Even though a “horizontal structure” is flat in nature, it does still need a (vertical) support structure.

The main purpose of a support structure is to help managers build lasting relationships and achievements with teams. There are two basic type of support structures that managers can mix and match when building or working with teams, depending on the requirements as each has its own attributes.

• Informal structures don’t define rigid roles and responsibilities, they are open to interpretation and people can define their own roles and swap roles as needed, hence they are less resource intensive, more flexible and less binding on members; Informal structures help promote open discussion and communication among its team members; and
• Formal structures are more rigid and roles/titles might be defined where members have specific responsibilities; this makes them more resource intensive but less ambiguous; they require some logistical skill and expertise to implement. These structures are great when consistency and quality are important factors.

It’s important for management to recognize what type of structure needs to be in place and when its put in place; as “when” a structure is erected, it can play an important role in the success of the teamwork initiative. If too much formality is introduced early, people might feel there is no difference in the “horizontal structure” and the “vertical structure” where vertical structures are rigid, formal and bureaucratic and would be less motivated to work with the initiative. In contrast, waiting too long to build a support structure or the lack of a support structure can hinder the ability of the team to successfully work together as a team, especially when they need to be able to adapt when in tight spots.

Since the resources and effort required are greater when setting up formal structures, informal structures are great for short projects, however when the projects will go on for a long period of time or are of large scale, formal structures would be more suited as they are less ambiguous and will stay well formed longer (as they are more solid than informal structures).

Authority and roles in informal structures are more ambiguous and can be swapped around; In formal structures, the roles and responsibilities are more definitive, hence less ambiguous and in that regard, formal structures would work best in situations where important decisions need to be made.

[Source: Moving from the Heroic to the everyday: Hopkins, Couture, Moore]