Cold-formed steel is made from quality steel plate or coil that is formed into shape either through press-braking (for heavy gauge metal plate) or bend braking (for light gauge metal sheet) (see Figure 1),or more commonly, by roll-forming through a series of dies at ambient temperature (see Photo 7).No heat is required to form the section and thus the name "cold-formed steel" is acquired.The use of cold-formed steel as primary structural members in building design and construction has been prevailing in countries such as Australia, Mainland China, Japan, European countries and Northern American countries, etc.In the Code of Practice for the Structural Use of Steel 2005 (i.e.Steel Code 2005), it gave recommendations only for the design of cold-formed sheet profiles (i.e.thin gauge corrugated open sections) with nominal thickness up to 4mm and other cold-formed steel sections (both open sections and closed hollow sections) with nominal thickness up to 8mm.Welding was not permitted and this hampers the wide application of cold-formed steel in building design and construction.In the advent of the Code of Practice for the Structural Use of Steel 2011 (i.e.Steel Code 2011), design guidelines are substantially formulated for the use of cold-formed steel hollow sections with nominal thickness up to 22mm and cold-formed steel sheet pile sections with nominal thickness up to 16mm.Their requirements on tensile strength, notch toughness and ductility should comply with the essential requirements for the parent hot-rolled steel.Another revamp in the Steel Code 2011 is the permission of welding within a length of 5 times the section thickness on either side of cold-formed zone.Occasionally, sections may be cold-formed with tight corners which violate the minimum radius-thickness ratio and no pre-normalizing treatment is done.In these circumstances, the Registered Structural Engineer should submit a valid Welding Procedure Specification for the approval of the Building Authority before the carrying out of welding works in cold-formed zones.During cold-forming of steel sections, high residual stresses are created at the bent locations.This may render cracking/peeling at bent corners when the sections undergo hot-dip galvanizing bath.Special consideration should be made for this particular phenomenon at the time of order placement.As the Steel Code 2011 promulgates the use of cold-formed steel, it offers the construction industry an alternative to choose.Now that special steel grades to BS 10149 Part 2 and Part 3 are stipulated in the Steel Code 2011, very tight comers of cold-formed sections with inside bend radius equal to the plate thickness are permitted.It is anticipated that peculiar section shapes generally not available from hot-rolled products can be tailor-made using the cold-forming technologies so as to produce an aesthetic outlook that tallies with innovative design conceived by the architects.