(A) Purpose. The purpose of this section is to authorize certain uses of property that are incidental to, and customarily associated with, the principal use, which require standards to manage impacts on the principal and adjacent uses.
(B) Applicability.
(1) Establishment. Accessory uses and structures may only be established or constructed if they meet the standards of this section and all other applicable standards of this Zoning Ordinance. These standards apply when:
(a) Establishment or construction. An accessory use or structure is established or constructed;
(b) Structure expansion. An existing accessory structure is expanded by more than 10% of its gross floor area; and
(c) Use expansion. There is an expansion of the accessory use to or within an existing building, in an outdoor area devoted to the use, or a combination thereof.
(2) Unlisted accessory uses. Refer to § 156.C.010, New and Unlisted Uses, as the same means of interpretation apply to accessory uses as apply to principal uses.
(C) Standards that apply to all accessory uses and structures.
(1) Use. An accessory use or structure may be established provided that it is associated with a primary use permitted in § 156.C.003, Use Table and the associated use category definitions in § 156.M.003, Definitions, and that it complies with the standards of this section. No accessory structure may be used unless the primary structure also is being used.
(2) Subordinate.
(a) An accessory use or structure shall be subordinate to and serve a principal use or structure.
(b) A non-agricultural accessory structure shall be subordinate in height and gross floor area to the principal structure.
(3) Commercial use. Accessory structures located on residentially zoned or used property shall not be used for commercial purposes other than home occupations that comply with this section.
(4) Timing of construction. No detached accessory structure shall be constructed until the construction of the rafters, or general equivalent, of the primary structure has commenced.
(5) Same property and ownership. An accessory use or structure shall be located on the same property and shall be under the same ownership as that of the principal use or structure served.
(6) Separation. No accessory structure shall be located closer than five feet to any other structure.
(7) Setbacks. Accessory structures shall comply with the front, side street, and side setback standards for the primary structure established in Article B, District Development Standards. Detached accessory structures have a minimum rear setback of ten feet and attached accessory structures shall comply with the rear setback that applies to the primary structure.
(8) Height. The maximum height for a residential or nonresidential accessory structure is 18 feet, unless specified within this section.
(9) Easements. Accessory structures permanently affixed to the ground shall not encroach into an easement.
(10) Compatibility. Accessory buildings (in excess of 120 square feet) shall be designed to be compatible with the surrounding neighborhood and shall use building materials as set forth in § 156.D.002, General Requirements.
(D) Decks and patio.
(1) Front yard decks and patios may extend into the required front yard setback ten additional feet.
(2) Rear and side yard decks must comply with the setbacks listed in their respective district.
(3) Fences and screening for decks, patios, pools and other structures on the interior of the yard shall not exceed six feet above the floor or ground level of said structure; provided, they are attached or directly adjacent to the primary building on the lot and meet the underlying primary building setbacks.
(E) Residential accessory uses and structures. Residential accessory uses and structures include dwelling units, sheds for the storage of household items and equipment, garages, pergolas, and similar structures. Except as provided in the standards of this division, the following standards shall apply to residential accessory uses and structures:
(1) Location.
(a) No accessory building or part thereof shall be located in the front yard.
(b) Any accessory building that is not a part of the main building shall be located not less than five feet from any portion of the main building or any other structure on the lot (not including fences).
(2) Front setbacks. Accessory structures shall comply with the front setback standards for the principal structure established in § 156.B.004, Residential District Development Standards.
(3) Dimensional requirements. Residential accessory uses and structures shall comply with the dimensional requirements established in Table 156.C.007-1, Accessory Structure Dimensional Requirements, below.
(4) Side yard setback. Any accessory building located entirely or in part in a side yard shall be erected in conformity with the side yard regulations of the zoning district in which the building is located. On a corner lot in any dwelling district, the width of the yard along the side street line shall not be less than one-half of the depth of the front yard.
(5) Rear lot line. Where the rear lot line of a corner lot is the side lot line of the adjoining lot, the side yard regulations of the district shall apply to the location of the accessory building.
(6) Attached structures. Attached accessory structures, such as attached garages, shall comply with the setbacks of the principal structure.
(7) Storage. Semi-trailers and shipping containers shall not be used for storage in residential zoning districts.
Housing Type | Lot Size | Max. Footprint 1 |
Maximum Floor Area | Minimum Setback2 |
Max. Wall Height | Max. Structure Height |
Housing Type | Lot Size | Max. Footprint 1 |
Maximum Floor Area | Minimum Setback2 |
Max. Wall Height | Max. Structure Height |
Single-Family and Duplex Residencies | 0.5 acre or less | 30% | 1,000 s.f. | 5 ft. | 10 ft. | 15 ft. |
0.5 - 1 acre | 30% | 1,600 s.f. | 5 ft. | 12 ft. | 15 ft. | |
1 - 5 acres | 30% | 3,000 s.f | 5 ft. | 12 ft. | 20 ft. | |
5 acres or more | 30% plus | 5,000 s.f. plus 1,000 s.f. per acre over 5 acres not to exceed 10,000 s.f. | 10 ft. | 14 ft. | 20 ft. | |
Multi-family Residencies (Multiplex, Townhouse, Apartment) | Any Size | 30% | 300 s.f. per unit | 10 ft. | 10 ft. | 15 ft. |
TABLE NOTES: 1 Calculated as a percentage of the permitted rear yard. 2 Minimum setback from property lines when structure located entirely in the rear yard. Refer to § 156.C.007(E) for setback on corner lots. | ||||||
(F) Accessory dwelling units (ADUs). Accessory dwelling units shall be permitted in all residential zoning districts as an accessory use to single-family detached on lots greater than or equal to 15,000 square feet, or the single-family attached housing type in the Mixed-Use (MU) and Urban Core (UC) zoning districts, subject to the following standards:
(1) ADU types. There are two types of ADUs:
(a) Integrated ADUs; and
(b) Detached ADUs.
(2) Integrated ADUs.
(a) Integrated ADUs are located within a permitted building and shall comply with the building placement standards for the permitted and associated principal building type.
(b) Integrated ADUs may be established by dividing space within a principal building (See (A) in Figure 156.C.007-1, below), or by adding floor area to an existing building (See (B), below). Integrated ADUs may be accessed from within the principal building or from outside, according to the standards of this section.
(c) Integrated ADUs appearance:
1. Integrated ADUs shall not involve design modifications to the exterior of the principal building that make their presence obvious.
2. Where exterior doors provide direct access to the integrated unit, such doors shall be designed, located, and configured in a manner that is typical for secondary access to a residential dwelling (e.g. side doors, French doors, etc.).
3. Any exterior stairs that would serve as the primary entrance to the ADU shall be located on the side or rear of the principal structure and are prohibited from being located on the front of the principal structure.
4. If a principal building is expanded to accommodate an integrated ADU, the expansion shall be designed in a manner that is comparable to the principal building.
5. Only one entrance may be located on the front facade of the principal building facing the street unless the building contained additional front entrances prior to the ADU's construction.
(3) Detached ADUs.
(a) Detached ADUs are dwelling units that are located inside of an accessory structure, such as a detached residential garage (See (C) in Figure 156.C.007-1, below) or detached structure (D).
(b) Where an improved alley adjacent to the lot exists, vehicular access to the ADU shall take place from the alley.
(c) Generally, access to second-floor units shall be from internal stairs. External stairs may be permitted where they are not located parallel to an interior side property line or where the Administrator determines that screening features are in place to protect the privacy of an adjacent lot's side yard.
(d) In the RL, RM, RH, and in the Single-Family Attached building type in the Mixed-Use (MU) zoning districts, where a detached ADU is proposed, the owner of the subject property shall live in either the principal residence or the ADU.
(e) Prohibited locations. ADUs may not be established within manufactured homes or structures and vehicles that do not have a permanent foundation, including, but not limited to recreational vehicles, travel trailers, or campers.
(f) Maximum floor area of the ADU.
1. Measurement. The floor area is measured as the area within the ADU itself and does not include areas of an accessory building that are used for other purposes, such as a detached garage or a workshop that is not incorporated into the ADU.
2. Standard. The floor area of an ADU shall not exceed 50% of the total square footage of the principal residential building to which it is accessory, or 1,000 square feet, whichever is less.
(g) Required parking for ADUs. In the RL, RM, and RH districts, in addition to the parking requirements for the principal residential use set out in § 156.E.004, Required Off-Street Parking, one off-street parking space for the ADU shall be provided.
(G) Additional standards for specific accessory uses or structures.
(1) Home-based business.
(a) Permitted home-based businesses. All no-impact home-based businesses are permitted.
(b) Prohibited home-based businesses. The following home-based businesses are considered prohibited:
1. Animal hospitals;
2. Private clubs;
3. Restaurants;
4. Stables and kennels;
5. Automobile repair or auto body shops. More than two vehicles per year that are not registered at the residence and are rebuilt, repaired, or reconstructed shall constitute an automobile repair or auto body shop;
6. Automobile paint shop;
7. Any occupation which is considered illegal by law; and
8. Any use which does not meet the standards in division (G)(1)(d) of this section.
(c) Home-based businesses other than listed above. Any home-based business which is not considered "permitted" or "prohibited" shall use and abide by the special use process as described in Subsec. 156.J.005.1, Special Use Permit, with the exception of a review by the Plan & Zoning Commission. A special fee for a special use permit for a home-based business shall be set by resolution. The Board of Adjustment shall review the home-based business in regards to the standards listed in division (G)(1)(d) of this section. The Board shall take into account concerns by neighbors and the possible negative impacts to the residential character of the neighborhood. The Board may place any restrictions on the home-based business and the Board shall be critical when evaluating requests for additional employees.
(d) Standards for all home-based businesses.
1. Area limitation. The occupation may not exceed 25% of the gross floor area of the principal dwelling.
2. Safety. The occupation may not be more dangerous to life, personal safety, or property than any other activity ordinarily carried on with respect to a dwelling used solely for residential purposes.
3. Non-compliance. Any home-occupation which does not abide by the terms of this section shall be punishable under Article L, Enforcement and Remedies.
4. Modifications or additions. Structural modifications or additions to the residence for the expansion of a home-based business shall be constructed to be compatible with the primary structure and remain residential in appearance.
5. Traffic and parking. Traffic generated by the home-based business shall not be objectionable to the neighboring residents. Off-street parking shall be adequate to accommodate the parking demand generated by the home-based business.
6. Deliveries. The occupation shall not require the delivery or shipment of materials, merchandise, goods, or equipment by other than passenger motor vehicles, one-ton step-up vans, or similar-sized trucks that are less than ten tons gross vehicle weight.
7. Equipment. Any merchandise or stock in trade sold, repaired or displayed shall be stored entirely within the residential structure or in an accessory building.
8. Signs. Any sign utilized by a home-based businesses in a residential district shall be limited to one building-mounted sign which shall not exceed one square foot in area.
9. Residential character. The building or premises occupied shall not be rendered objectionable or detrimental to the residential character of the neighborhood due to exterior appearance or by the emission of dust, gas, noise, odor or smoke, or in any other way.
10. Residential design features. The building shall include no features of design not customary for residential use.
11. No exterior display. No use shall indicate from the exterior any display that the building is being used in part for any purpose other than that of a dwelling, with the exception of permitted signage.
(e) Existing home-based businesses. Existing home-based businesses that are in conformance at the time of adoption of this chapter shall remain in conformance. If an existing business is vacated, any new business must meet current regulations.
(2) Solar panel array (accessory use).
(a) Ground-mounted solar panels. Ground-mounted solar panels shall be:
1. Located in the interior side or rear yard and screened from adjacent residential property and all public rights-of-way with Type B bufferyard (see § 156.F.004, Buffering);
2. Set back from lot lines as if they were detached accessory buildings if the highest point on the panels is more than six feet above grade;
3. Ground-mounted solar panel structures cannot exceed six feet in total height;
4. Application shall be presented with site specifications, dimensions, and landscaping plan; and
5. Not allowed in residential use properties regardless of zone.
(b) Roof-mounted arrays. Roof-mounted solar panels may be located on principal and accessory buildings.
1. A roof-mounted array on a pitched roof may not extend more than 12 inches above the roof surface if the roof is visible from the public right-of-way or from a residential property, nor may it extend more than 12 inches beyond any edge of the roof;
2. Where an array is placed atop a flat roof, it may not extend more than five feet above the roof and shall be screened from the public right-of-way with the building’s facade parapet or similar mechanism;
3. Installed roof-mounted arrays shall meet the International Building Code standards for wind loads; and
4. A roof-mounted solar panel array that cannot meet these placement standards requires a special use permit.
(3) Small wind energy conversion system (SWECS).
(a) General regulations.
1. Other permits required. The owner/operator of the SWECS shall also obtain any other permits required by other federal, state, and local agencies/departments prior to constructing the system.
2. Number of systems per lot.
A. No more than one freestanding SWECS may be placed on any parcel or lot for residential use. Building-mounted SWECS are prohibited on any parcel or lot containing a single-family detached or attached use.
B. No more than one freestanding SWECS may be placed on any parcel or lot with a non-residential use that is taller than the tallest existing principal building located on the parcel or lot. Additional freestanding SWECS which conform to setback requirements contained in this division and which are no taller than the tallest existing principal building located on the parcel or lot may be allowed. Additional building-mounted SWECS may be allowed within the parameters of this section.
C. Any mixed-use building shall be considered a non-residential use for the purposes of this division.
3. Tower. Only monopole towers may be permitted for freestanding SWECS. Lattice, guyed or towers of any other type may not be considered to be in compliance with this division. SWECS towers shall be utilized for the sole purpose of supporting wind energy conversion systems. No other uses may be permitted on SWECS towers.
4. Color. Freestanding SWECS shall be a neutral color such as white, sky blue, or light gray. Building-mounted SWECS shall match the color of the building on which it is mounted. Other colors may be allowed at the discretion of the Board of Adjustment. The surface shall be non-reflective.
5. Lighting. No lights may be installed on the tower, unless required to meet FAA regulations.
6. Signage. No signage or advertising of any kind may be permitted on the tower or any associated structures.
7. Climbing apparatus. The tower shall be designed to prevent climbing within the first ten feet.
8. Maintenance. Facilities shall be well-maintained in accordance with manufacturer’s specifications and shall remain in an operational condition that poses no potential safety hazard nor is in violation of any provisions contained within this division or elsewhere within this Zoning Ordinance.
9. Displacement of parking prohibited. The location of the SWECS shall not result in the net loss of required parking as set out in § 156.E.004, Required Off-Street Parking.
10. Utility notification. The city will notify the utility of receipt of an application to install an interconnected customer-owned generator. Off-grid systems are exempt from this notification requirement.
11. Interconnection. If connected to the grid, the SWECS shall meet the requirements for interconnection and operation as set forth by the utility and the Iowa Utilities Board. No permit of any kind may be issued until the city has been provided with a copy of an executed interconnection agreement. Off-grid systems are exempt from this requirement.
12. Restriction on use of electricity generated. A SWECS shall be used exclusively to supply electrical power to the owner for on-site consumption, except that excess electrical power generated by the SWECS and not presently needed for use by the owner may be used by the utility company in accordance with Section 199, Chapter 15.11(5) of the Iowa Administrative Code, as may be subsequently amended.
13. Shadow flicker. No SWECS may be installed and operated so to cause a shadow flicker to fall on or in any existing residential structure.
14. Safety controls. Each SWECS shall be equipped with both an automatic and manual braking, governing, or feathering system to prevent uncontrolled rotation, over-speeding, and excessive pressure on the tower structure, rotor blades, or turbine components. Said automatic braking system shall also be capable of stopping turbine rotation in the event of a power outage so as to prevent back feeding of the grid.
15. Noise. All SWECS shall not emit more than 60 dB in residential zones and 75 dB in any other zone. This shall be proven through provided engineered specification.
16. Shut off. A clearly marked and easily accessible shut off for the wind turbine will be required as determined by the Building Official of the City of Marshalltown.
17. Electromagnetic interference. All SWECS shall be designed and constructed so as not to cause radio and television interference. If it is determined that the SWECS is causing electromagnetic interference, the owner/operator shall take the necessary corrective action to eliminate this interference including relocation or removal of the facilities, subject to the approval of the city. A permit granting a SWECS may be revoked if electromagnetic interference from the SWECS becomes evident.
18. Wind access easements. The enactment of this division does not constitute the granting of an easement by the city. The SWECS owner/operator shall have the sole responsibility to acquire any covenants, easements, or similar documentation to assure and/or protect access to sufficient wind as may or may not be necessary to operate the SWECS.
19. Engineer certification. Applications for any freestanding or building-mounted SWECS shall be accompanied by standard drawings of the wind turbine support structure, including the tower, base, and footings, or existing structure if applicable. An engineering analysis of all components of the SWECS showing compliance with the applicable regulations and certified by an Iowa licensed professional engineer shall also be submitted.
20. Installation. Installation shall be done according to manufacturer’s recommendations. All wiring and electrical work shall be completed according to the applicable building and electric codes. All electrical components shall meet code recognized test standards.
21. Removal. If a site, or any wind turbine, is not used for a period of one year or is in a state of disrepair as determined by the Zoning Administrator, it shall be the duty and obligation of the party then in possession and control of the site to have the unused structure completely dismantled and removed from the site.
22. Right of entrance. As a condition of approval of a special use permit, an applicant seeking to install SWECS is required to sign a petition and waiver agreement which shall be recorded and run with the land granting permission to the city to enter the property to remove the SWECS pursuant to the terms of approval and to assure compliance with the other conditions set forth in the permit. Removal will be at the expense of the owner/operator and the cost may be assessed against the property.
23. Feasibility study. A feasibility study shall be made of any site prior to installing a wind turbine. The feasibility study shall include measuring actual wind speeds at the proposed turbine site for at least three months.
(b) Bulk regulations.
1. Setbacks. The minimum distance between any freestanding SWECS and any property line shall be a distance that is equivalent to:
A. One hundred fifty percent of the total system height for towers up to 65 feet in height.
B. Two hundred percent of the total system height for towers that are 65 feet and up to 80 feet in height.
C. Two hundred fifty percent of the total system height for towers that are 80 feet and up to 100 feet in height.
D. Three hundred percent of the total system height for towers that are 100 feet and taller in height.
E. The setback shall be measured from the property line to the point of the SWECS closest to the property line.
F. The required setback for any building-mounted SWECS shall be equal to the required setback of the principal building to which the SWECS is to be attached at such time that the application to install a building-mounted SWECS is received by the city.
(c) Maximum height. Height is measured from the ground to the top of the tower, including the wind turbine generator and blades.
1. For lots of more than three and fewer than five acres, the maximum height shall be 65 feet.
2. For lots of five and up to 40 acres, the maximum height shall be 80 feet.
3. For lots of 40 acres and up to 100 acres, the maximum height shall be 100 feet.
4. For lots that are 100 acres and larger, the maximum height shall be 140 feet.
5. Building-mounted SWECS may be a maximum of ten feet higher than the point of attachment to the building on which they are attached.
(d) Minimum lot size.
1. The minimum lot size for a freestanding SWECS is three acres.
2. The minimum lot size for a building-mounted SWECS is one acre for any building of less than five stories in height.
3. There is no minimum lot size for building-mounted SWECS to be mounted on buildings of five or more stories in height.
(e) Blade length. The length of each individual blade may not exceed 50% of the height of the tower.
(f) Clearance of blade. No portion of a horizontal axis SWECS blade may extend within 30 feet of the ground. No portion of a vertical axis SWECS may extend within ten feet of the ground. No blades may extend over parking areas, driveways or sidewalks. No blade may extend within 20 feet of the nearest tree, structure or above ground utility facilities.
(g) Location. No SWECS shall be located less than 50 feet from any other SWECS.
1. No part of a SWECS may be located within or over drainage, utility or other established easements.
2. A freestanding SWECS shall be located entirely in the rear yard for residential uses. For a freestanding SWECS for all other uses, the location shall be appropriate to the property and setting and shall be determined through the special use permit and site plan review process.
3. A SWECS shall be located in compliance with the guidelines of applicable Federal Aviation Administration (FAA) regulations as amended from time to time.
4. No SWECS may be constructed so that any part thereof can extend within 20 feet laterally of an overhead electrical power line (excluding secondary electrical service lines or service drops). The setback from underground electric distribution lines shall be at least five feet.
5. Building-mounted SWECS are prohibited unless the owner has obtained a written analysis from an Iowa licensed structural engineer determining that installation of a SWECS will not cause damage to the structure and that the SWECS can be securely fastened so as to not pose a hazard caused by detaching from the structure.
(Ord. 15039, passed 4-11-2022; Ord. 15085, passed 7-8-2024)