Parsons School of Design
The tiny house movement was an architectural and social movement that promotes houses with small square spaces, with intentions to save financial costs and the environment.
Tiny House Movement
While there is no official definition of a tiny house, it is generally thought of as a small house, typically sized under 600 square feet. While they can be built on foundations, most tiny homes are built on trailers. This style of tiny house is often referred to as a THOW (tiny house on wheels).
There are several advantages to building a tiny house on a trailer. The two most favorable being, mobility and getting around local rules that dictate minimum structure size. Since a house built on a trailer is not on a permanent foundation, it normally is not governed by local building codes. Many municipalities dictate a minimum home size (square footage), which makes building a tiny house on a foundation not legally possible.
Source: Tiny House Builders, https://www.tinyhomebuilders.com/help/tiny-house-movement