Residential Accessory Structure Guide

This guide page outlines the minimum documentation necessary to allow a permit application for the construction, alteration or repair of a detached structure accessory to an existing single-family, duplex, triplex or townhome building, such as a pergola, carport, shed, garage, studio, or accessory dwelling unit to be taken in for review. Applicants may be required to submit additional information as necessary to clearly demonstrate compliance with all applicable codes. Please be advised that incomplete applications, or plans that do not meet the submittal requirements will not be accepted for review.

Detached sheds, pergolas and other structures smaller than 80 square feet, shorter than 10 feet in height, with no electrical, plumbing, or mechanical equipment do not require a building permit but are required to meet all applicable code requirements, including meeting accessory building setbacks. Please note that no structure may be placed in an easement, even if it does not require a building permit. All new structures in flood zones and/or wetlands require a floodplain development permit and/or a wetland development permit even if the structure does not require a building permit. All new structures in historic districts require a Landmark Alteration Certificate, even if the structure does not require a building permit

• Scope of Work Form (complete the city form)
• Stormwater & Flood Management Plant Investment Fee Calculation Form (if there is no change in the impervious area of the property, please check the” No Change to Impervious Area” box)
• Site Survey (stamped by a Colorado Licensed Land Surveyor)
  • See the Land Survey Informational Handout to determine which type of survey will be required for your project scope.
  • Include topographical contours if the lot has a slope greater than 1:25 (4% slope, or 2.3°) within 25 feet of the proposed structure location and the proposed structure is 11 feet or taller in height.

• Zoning Data Worksheet (required for structures with less than 50% open roof framing)
• Lot Area Declaration Form (required for structures with less than 50% open roof framing)
• Housing, Development Excise Tax and Impact Fee Worksheet

The following permits, approvals and supplemental information may be required based on scope of the project and/or the location and development constraints of the property:

• Asbestos Inspection Report (required if disturbing potentially asbestos-containing materials, at the following trigger levels: 32 SF of surfaces; 50 linear feet of pipes; or creating waste equal in volume to a 55- gallon drum)
• Plumbing Fixture Count and Irrigation Form (required for all plumbing scopes of work)
• Historic Approval (Demolition Review of buildings more than 50 years of age when the work meets the definition of demolition in B.R.C. (1981) Section 9-16 or Landmark Alteration Certificate required for exterior alterations in a Historic Preservation District or for Individual Landmarks)
• Floodplain Development Permit (required for structures located in a regulatory floodplain)
• Stream, Wetland and Water Body Permit (required for structures located in a regulatory wetland)
• Grading and Drainage Plan (required for structures located on a steep slope or area of mass movement)
• Soils Report (required for structures located in an area of a steep slope or area of mass movement)
• Wildland-Urban Interface Code compliance information (required for structures located in the urban interface zone)
• Previous Approvals (Notice of Disposition and a copy of any city-stamped approval(s) required prior to the review and approval of this application, such as a Variance, Accessory Dwelling Unit Approval, Minor Modification or Site Review)
  • Exterior modifications to properties regulated by a Planned Unit Development (PUD) or Site Review may require an additional review process such as an Administrative Review for a Minor Modification or other development review process may be required. If your property is zoned RL-2, there is a good chance that this applies to your property.
  • Records of past City of Boulder approvals can be requested through pdsrecordrequest@bouldercolorado.gov. If after researching your property history, you are unsure if a Minor Modification is required for your scope of work, please submit a request to our Property Use & Design (Regulations) team.

• Prescriptive Measures Checklist (required for conditioned structures less than 500 square feet, integrated into plan set) 
• Energy Rating Index Report (e.g. HERS) (required for conditioned structures of 500 square feet or more) 
• Heating and Cooling Equipment Sizing (ACCA Manuals) (required for any new mechanical heating and/or cooling systems

• Prescriptive Measures Checklist (required for conditioned structures less than 500 square feet, integrated into plan set) 
• Energy Rating Index Report (e.g. HERS) (required for conditioned structures of 500 square feet or more) 
• Heating and Cooling Equipment Sizing (ACCA Manuals) (required for any new mechanical heating and/or cooling systems
  • Site Plan
    • Include north arrow and all existing and proposed structures.
    • Indicate distances to property lines from existing and proposed structures. Please identify the setback requirements for accessory buildings in your zoning district. Required minimum setbacks may be found in B.R.C. Section 9-7-1. To determine your zoning district, go to the City of Boulder eMaplink webpage, turn on the zoning layer, and enter the property address in the search bar.

    • Accessory structure setbacks for common residential zones are provided below.

      Residential Zoning District		Rl-1, Rm-2, RMX-1	Rl-2, RM-1	RR-2, RE	RR-1
      Minimum Setback	Front Property Line	55 Feet	55 Feet	55 Feet	55 Feet
      	Rear Property Line*	0 or 3 Feet	0 or 3 Feet	0 or 3 Feet	0 or 3 Feet
      	Interior Side Property Line*	0 or 3 Feet	0 or 3 Feet	10 Feet	15 Feet
      	Side Yard Adjacent to a Street**	12.5 Feet	10.5 Feet	25 Feet	25 Feet

      *If the structure is to be built at the 0 setback to an interior side or rear property line that does not back to an alley or street, a maintenance easement agreement with the affected neighbor that has been recorded with the Boulder County Clerk and Recorder must be submitted at the time of building permit application.

      **On corner lots the setback for a side yard adjacent to a street may be the same as a front yard setback if the neighboring property fronts on the street. Please submit an inquiry to verify setbacks.

      NOTE: Structures that are attached to the principal building (dwelling or residence) are considered additions to the principal building and must meet principal building setbacks

    • Indicate distances between all structures on the lot, 6 feet minimum separation is required between buildings. Structures with more than 50% open roof framing are considered to be structures and do not need to meet building separation requirements as required in B.R.C. Section 9-7-1.
    • Indicate the proposed height of the structure, measured from the low point 25 feet away from the structure.
    • For properties within the RR-1, RR-2, RL-1, RE and MH zoning districts, include a solar analysis if the structure exceeds 12 feet in height. Refer to the Solar Access Guide to determine requirements for other zone districts and for information about how to prepare the analysis.
    • Show the location and extent of any easements on the site plan. No structures or any portion of a structure (such as a roof eave) can encroach into an easement.
    • Indicate the location and extent of any flood zones and regulated wetlands, if applicable.
  • Floor Plans and Building Elevations
    • Provide the floor area in square feet of the proposed structure, measured to the outside surface of the exterior walls or vertical elements.
    • Elevation drawings showing the locations and sizes of any windows and doors, as well as indicating building height. Note that openings on walls parallel to interior side lot lines are prohibited if at the 0 setback and limited to 25% of the wall area if less than 5 feet from the lot line.
    • Stair and landing details, if applicable.
    • Location(s) of electrical services, main and subpanels if wiring the structure for electrical service. Indicate if feeds are underground or overhead.
  • Structural Drawings (stamped by a Colorado Professional Engineer)
    • Framing Plans showing the wood species, grade, size, spacing and span of floor joists, wall studs, roof rafters and any other relevant framing systems. Indicate whether wood has been pressure treated with a wood preservative.
    • Connection details and fastener information for all joists, girders, posts, rafters, and other structural elements.
    • Fire-resistive assemblies are required for structures within 5 feet of a property line. Projections such as eaves cannot extend closer than 2 feet from a property line and must have a 1-hour fire-rated assembly if the vertical wall of the structure is within 5 feet of a property line.
    • Footing and foundation design details.
    • Roofing slope and material details. Please indicate how Class A roof assembly requirements are being met.

May Be Required

• Mandatory Measures Checklist (required for structures with heating and/or cooling)
• Solar Access Plan (required for structures that exceed the solar fence height identified in B.R.C. Section 9-9-17)
• Landscape Plan (required for new enclosed structures where the valuation exceeds 25% of the existing structure)