The industrialisation of the building industry has been going on for some time now, but with small steps, so it is elements of the building the have been industrialised, elements like windows, precast concrete panel and wood houses in self-assembly kits. But to reorganize the entire building process into a production has not yet been a success. Fonden for billige boliger (The foundation for inexpensive housing) was established when Copenhagen commune made a plan, the 5x5 plan. This plan should insure that 5000 homes would be build in 5 years, and that they would only cost 5000 kr./month (2005-prices). Because of the global financial situation the project is on standby, and the 5 years can't be kept. However Fonden for billige boliger is still convinced that it is possible to create the 5000 homes within a reasonable time. The first inexpensive homes have already been build. They are made from modular room sections, which where made in Estonia. This factory also made the next inexpensive home project, that's almost finished, and ready for moving in. By evaluating the eight parameters: Location, aesthetics, user-friendliness, technical features, environmental considerations, health and security, time and economics, it is shown that there are many circumstances to consider and this report looks into if the industrialised building process can be more efficient. By using lean and adapting the theory to the building industry it is possible to make the industrialised building process more efficient. Furthermore by the use of lean, there is in this report made a new value chain that will industrialise the building process, all the way from when the construction programme is made. In the future, the architect will have the opportunity to design buildings made of modular room sections, before the manufacturer is known. This will be possible as a standard has been made, that gives directions on what specifications the modular room section has.