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Project Phases and Phased Design

BIM for Architecture, Engineering, and Construction Curriculum

Overview

Many projects, whether new construction or renovations, are designed and constructed in distinct phases. These phases can represent either the time periods themselves or the state of the project at specific points in time. 

In this lesson, students explore two applications of project phases and phased design and will learn how to:

  • Use project phases to organize the information in a building model based on the project phases during which different portions will be constructed.
  • Use project phases to coordinate the elements in a renovation project and display accurate views of the as-built conditions, demolition work, and proposed new design.

By defining project phases and using phase-based filters to determine the information presented in model views, the building model can be used to facilitate design and visualization at each of the stages in the project lifecycle.

Modeling Phased Projects in Autodesk Revit

Phases are distinct, separate time periods or “milestones” within a project. Every project includes at least one phase, and by default, Autodesk® Revit® software defines two phases (named Existing and New Construction) in new projects. The project team can rename these phases or add as many phases as needed to accurately describe the project.

All elements in the building model have two properties that control the time periods during which the element is considered to be present—Phase Created and Phase Demolished. In project phases before the Phase Created or after the Phase Demolished, the element is ignored and will not be displayed in model views.

The visibility of model elements in any view is determined by a combination of the Phase property for that view and a Phase Filter that determines how elements will be displayed based on their creation and demolition state relative to the current phase. Every element is assigned a status relative to the phase of the current view:

  • New—If the element was created in the phase of the current view
  • Existing—If the element was created in an earlier phase and continues to exist in the current phase
  • Demolished—If the element was created in an earlier phase and demolished in the current phase
  • Temporary—If the element was created and demolished during the current phase

Phase filters control the appearance of elements based this phase-based status by specifying how elements of each status should be displayed:

  • By Category―The display settings in Visibility and graphics for that view will be used to display any objects in that Phase Status.
  • Not Displayed―Any object that is that Phase Status will not display in the view.
  • Overridden―Any object that is that Phase Status will use the Graphic override that is set on the Graphic Overrides tab of the Phases dialog box.

This phase information and phase filters are commonly used to create phase-specific views of the building model that present or hide the model elements in a way that is most appropriate for that project phase. The following table illustrates one scheme for using phases and phase filters to create views for specific project uses.

Phased New Construction

Many projects consisting of several buildings are designed and constructed using a phased process that divides the work into manageable packages based on the planned construction sequence. For these projects, it is often useful to assign the building model elements to distinct phases so views can be filtered to show the elements relevant to a specific phase.

By setting the phase property and phase filters for each model view and schedule, we can control the appearance of building model information and create phase-specific project documentation. This approach simplifies the management of complex building models and assists in the preparation of construction documents by allowing designers to focus on a single phase at a time.


Phased Renovations

Another common design situation in which project phasing can be useful is renovations or retrofits of existing structures. Renovations are typically modeled using two phases:

  • Existing—which is used to model the existing as-built conditions
  • New Construction—which is used to model the proposed design


Demolition is typically not modeled as a separate phase. Rather, it is better practice to indicate the building elements to be demolished by setting the Phase Demolished property for these elements to the New Construction phase. Demolition plans can then be created by using a phase filter to display and highlight the elements to be demolished.

An important consideration to keep in mind while modeling renovation projects is that building elements can only be created or demolished between phases. When only a portion of a building element should be demolished, it is often helpful to split that element into individual parts, so that each segment can be treated separately. 

Building elements created in prior phases should not be edited, stretched, reshaped, or deleted because these operations will change their appearance in all phases. This limitation mirrors the physical reality of how objects can change between phases—you can typically create new objects and demolish existing ones, but physical elements typically cannot be stretched to a new configuration.