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Stephen Sparn Architects,PC


BOULDER'S COMPATIBILITY ORDINANCE

Going in for a building permit on a project in Boulder?
SSA is your one-stop shop for complying with Boulder's new Compatibility Ordinance.

After nearly two years of citywide surveys, public debates, consultant research, negotiations and political maneuvering, the "compatible development" ordinance that sets limits for how big houses can be built has officially become a part of Boulder's Land Use code.

The changes put limitations on building height, floor area, unsightly expanses of side walls, and the coverage that buildings take up on any given lot.

Affected Properties and Zone Districts

  • All principal and accessory residential buildings in the RR-1, RR-2, RE, RL-1, portions of RL-2 zone districts
  • All principal and accessory single-family buildings in the RMX-1 zone districts.
  • For properties located in Planned Developments, Planned Residential Developments, or Planned Unit Developments within these zones, the more restrictive provisions apply.
  • Properties with annexation agreements that have house size restrictions are not subject to Compatible Development.
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Side Yard Bulk Plane

A bulk plane determines the three-dimensional building envelope for a lot. The Compatible Development bulk plane begins at the side property line at 12 feet in height and then slopes inward at a 45 degree angle allowing one foot of additional height for every one foot of setback up to the maximum building height.

Allowed Side Yard Bulk Plane Encroachments

Encroachments are permitted within the bulk plane for the following main architectural features:

  1. Roof overhangs or eaves of the primary roof that do not extend more than 30 inches horizontally beyond the bulk plane.
  2. Rooftop solar systems that are either flush-mounted or mounted at up to a 15-degree angle measured from the horizontal plane.
  3. Gable end of a sloping roof form that is 40-feet in width and that does not extend more than eight feet beyond the bulk plane.
  4. Dormers with specific height and width requirements.

An additional encroachment into the bulk plane may be granted for individual landmarks and buildings within historic districts, if found necessary and historically appropriate through the Landmark Alteration Certificate process.

Side Yard Bulk Plane Exemptions

The following exemptions are allowed to the bulk plane:

  1. Lots that are less than 4,000 square feet and lots that are less than 45 feet average in width.
  2. Lots that have an interior side yard adjacent to a nonresidential use or a multi-family structure for the length of the nonresidential use or multi-family structure
  3. The RL-2 zone is not required to follow the new Compatible Development bulk plane requirements. The RL-2 zone has an existing bulk plane requirement in the Boulder Revised Code which allows two feet of height for every one foot of setback from the property line

Solar Access Ordinance and Bulk Plane

Building permit applications must still comply with the Solar Access Ordinance. With the adoption of the new Compatible Development bulk plane, the two must work together on a property.

Side Yard Wall Articulation

The intent of the wall articulation standards is to help mitigate looming walls and privacy impacts on adjacent properties. The Compatible Development ordinance requires that walls taller than 14 feet in height and within 20 feet of the side property line be limited to a cumulative wall length of 40 feet. If a wall is longer than 40 feet, it must either be setback from the property line by 14 feet or it must reduce in height to 14 feet or less.

Maximum Building Coverage

Building coverage is the percentage of the lot that can be occupied by principal and accessory buildings. The Compatible Development ordinance determines building coverage on a sliding scale starting at 35 percent for a 7,000 square feet lot for all districts. Maximum building coverage increases from 35 percent as lot sizes get smaller than 7,000 square feet and decreases as lot sizes get larger. However, in the RL-2 zone, the building coverage maximums only apply to lots that are 8,000 square feet or larger.

Floor Area Ratio (FAR) Requirements:

The FAR standard is used to relate building size to lot size and to address mass and scale for neighborhood compatibility.. FAR is defined as the ratio of the floor area of a building to the area of the lot on which the building is situated.

The Compatible Development ordinance determines FAR on a sliding scale starting at 0.50 for a 7,000 square feet lot for the RR-1, RR-2, RE, RL-1, and RL-2 districts. The allowed FAR increases as lot sizes get smaller than 7,000 square feet and decreases as lot sizes get larger. However, in the RL-2 zone, the FAR maximums shall only apply to lots that are 8,000 square feet and larger. The sliding scale for the RMX-1 zone is based on 0.55 FAR on a 7,000 square foot lot.


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