The study of design and implementation factors that leads to the increase of the cost risks during the construction phase is considered as one of the basic rules for the successful task and that will lead to control the cash flow through the construction. There is an attempt in this research to follow up the effective factors on cost risks like the effect of layouts and designs preparing also the effect of contracts types and other factors and its combined impact on real fundamentals
of cash flows and to avoid the differences which may be occurs due to
misunderstanding or any confusion between the contract parties, specially in payments paid by the project owner to the contract. The research includes the field survey which depended on questionnaire that prepared in significant manner and distributed to different parties which have a scientific and practical experiences on projects. The research conclusion pointed out that design requirements is the
major influencing factor that represent (80%) of the project cost overrun risk and then come the other factors having lower values of effect.