As more emphasis is on risk analysis, it is an important phase in the Spiral model, which requires expert associates to execute. Apparently, it increases the overall cost, and so, it is not a good fit for smaller projects.

In the worst cases, Spiral may go on infinitely, which creates wastage on its investment in terms of effort and cost.

As Spiral has a high degree of complexity, and is relatively difficult to follow strictly, documentation is more due to the execution of multiple intermediate phases of the development cycle.