Kit homes, also known as Building Systems, consist of modular, panelized or log building components produced in a quality controlled environment.

Because modular and panelized homes can be constructed in a factory while the site is being prepared, construction can often be completed within four to eight weeks.

Kit home manufacturers use computers to create customized plans to meet the design and budget needs for both affordable and high-end luxury home buyers. Choosing one of the manufacturer's existing models is the least expensive way to build, although most will offer to make modifications to their packages or design custom homes at additional costs.

Like conventional site-built construction, all building systems must comply with codes in the region in which they are delivered-unlike manufactured ("mobile home") HUD-Code housing, which is built to a separate, federally administered and enforced code.

Modular buildings, which consist of two or more sections combined to create the finished building, are 90-95% complete when shipped from the factory to the building site to be affixed to a conventional foundation.
Panelized buildings are constructed of exterior wall panels made of traditional lumber, prefabricated metal stud walls or structural insulated panels (SIPs) to form the "skeleton" of the building. Panels tend to provide more opportunity of customization than modular homes.

SIPs also offer substantial energy advantages compared to traditional wood- framed, fiberglass insulated walls.

Log homes can be constructed of manufactured flat or round logs, or hand-crafted logs. Some log home manufacturers also offer packages of just walls and windows or log accents for use on conventionally framed homes.
Some manufacturers sell just the shell, which includes a complete set of wall panels, floor decks, roof and floor trusses, roof sheathing, and exterior doors and windows (sometimes pre-hung). Others offer "full packages," or everything that's required to just move into the home, even appliances.