The general rule of thumb for construction is that if you want it, you have to buy it. Changes to work rules, locations, schedule and scope incurred due to the Coronavirus were not purchased as part of the buy-out in existing projects, and many of these items will have cost impacts to project owners.
Shutting down and starting up projects takes CM labor. Maintaining a jobsite during an extended shutdown has other costs as well.
Adding a second shift to permit social distancing may or may not have impact on trade costs, depending on the trade and related union or other contracts. However, managing that second shift was not considered in the CM or GC general conditions costs, and a change request here is likely.
Jobsite inefficiency due to social distancing – very careful scheduling and probable review and changes to scheduling assumptions will be required if social distancing is to be maintained. No schedules had assumed those issues if bid prior to the rules being implemented.
Schedule adjustments – Expect schedule related changes to be a significant issue, as site access becomes more difficult, achieving pre-virus schedules will be increasingly difficult. These changes will be both for cost and time.
Of course, professional CM's will work hard to limit their client's exposure to these costs, but it is prudent to assume that they will not be able to contain all risks.