This chapter explains the pre-construction design and cost-planning stages. Cost planning is a demanding, interactive process that must involve all members of the design team and the client so that decisions can be evaluated and integrated properly. The Technical Design Stage is the crucial stage in controlling the cost of the detailed or documented design. Everyone in the design team should redouble their efforts in the Technical Design stage to prevent this unsatisfactory conclusion. Cost monitoring is carried out from the developing Technical Design information. The cost planner must effectively monitor costs by providing cost checks during the Technical Design stage, which is mainly concentrated on the detailed technical design development and production of tender documents. There are three characteristics of an element that make it important to design the element early in the Technical Design stage: unreliable cost target; large cost target; and a design that affects the design of other elements.