The development of the slotted steel stud made it possible to use steel in external walls in countries with cold climate, like Sweden. By slotting the web the thermal bridges are significantly reduced. Several fabricators of lightweight constructions in Scandinavia now have slotted studs in their range, intended for load-bearing external walls in single family houses and for infill walls in blocks of flats. The development of the slotted stud has also led to the development of the building system for residential called Light Steel Framing.This paper mainly considers design methods for slotted steel studs for external walls. The importance of the slotted stud for the Light Steel Framing System is lighten up by a description of building components as exterior walls, interior walls and light weight floor structures. The thermal properties, sound insulation, springiness and vibrations, fire proof are described as well as building services, architecture, planning and production.