web developers would display under construction when a site was being created or redone. By the 2000s, however, internet professionals looked down on under construction, as it appeared both dated and potentially deterred visitors from ever returning.
Who uses under construction?
In formal and informal speech and writing, under construction is widely used for various building projects by professionals and everyday people alike. When used of buildings, under construction usually suggests a new structure being built from the ground up. When used of roads and public transportation, under construction typically communicates repairs and expansions. Signage on work sites around roads or outside stores may display language of under construction to alert or notify the public.
Sometimes, under construction is used as a descriptor (e.g., an under-construction subway tunnel).
In its many metaphorical uses for projects ranging from business strategies to dissertations, under construction can have a positive or negative connotation. On the one hand, under construction means work is happily underway. On the other, under construction means work is incomplete. As noted, use of under construction on a website that is temporarily down is seen as amateurish.
Arizona would be a lot cooler if the entire state wasn’t under construction
@larisa_cookie, April, 2018
Virginia Beach's first Valvoline Instant Oil Change is under construction in Market Square
Eric Hodies, The Virginian-Pilot (headline), April, 2018
Star Wars filming outdoors a short drive from my house this weekend, by the looks of things. The Millenium Falcon is under construction
@pyxl_8, May, 2016