Maximum Buildable Area
with Revit Design Options
Study zoning envelopes & generate design alternatives — all in one model
Learn how to use Revit's Design Options tool to model the maximum allowable building envelope under zoning constraints, then branch into multiple design alternatives — BCR limits, height caps, setback rules — without ever duplicating your project file.
Most architects reach for Design Options only when a client wants "two versions of the lobby." But the tool is far more powerful than that. Used early in the process, it becomes a zoning envelope engine — letting you model the maximum buildable mass under BCR, FAR, height, and setback rules as one option, then layer design proposals on top as alternatives, all within a single Revit file.
This post covers the complete workflow: setting up the option structure, building the regulatory envelope, creating alternatives, managing visibility, and presenting the comparison to a client or review board.
01 What are Design Options
Revit's Design Options (Manage tab → Design Options panel) lets you store multiple versions of a portion of your building within a single project file. Each Option Set represents a decision point; each Option within that set is one possible resolution of that decision.
Every element in Revit belongs to either the Main Model (always visible, shared across all options) or a specific Option (visible only when that option is active or shown). The main model is the right place for the site, terrain, shared levels, and the regulatory envelope mass. Design options are the right place for competing design proposals.
Why this works for zoning analysis
Zoning analysis requires you to understand the maximum permitted envelope first, then propose designs that fit within it. Design Options maps perfectly onto this sequence:
envelope
(main model)
Max density
proposal
Mid-rise
proposal
Low-rise
proposal
primary &
archive
One file. One set of shared levels, grids, and site data. No copy-pasting between duplicated project files. When the site boundary changes, you fix it once in the main model and every option instantly reflects the update.
02 Setting up the Design Option structure
Step-by-step: create the option set
- Open Manage tab → Design Options panel → click Design Options button to open the dialog.
- Click New under Option Set. Name it something descriptive: Building Mass Strategy
- Revit auto-creates Option 1 (primary). Rename it to Mass A — Max Envelope (your zoning-limit study mass).
- Click New under Option to add more alternatives. Name them: Mass B — Tower Podium, Mass C — Courtyard Low-rise, etc.
- Close the dialog. The current primary option is now active for editing.
Prefix option names with a letter (A, B, C…) and a short descriptor. Revit sorts options alphabetically in the dropdown — good names make view templates and schedules self-documenting later.
Recommended option set structure for zoning studies
| Option Set | Options inside | Purpose |
|---|---|---|
| Building Mass Strategy | A — Max envelope B — Tower podium C — Courtyard block |
Primary massing comparison |
| Parking Configuration | P1 — Underground P2 — Podium |
Structural/programme impact |
| Roof Form | R1 — Flat R2 — Sloped |
Height limit sensitivity |
Keep option sets focused on one decision at a time. A single option set with ten options is hard to manage. Three sets with three options each gives you 27 combinable outcomes while staying legible.
03 Modeling the maximum buildable envelope
The maximum buildable envelope lives in the Main Model, not inside any option. This way it is always visible as a reference silhouette regardless of which design option is active — a constant reminder of what the regulations allow.
Inputs you need before opening Revit
| Regulatory parameter | Example value | Source |
|---|---|---|
| Zoning district | Type-2 General Residential | Eum portal / zoning map |
| BCR (Building Coverage Ratio) | 60% | Seoul City Ordinance Art. 54 |
| FAR (Floor Area Ratio) | 200% | Seoul City Ordinance Art. 55 |
| Absolute height limit | 18 m | Building Act Art. 60 |
| North daylight setback | ≥ 1.5 m; H/2 above 9 m | Building Act Art. 61 / Decree Art. 86 |
| Road setback (building line) | Per road width class | Building Act Art. 46 |
| Parcel area | 173.25 m² | Land-use confirmation cert. |
Workflow: massing the regulatory envelope
- Set the active option to Main Model. Status bar dropdown (bottom of screen) → select Main Model. Any element placed now belongs to the main model.
- Create a Conceptual Mass family or In-Place Mass. Massing & Site tab → In-Place Mass. Name it Regulatory Envelope.
- Sketch the footprint. Draw the parcel boundary first, then offset inward by the required setbacks (road setback, side setbacks). The resulting polygon is your maximum footprint. Verify: footprint area ÷ parcel area ≤ BCR limit (60%).
- Extrude to the height limit. Extrude the footprint to the absolute height limit (18 m). This is the base regulatory prism.
- Apply the north daylight setback. For the north face: add a void cut that rakes the massing back from the north boundary using the daylight angle formula (1.5 m base + H/2 above 9 m). Use a Reference Plane with the angle locked to a parameter for easy adjustment.
- Check FAR. Use a Revit schedule on the mass floors to sum the gross floor area at each level. Total GFA ÷ parcel area must be ≤ FAR limit (200% = 346.5 m²). Trim the massing vertically if FAR is exceeded before BCR is reached.
- Apply a semi-transparent material. Assign a transparent amber or blue material to the envelope mass so design options placed inside it read clearly against it in 3D.
Drive the envelope with Shared Parameters: BCR_limit, FAR_limit, Height_limit, North_setback. Link them to the mass via a formula. When the planning officer changes a number, update one parameter and the entire envelope regenerates.
04 Creating & populating design alternatives
Switching to an option for editing
- Status bar dropdown → select the option you want to edit (e.g. Mass A — Max Envelope). The active option name appears in the status bar; a blue border frames the viewport.
- All elements you place now belong to that option only. The main-model regulatory envelope remains visible as a reference ghost.
- To switch to a different option, use the dropdown again. Elements from other options are shown in halftone (you can toggle this in Visibility/Graphics).
Typical alternatives for a zoning study
What to model inside each option
- Mass geometry (floors, extrusions, voids) specific to that design proposal
- Mass floors at each level — used by the schedule to calculate GFA per option
- Generic floor/wall components sufficient to read the section and plan strategy
- Do not duplicate shared elements: levels, grids, site topo, regulatory envelope mass
- Structural grid variants can live in a separate option set if they differ between proposals
If two options share identical floor plates at low levels but diverge higher up, model the shared floors in the Main Model and only the divergent upper floors inside the respective options. This avoids double-counting in area schedules.
05 Views, visibility & schedules per option
Assigning a specific option to a view
- Open the view (floor plan, section, 3D view) you want to dedicate to one option.
- Open Visibility/Graphics Overrides (VG or VV) → Design Options tab.
- For each Option Set, choose which option to display in this view: Automatic (shows primary) or a specific named option.
- Duplicate the view for each option, assign the corresponding option, then rename: 3D — Option A Max Density, 3D — Option B Tower Podium, etc.
Dedicated view set for client presentations
| View name | Type | Option shown | Purpose |
|---|---|---|---|
| Site — Regulatory Envelope | 3D | Main model only | Show legal maximum before any design |
| 3D — Option A | 3D | Mass A | Max density proposal |
| 3D — Option B | 3D | Mass B | Tower podium proposal |
| L1 Plan — Option A | Floor plan | Mass A | Ground-floor footprint comparison |
| Section N-S — All options | Section | Automatic (primary) | Height envelope check |
| Area Schedule — All options | Schedule | Filters per option | BCR / FAR comparison table |
Area schedule with option filter
To compare BCR and FAR across all options in a single schedule:
- View tab → Schedules → Schedule/Quantities. Category: Mass. Name: Massing Area Comparison.
- Add fields: Mass Name, Design Option, Gross Floor Area, Number of Floors.
- Add a calculated field: FAR = Gross Floor Area ÷ Parcel Area. Add another: BCR = Footprint Area ÷ Parcel Area.
- Group rows by Design Option. Now each option appears as a sub-group with its own total GFA, FAR, and BCR — all in one schedule.
Place this schedule on a dedicated sheet next to three side-by-side 3D views (one per option). It becomes your entire early-stage design comparison document — no PowerPoint needed for the first client review.
06 Presenting alternatives & accepting the primary option
Sheet set for client design review
- Sheet 1 — Regulatory envelope: site plan + 3D of max buildable prism with BCR/FAR/height labels
- Sheet 2 — Option A: plan, section, 3D + area schedule row for Option A
- Sheet 3 — Option B: same layout, Option B views
- Sheet 4 — Option C: same layout, Option C views
- Sheet 5 — Comparison: three 3D views side by side + full area comparison schedule
Accepting the chosen option
- Client or design team selects Option B (for example) as the direction to develop.
- Go to Manage → Design Options → Design Options dialog.
- Select Mass B — Tower Podium and click Make Primary.
- Click Accept Primary. Revit merges Option B's elements into the Main Model and removes the option set.
- Archive the other options first if you need a record: duplicate the views dedicated to Options A and C into a separate browser folder labeled _Archive — Rejected Options before accepting.
Accepting a primary option permanently deletes all non-primary options and their elements from the file. Save a backup copy of the project file before clicking Accept Primary. Store it as ProjectName_DesignOptions_Archive_YYYYMMDD.rvt.
Post-acceptance: clean-up checklist
- Delete or repurpose views that were dedicated to rejected options
- Update the regulatory envelope mass if the chosen design triggers a different BCR/FAR calculation basis
- Rename the accepted mass from Mass B — Tower Podium to Building Mass
- Run Revit Purge Unused to remove any family types used only in deleted options
- Update the project area schedule to reflect the now-merged single design
→ Quick reference
| Task | Where in Revit | Key action |
|---|---|---|
| Create option set | Manage → Design Options → New (Option Set) | Name: Building Mass Strategy |
| Add an option | Design Options dialog → New (Option) | Name with letter prefix: A — Max Density |
| Switch active option | Status bar dropdown (bottom of screen) | Select option name or Main Model |
| Control view per option | VG → Design Options tab | Set each option set to desired option |
| Build regulatory envelope | Massing & Site → In-Place Mass (Main Model active) | Extrude footprint to height limit, apply setback voids |
| Area comparison schedule | View → Schedules → Category: Mass | Add Design Option field; group by option |
| Make option primary | Design Options dialog → Make Primary | Do this before Accept Primary |
| Accept & merge | Design Options dialog → Accept Primary | Save backup first — irreversible |
Design Options turns your Revit model into a genuine decision-making environment — not just a drawing tool. Used from day one of a project, it keeps the regulatory envelope and every design alternative live, comparable, and in the same file. When the client decides, one click promotes the winner and archives the rest. No file duplication. No copy-paste chaos. No "which version is this?" emails.
Try the workflow on your next project
Start with a single Option Set named "Building Mass Strategy," build the regulatory envelope in the Main Model, and add three options. You'll have a client-ready massing comparison before the end of your first modelling session.
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