Percentage completion: The game isn't displaying the percentage of completion on a project that my builders are working on.

The percentage of completion for a building project is not displayed until progress has reached 1%, and the scaffolding appears. The building projects in the game vary greatly in their size, and some projects require significantly more time to reach 1% completion, especially if there are few builders working on it. Be patient and allow the builders to continue working, and the scaffolding will appear, allowing you to monitor construction progress. 

Note: Certain projects never display scaffolding or percentage of completion, since they are more complex projects with multiple phases.