What are the principal advantages of using a single building information model of the existing conditions as the foundation for modeling proposed additions or renovations?

• Why not create a separate model for the new proposed design?

It is a good idea to begin modeling any additions or renovations using the model of the existing foundation as the starting point because the project already has a datum, established elevations, and family libraries that will ensure that any proposed construction remains consistent and viable with the structure that already exists. If you were to create a separate model for the new proposed design, it would likely get complicated and there could be a high risk of conflict between some aspects of the proposed design and the existing structures.

What sort of complexities are introduced when you construct a building complex in phases?

• What happens at the interfaces between the buildings as the phases advance?
• How can you plan and prepare for these complexities as your create your initial building model?

What are the principal advantages of using a single building information model of the existing conditions as the foundation for modeling several proposed design alternatives for a portion of the building?

• Why not create a separate model for each of the design alternatives?

The main advantage of using a single BIM as the foundation for several design alternatives is that there are core components that don't change between the different alternatives and if you are working in a single model, any changes you make to these core components will automatically be reflected in all of your design alternatives. If you were to create a separate model for each design alternative you would then need to go and make the same individual adjustments to each of the models. So for example, if you were deciding between two staircase alternatives but at some point you decided to try a new color for the walls of the building, it would be easy to update the color of the walls in all of the staircase alternative scenarios if you are working from a single BIM, but if you have a separate model for each staircase alternative, you would need to change the wall color in each model separately.

In your project, which features of the proposed design did you choose to model as design alternatives?

• Why did you choose these building features? And what were the biggest challenges in modeling them as the design alternatives?