Zoning And Codes

4. Building Envelope Controls

Building envelope controls define the three-dimensional volume within which a building may be constructed. These are the most precise regulatory tools in a zoning code.

4.1 Height Controls

4.2 Setback and Build-to-Line Controls

Build-to-line (BTL) is fundamentally different from a setback. A setback defines a minimum distance from which a building must be placed; a BTL defines a line at which the building facade must be placed. The BTL creates a consistent streetwall. The "compliance percentage" specifies how much of the lot width must have building facade at the BTL (the remainder may be recessed for courtyards, forecourts, or entries).

4.3 Lot Coverage

Maximum percentage of the lot area that may be covered by the building footprint:

• T3: 30-50% (significant open space on lot)
• T4: 50-70% (moderate open space)
• T5: 70-90% (minimal open space, may be on upper levels)
• T6: 80-100% (nearly full lot coverage, open space on rooftops or at upper setbacks)

Coverage calculations typically include: all roofed structures, covered porches and galleries (if enclosed on three sides), but exclude: uncovered terraces, pergolas (if less than 50% covered), at-grade patios, underground structures.

4.4 Floor Area Ratio (FAR)

FAR = Total Floor Area / Lot Area. This controls the overall bulk and density of development.

FAR calculation inclusions: all enclosed floor area measured to outside face of exterior walls, mezzanines, occupied basements, enclosed balconies. FAR calculation exclusions: structured parking (often excluded to encourage structured over surface parking), mechanical rooms, unenclosed balconies, residential storage rooms below 5 sqm, ground-floor retail in mixed-use buildings (incentive exclusion in some codes). FAR bonuses: additional FAR may be earned through provision of affordable housing (+0.5-2.0 FAR), public open space (+0.5-1.0 FAR), transit infrastructure contributions (+0.5 FAR), LEED/green certification (+0.5 FAR), heritage preservation (+0.5-1.0 FAR). Bonuses are typically capped and cannot exceed the maximum FAR.

4.5 Sky Exposure Plane

The sky exposure plane is an angular plane that limits building height above a certain base height at the street setback line. It ensures daylight and sky access at the street level.

• Base height: the height at the setback line at which the angular plane begins (typically the streetwall height: 12-24m depending on zone)
• Angle: the angle of the plane measured from the horizontal at the setback line (typically 70-80 degrees from horizontal, or equivalently a slope of approximately 2.5:1 to 5.7:1)
• Application: the building may not penetrate the sky exposure plane on any street-facing facade
• Calculation: at any point along the facade, maximum height = base height + (distance from setback line x tangent of angle)
• Exemptions: mechanical bulkheads, elevator overruns, and architectural features (if within permitted exceptions)

Example: Base height 18m, angle 75 degrees from horizontal. At 5m setback from facade line: max height = 18 + (5 x tan75) = 18 + 18.7 = 36.7m.

4.6 Step-Back Requirements

Step-backs require upper portions of a building to be set back from the lower streetwall facade, reducing the visual bulk of taller buildings and preserving the pedestrian-scale streetwall experience.

• Streetwall height: the height at which the step-back occurs (typically 4-6 stories, or 15-22m)
• Step-back depth: the minimum horizontal distance the upper floors must be set back from the streetwall facade (typically 3.0-6.0m)
• Application: required on all street-facing facades (may not be required on alley-facing or interior facades)
• Rationale: preserves the 1:1 to 1:2 street-width-to-building-height ratio at the pedestrian level, which research identifies as the most comfortable enclosure ratio for urban streets

4.7 Tower Separation

For buildings with tower elements (above the podium/streetwall), minimum separation distances prevent a canyon effect and ensure light, air, and privacy.

• Tower-to-tower (same site): minimum 24m face-to-face
• Tower-to-tower (adjacent sites): minimum 24-30m center-to-center
• Tower floor plate: maximum 750-2,000 sqm (varies by zone; smaller plates improve light penetration and reduce wind effects)
• Tower lot coverage: maximum 40-50% of lot area (the tower footprint, not the podium footprint)
• Point tower preferred: slender towers with floor plates under 1,000 sqm minimize shadow, wind, and view impacts

4.8 Lot Dimensions

Maximum lot and block dimensions prevent superblocks and ensure a fine-grained, walkable urban fabric with frequent cross-streets, mid-block passages, and varied building frontages.

5. Code Generation Workflow

This section provides a step-by-step process for producing a form-based code from a masterplan or area plan. Follow these steps sequentially.

Step 1: Define Character Areas and Transect Zones

• Walk the site and surrounding context (or analyze the masterplan if greenfield)
• Identify distinct character areas based on intended density, use mix, building scale, and street type
• Assign a transect zone (T1-T6) to each character area
• Document the rationale for each zone assignment
• Map zone boundaries on the regulating plan base (parcel map or block map)
• Ensure transitions are gradual (do not jump from T2 to T5 without intermediate zones)

Step 2: Assign Building Form Standards

• For each transect zone, calibrate the dimensional standards (height, setback/BTL, coverage, FAR)
• Select permitted building types for each zone
• Define building disposition (edgeyard, sideyard, rearyard, courtyard) for each zone
• Set ground-floor height minimums (especially for zones requiring commercial ground floors)
• Define step-back requirements for zones permitting buildings above 4-6 stories
• Specify tower controls (floor plate, separation, coverage) for T6

Step 3: Define Frontage Types

• For each transect zone, select the permitted and required frontage types
• Specify dimensions (depth, height, setback) for each frontage type
• Identify required retail frontage streets (where shopfront frontage is mandatory)
• Illustrate each frontage type with a section drawing and photograph (or described equivalent)
• Define the relationship between frontage type and the sidewalk/furnishing zone

Step 4: Create Thoroughfare Standards

• Classify every street in the plan area by type (boulevard, avenue, commercial street, neighborhood street, alley, etc.)
• Assign a cross-section to each street type (use the Street Design skill for detailed specifications)
• Specify ROW width, travel lanes, parking, bike facilities, sidewalk zones, median, planting, and lighting for each type
• Map thoroughfare types to the regulating plan

Step 5: Write Public Space Standards

• Identify all civic spaces in the masterplan (plazas, greens, squares, parks, playgrounds, community gardens)
• Assign a civic space type to each
• Specify minimum size, character, required elements, and programming for each
• Define the relationship between civic spaces and adjacent transect zones (e.g., a plaza must be fronted by T5 or T6 with shopfront frontage)

Step 6: Draft Regulating Plan

• Combine all layers onto a single regulatory map: transect zones, thoroughfare types, civic space locations, special district boundaries, required retail frontage lines, build-to lines
• The regulating plan is the applicant's primary reference -- it must be clear, unambiguous, and at a scale that shows individual parcels
• Include a legend that keys to the code text for all standards
• Provide both a full-area regulating plan and enlarged sub-area plans for complex zones

Step 7: Add Administrative Procedures

• Define the review process: by-right approval (administrative, no hearing) for projects that comply with all standards; design review (staff or board) for warrants (minor deviations); variance process for hardship cases
• Specify which deviations are warrants (minor, staff-approved) versus variances (significant, board-approved)
• Define the submittal requirements: site plan, building elevations, floor plans, landscape plan, signage plan
• Establish a pre-application conference process for large projects
• Include a nonconformities section (existing buildings that do not comply with the new code)

Step 8: Create Design Guidelines Companion Document

• Produce an illustrated, advisory companion document that shows the intent and aspirations of the code
• Include precedent photographs, rendered streetscapes, and annotated diagrams
• Cover topics that are difficult to regulate by code: color palettes, material quality, landscape character, architectural style compatibility
• This document informs applicants, guides design review, and builds community understanding
• Design guidelines are advisory, not mandatory -- they supplement the code but do not override it

6. Output Format

When producing a zoning analysis or form-based code, deliver the following specification package:

Zoning Analysis Output Template

SITE: [Address / Location]
EXISTING ZONING: [Current zone designation]
PROPOSED ZONING: [Proposed zone designation, if applicable]

DIMENSIONAL STANDARDS:
+-----------------------+----------+-----------+
| Parameter             | Required | Proposed  |
+-----------------------+----------+-----------+
| Max Height (stories)  |          |           |
| Max Height (meters)   |          |           |
| Front Setback / BTL   |          |           |
| Side Setback          |          |           |
| Rear Setback          |          |           |
| Lot Coverage (max %)  |          |           |
| FAR (max)             |          |           |
| Open Space (min %)    |          |           |
| Parking Requirement   |          |           |
+-----------------------+----------+-----------+

PERMITTED USES:
- Residential: [list]
- Commercial: [list]
- Institutional: [list]
- Other: [list]

BUILDING TYPES PERMITTED:
- [list with max dimensions for each]

FRONTAGE TYPES REQUIRED/PERMITTED:
- [list with dimensions]

SPECIAL CONDITIONS:
- [overlays, special districts, historic designations, etc.]

DEVELOPMENT CAPACITY:
- Lot area: [sqm]
- Buildable area (coverage): [sqm]
- Maximum floor area (FAR): [sqm]
- Estimated dwelling units: [range based on unit size assumptions]
- Estimated commercial area: [sqm, if applicable]

COMPLIANCE NOTES:
- [List any variances or warrants that would be required]
- [List any additional approvals needed (design review, environmental, etc.)]

Form-Based Code Output Template

FORM-BASED CODE: [Project / Plan Area Name]
JURISDICTION: [City, State/Province, Country]
DATE: [Draft date]
VERSION: [Version number]

ARTICLE 1: GENERAL PROVISIONS
- Purpose and intent
- Applicability
- Relationship to other codes
- Definitions

ARTICLE 2: REGULATING PLAN
- [Map with zone designations]
- Zone descriptions and intent

ARTICLE 3: BUILDING FORM STANDARDS
- [Table for each zone: T3, T4, T5, T6]
- Building type specifications
- Building disposition standards

ARTICLE 4: FRONTAGE TYPE STANDARDS
- [Table for each frontage type]
- Illustrations and dimensions

ARTICLE 5: PUBLIC SPACE STANDARDS
- [Specifications for each civic space type]
- Landscape standards

ARTICLE 6: THOROUGHFARE STANDARDS
- [Cross-sections for each street type]
- Intersection standards

ARTICLE 7: PARKING STANDARDS
- Parking requirements by zone and use
- Bicycle parking requirements
- Design standards for parking structures

ARTICLE 8: SIGNAGE STANDARDS
- Sign types by zone
- Dimensional standards
- Illumination standards

ARTICLE 9: ADMINISTRATION
- Review procedures
- Warrants and variances
- Nonconformities
- Definitions

7. Reference Links

Primary Standards and Model Codes

• SmartCode v9.2 (Center for Applied Transect Studies): https://transect.org/codes.html
• Miami 21 Form-Based Code: https://www.miami21.org/
• Denver Form-Based Code (Zone Districts): https://www.denvergov.org/Government/Agencies-Departments-Offices/Community-Planning-and-Development/Denver-Zoning-Code
• Form-Based Codes Institute (FBCI): https://formbasedcodes.org/
• Congress for the New Urbanism (CNU): https://www.cnu.org/
• Duany Plater-Zyberk & Company (DPZ CoDesign): https://www.dpz.com/

Supplementary Resources

• American Planning Association (APA) Zoning Practice: https://www.planning.org/zoningpractice/
• Lincoln Institute of Land Policy: https://www.lincolninst.edu/
• Urban Land Institute (ULI): https://uli.org/
• National Association of City Transportation Officials (NACTO): https://nacto.org/
• ITDP TOD Standard: https://www.itdp.org/publication/tod-standard/
• PlaceMakers Code Study Collection: https://www.placemakers.com/
• Project for Public Spaces (PPS): https://www.pps.org/

Foundational Texts

• Duany, Plater-Zyberk, Alminana. The New Civic Art: Elements of Town Planning. Rizzoli, 2003.
• Parolek, Parolek, Crawford. Form-Based Codes: A Guide for Planners, Urban Designers, Municipalities, and Developers. Wiley, 2008.
• Talen, Emily. City Rules: How Regulations Affect Urban Form. Island Press, 2012.
• Barnett, Jonathan. Redesigning Cities: Principles, Practice, Implementation. APA Planners Press, 2003.
• SmartCode Manual v9.2. Center for Applied Transect Studies, 2009.