Why Phasing and Design Options Matter
On renovation projects, campus expansions, and multi-phase developments, one of the most common mistakes is creating separate Revit models for each phase or design alternative. This approach multiplies file management effort, creates coordination errors when changes must be propagated across multiple files, and loses the ability to compare phases or alternatives side-by-side in a single view.
Revit solves these problems with two distinct but complementary tools: Phasing for managing the timeline of construction (existing, demolished, and new elements coexisting in a single model) and Design Options for managing design alternatives that must be evaluated and presented before a decision is made.
Understanding which tool to use — and when to use phasing versus design options versus separate models — is a key BIM management skill that separates efficient project teams from those who waste hours maintaining duplicate data.
Phasing Concepts
Phasing in Revit is built on a timeline model. Every element in the Revit model has two phase parameters:
- Phase Created: the phase during which this element was constructed or introduced
- Phase Demolished: the phase during which this element was removed (if applicable; otherwise set to None)
These two parameters, combined with a view's Phase and Phase Filter settings, determine what each view shows. A view set to Phase = "New Construction" with Phase Filter = "Show New Only" displays only elements created in the New Construction phase. The same view set to "Show All" would display existing, demolished, and new elements simultaneously with graphic overrides distinguishing their status.
The power of phasing is that all this information lives in a single Revit model. No separate files, no manual coordination between models, no risk of forgetting to update the demo plan when the new construction plan changes.
Default Phases and Adding Custom Phases
Every Revit project starts with two default phases: Existing and New Construction. These are sufficient for simple renovation projects. Access phase management through Manage > Phases.
For multi-phase projects, add custom phases by clicking the Insert button in the Phases dialog. Common phase sequences:
- Existing → Phase 1 Demolition → Phase 1 New Construction → Phase 2 Demolition → Phase 2 New Construction
- Existing → Building A (complete) → Building B → Building C → Future Expansion
- Existing → Demo → Base Building → Tenant Improvement → Occupancy
Phases are sequential — Revit understands that elements demolished in Phase 1 no longer exist in Phase 2. You cannot demolish an element in a phase that precedes the phase in which it was created.
The Phase Sequence order matters. Revit reads phases chronologically from top to bottom in the Phases dialog. Drag phases to reorder them. A common mistake is creating phases in the wrong order, which causes incorrect graphic display in phase-filtered views.
Phase Filters: Controlling What Each View Shows
Phase Filters are the view-level setting that determines how elements of different phase states appear. Go to Manage > Phases > Phase Filters tab. Revit ships with several default filters:
| Phase Filter | What It Shows | Typical Use |
|---|---|---|
| Show All | All elements at all phase states with full overrides | Coordination, overview drawings |
| Show Complete | Existing elements that survive; new elements built | Simulating completed condition at any phase |
| Show New Only | Only elements created in the view's phase | New construction plans only |
| Show Previous + Demo | Elements from prior phases + elements being demolished | Demolition plans |
| Show Previous + New | Existing elements surviving + new elements | Before-and-after comparison |
Each filter has four columns defining how each phase state is displayed: New, Existing, Demolished, and Temporary. Each state can be set to: By Category (normal display), Overridden (custom graphic override), or Not Displayed. Create custom Phase Filters for project-specific needs — for example, a "Show Demo Only" filter that hides new work and existing work to produce a standalone demo plan.
Graphic Overrides for Phase States
In the Manage > Phases > Graphic Overrides tab, define how each phase state looks on drawings. Standard conventions:
- Existing elements: shown in halftone (50% gray) or a lighter lineweight to indicate pre-existing conditions
- Demolished elements: shown dashed, in a specific color (often red or gray), with an overridden linetype
- New Construction: shown at full weight, solid lines, normal category colors
- Temporary: used for shoring, formwork, and temporary construction elements — typically shown dashed in a distinct color
These overrides apply globally across the project. Fine-tuning a specific view's appearance is done through View-specific Visibility/Graphics overrides layered on top of the Phase Filter overrides.
The Demolition Workflow
The standard renovation workflow in Revit follows these steps:
- Set all existing elements to Phase Created = Existing: either model them in an Existing phase view, or select all elements and batch-set their Phase Created parameter. If you are importing a scan or CAD base, model the existing conditions in a view set to Phase = Existing.
- Switch to a demolition plan view: create a floor plan view with Phase = New Construction and Phase Filter = Show Previous + Demo. This shows existing elements in their halftone state ready for annotation.
- Mark elements for demolition: select a wall, column, or other element that will be removed. In instance properties, set Phase Demolished to the phase when it will be demolished (e.g., "Phase 1"). The element immediately renders with the demolished graphic override in the demolition view.
- Model new construction: in a new construction view (Phase = New Construction, Phase Filter = Show New Only or Show Previous + New), place new walls, columns, MEP systems, and other elements. These automatically have Phase Created = New Construction.
- Create phase-filtered views for each deliverable: demo plans, new construction plans, and existing condition plans are all the same model data — just different view settings.
A critical rule: never delete existing elements to remove them. Always set Phase Demolished. Deletion permanently removes the information; Phase Demolished preserves it for the demolition plan and historical record.
Design Options: Managing Alternatives
Where Phasing manages construction timeline, Design Options manage design alternatives that exist at the same point in time. Use Design Options when a client has not yet decided between two or more design approaches — unit layouts, facade materials, lobby configurations, structural system types.
Access Design Options at Manage > Design Options. The Design Options dialog manages:
- Option Sets: a group of related alternatives. Example: "Unit Mix" option set with options "Studio Layout", "1BR Layout", and "2BR Layout"
- Options: individual alternatives within a set. One option is the Primary option (shown by default in views that display the main design); others are Secondary
To add elements to a specific option: activate the option (click it in the Design Options dialog so it shows as active), then model your elements normally. Those elements are automatically assigned to the active option and appear only when that option is displayed. Elements not assigned to any option set — walls, columns, the structural grid — are shared across all options (they appear in all options automatically).
Creating Option Sets with Variants
A typical design options workflow for a residential tower floor plate:
- Go to Manage > Design Options. Click New Set. Name it "Unit Layout".
- Click New Option. Name it "Studio Mix". Set as Primary.
- Click New Option. Name it "1BR Mix". Click New Option. Name it "2BR Mix".
- In the main model, place the shared elements (exterior walls, core, columns) — these are not in any option.
- Activate "Studio Mix". Model the interior partition walls and bathroom/kitchen units for studio configuration.
- Activate "1BR Mix". Model the 1-bedroom partition layout in the same floor area.
- Create three floor plan views. In each view's Properties, set Design Option to the corresponding option. The Studio view shows the studio layout; the 1BR view shows the 1BR layout.
- Place each view on its own sheet and present the three alternatives to the client.
Changes to shared elements (the core, exterior walls) update across all options simultaneously. Changes to option-specific elements affect only that option — the definition of a true BIM design alternative workflow.
Accepting a Primary Option
When the client selects a design option, use Manage > Design Options > Accept Primary to merge the primary option into the main model and delete all other options in that set. This is a one-way, irreversible operation — always save a backup model before accepting. After accepting, the chosen design elements become permanent model elements with no option assignment; the other options and their elements are permanently deleted.
Best practice: do not Accept Primary until the decision is contractually confirmed and all consultants have been notified. Secondary options are invisible to linked model users (MEP engineers, structural engineers), which can cause coordination problems if an option is accepted late in the process without informing the team.
Phasing vs. Design Options vs. Separate Models: Choosing Wisely
| Scenario | Recommended Tool | Reason |
|---|---|---|
| Existing building renovation with demo and new work | Phasing | Single model, demo plan auto-generated, phase sequence enforced |
| Multi-phase campus expansion over 10 years | Phasing | All phases in one model, year-by-year views generated from same data |
| Client choosing between 2 facade options | Design Options | Both options visible, side-by-side comparison, accept when decided |
| Evaluating structural system: concrete vs. steel | Design Options | Structural engineer models both, team reviews, one accepted at SD |
| Two completely separate buildings on same campus | Separate models + linked | Different building forms with separate permit packages benefit from separate files |
| New building vs. major addition (different architects) | Separate models + linked | Different teams, different scopes, link for coordination |
Best Practices
- Name phases and options clearly: "Phase 1 - Podium", "Phase 2 - Tower A", "Option A - Brick Facade" are clear. "Phase 1" and "Option 1" are not.
- Finalize design options before CD phase: carrying multiple active design options into construction documents creates coordination risk and confuses consultants. Accept or eliminate options at the end of Design Development.
- Use Design Options only for client decisions: do not use Design Options as a version history tool or a way to save old designs "just in case". That is what file backups are for.
- Document the phase strategy in the BEP: the BIM Execution Plan should describe the phasing structure, the demolition workflow, and how phase-filtered views are named and organized. New team members need this roadmap to avoid accidentally placing new elements in the wrong phase.
- Test phase-filtered views early: set up at least one demo plan and one new construction plan view at project start and verify the phase filters and overrides work correctly before the model is populated with hundreds of elements.