Your teams are too big: break them up.
Newspapers sometimes run contests to see who can produce the best summary of a epic book in one hundred words or less. Here is my 100-word version of “The maximum team size for effective working” drawing from an excellent article by Christopher Allen entitled The Dunbar Number as a Limit to Group Sizes.
Teams should be between 5 and 9 people. Below this they lack resources (2), are unstable (3) or spilt into factions (4). Above this team members don’t get enough individual attention due to lack of time available for grooming to maintain relationships. This is made even more difficult if they are virtual teams. Teams start to work again when they reach around 25 as it becomes possible to spilt them up into distinct sub-teams of 5 to 9. (78 words)
This also broadly agrees with a finding in one of my favourite books – The Mythical Man Month by Fred Brooks who was a pioneer in discovering the unexpected burden it places on team communications when new members are added to teams. This work resulted in the famous maxim often referred to as Brooks Law that “adding resource to a late software project only makes it later.”
This idea of splitting teams into sub-teams is discussed in my article on Team communication patterns: key lessons from nature, where I review the patterns of communications in teams and suggest where they may indicate that we have failed to recognise a hidden sub-group which needs to be made explicit in the team structure.
This raises the BIG QUESTION of how we can be more effective in “virtual grooming”, i.e. taking care of relationships in teams that do not meet much or even at all, but that is another discussion!