HomeMy WebLinkAboutA002 - Council Action Form dated June 24, 2025ITEM #:45
DATE:06-24-25
DEPT:P&H
SUBJECT:AMENDMENTS TO CHAPTER 29 AND CHAPTER 13 OF THE AMES
MUNICIPAL CODE REGARDING ACCESSORY DWELLING UNITS
COUNCIL ACTION FORM
BACKGROUND:
Earlier this year, the Iowa General Assembly passed Senate File 592, which preempted local
regulations pertaining to Accessory Dwelling Units (ADUs). The bill was signed into law by
Governor Reynolds on May 1, 2025, and comes into effect on July 1, 2025. The minimum
requirements of the state law necessitate changes to our local zoning standards.
Fundamentally, the law intends to permit ADUs on single-family residence lots in a manner
similar to that of a single-family dwelling.
The legislation defines an accessory dwelling unit as: "an additional residential dwelling unit
located on the same lot as a single family residence that is either attached to or detached from
the single family residence." A single family residence defined by the state corresponds to
one- and two-family homes as defined in the Ames Zoning Ordinance.
The City Council initiated changes regarding ADUs at its May 27 meeting and included a
change to require ADUs to meet full rear yard setback (20 feet in lieu of 3 feet). This rear yard
change was due to the increased size and height allowances under the state law.
Significant aspects of the proposed ordinance that address required changes include
increased maximum size from 900 square feet to a maximum of 1,000 square feet or 50% of
the size of the single-family residence, whichever is greater.
Staff proposes within the new ordinance to define size by the definition of Gross Floor
Area in Article 2 of the Zoning Ordinance: the sum of the gross horizontal area of floors
of a building, including interior balconies and mezzanines. All horizontal dimensions
are to be between the exterior faces of walls or from the center line of walls separating
two buildings. Staff believes this is the most easily implemented option, compared to
habitable area and net floor area options and aligns with the state law.
The Zoning Ordinance has minimum design standards for two-family dwellings (duplexes).
The new ADU code applies the design standards to attached ADUs when both doors of the
single-family residence and the ADU face the street.
The ADU ordinance continues to require ADUs to be of new construction, either attached or
detached as allowed by state code. It does not allow for the conversion of an existing home
into two dwelling units. The proposed ordinance does allow for conversion of accessory
structures to an ADU if the structure meets all ADU setback and other requirements that would
otherwise apply. For example, a garage in the rear yard that meets all setbacks could be
converted, but a garage with a reduced rear yard setback below 20 feet that applies to ADUs
would not be eligible for a conversion to an ADU.
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Changes to Chapter 13 are clean-up items to align definitions and ownership requirements
with the state law. The Near Campus Neighborhood Occupancy limitation will still apply, which
limits rental occupancy for properties with increased or additional bedrooms since 2018.
Although no parking can be required for the ADU, the standard includes the requirements that
the minimum parking of two spaces per single family residence must exist to have an ADU.
A full listing of ADU standards is described in the Addendum. The complete draft ordinance is
attached.
PUBLIC NOTICE
The text amendment was reviewed at separate meetings by both the Historic Preservation
Commission and the Planning and Zoning Commission. Both Commissions recommended
approval with no changes to the staff proposal. The public hearing notice was published in
the newspaper.
ALTERNATIVES:
1. Adopt the regulations for Accessory Dwelling Units based upon the proposed changes
as shown in Attachment A. Suspension of the rules is requested to pass the
ordinance on second and third readings and adopt it.
2. Adopt regulations for Accessory Dwelling Units with modified standards.
3. Refer the item back to staff for more information.
CITY MANAGER'S RECOMMENDED ACTION:
The attached ordinance includes revisions needed to comply with the new state statute
for Accessory Dwelling Units, which comes into effect on July 1 of this year. The
revised standards require ADUs to be regulated like single-family residence for most
development standards (setbacks, lot size, etc.) and removes requirements such as
owner-occupancy to rent out the ADU. The proposed ordinance changes are consistent
with Council's prior direction to remove the accessory building exception to setbacks
for ADUs. Therefore, it is the recommendation of the City Manager that the City Council adopt
Alternative No. 1, as described above.
ATTACHMENT(S):
Addendum.pdf
Final Ordinance ADUs Standards.PDF
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Addendum
Senate File 592 regulates how cities and counties in Iowa can regulate Accessory
Dwelling Units. The law aims to regulate ADUs similarly to single-family residences.
Among things, the new legislations states that:
- Accessory dwelling units shall not exceed 1,000 square feet or 50% of the size of
the single-family home.
- ADUs can be limited by historic building restrictions, though they must be in line
with single-family residential requirements for historic structures and/or districts.
- Requirements for ADUs cannot be more restrictive than those imposed on single -
family residences, including:
o Maximum height
o Minimum setbacks
o Minimum lot sizes
o Minimum building frontages
o Maximum lot coverages
o Density
o Aesthetic or architectural standards
- The ADU cannot be required to match the exterior design, roof pitch, or finishing
materials of the single-family residence.
- ADUs cannot be restricted as rental units.
- ADUs cannot be required to have additional parking beyond that of the primary
dwelling.
- Restrictions cannot be placed on ADUs for owner-occupancy, consanguinity, or
age.
Council gave direction to staff in May to bring the setbacks for ADUs into line with that of
single-family residences on the same lot. Staff incorporated that direction into the
proposed ordinance and made several other changes using the existing ADU ordinance,
adopted in January 2024, as a framework. Proposed changes to the Zoning Ordinance
include:
- Changes to setbacks to conform with primary dwellings. Current regulations allow
ADUs to have reduced rear setbacks (3 feet) in line with other accessory
structures. The new regulations will treat ADUs and single-family residences the
same.
- Change the size from a maximum of 900 square feet, currently the same as other
accessory structures, to allow for a maximum of 1,000 square feet or 50% of the
size of the house. Size is proposed to be defined according to the definition of
Gross Floor Area in the Zoning Ordinance:
the sum of the gross horizontal area of floors of a building, including interior
balconies and mezzanines. All horizontal dimensions are to be between the
exterior faces of walls or from the center line of walls separating 2 buildings.
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- Remove restrictions that ADUs can only be rented when the owner resides on the
site.
- Remove the requirement for ADU on-site parking.
- Clarify that ADUs are allowed on a property with a duplex as required by state law.
- Clarify the rear yard coverage for accessory structures would not apply because
of the new setback requirement (currently capped at 25% of the total rear yard
area).
- Adding a design requirement that if there are two doors facing the street must
comply with standards of the City’s two family requirements.
- Only new construction of attached ADUs is permitted, no conversion of existing
area.
- Conversion of an existing detached structure will only be permitted if it complies
with zoning standards.
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ORDINANCE NO.
AN ORDINANCE TO AMEND THE MUNICIPAL CODE OF THE CITY OF
AMES, IOWA, BY AMENDING SECTIONS 13.100(5), 13.201, 13.300(1),
13.503(4)(e)(iii), 29.201(5)(6), TABLE 29.406(2), 29.408(7), AND 29.409,
THEREOF, FOR THE PURPOSE OF AMENDING RENTAL HOUSING AND
ZONING STANDARDS FOR ACCESSORY DWELLING UNITS (ADUs)
REPEALING ANY AND ALL ORDINANCES OR PARTS OF ORDINANCES
IN CONFLICT TO THE EXTENT OF SUCH CONFLICT; AND
ESTABLISHING AN EFFECTIVE DATE.
BE IT ENACTED, by the City Council for the City of Ames, Iowa, that:
Section One. The Municipal Code of the City of Ames, Iowa shall be and the same is hereby amended by
amending sections, 13.100(5), 13.201, 13.300(1), 13.503(4)(e)(iii), 29.201(5)(6), Table 29.406(2), 29.408(7) and
29.409 as follows:
“CHAPTER 13, RENTAL HOUSING
* * *
Sec. 13.100. GENERAL
* * *
(5)Exceptions. The following residential structures are exempt from these rules:
(a) owner-occupied single-family dwellings (see definition of “Owner-Occupied Dwelling Unit”
in Section 13.201).For purposes of this exception, an Accessory Dwelling Unit (ADU) is considered part of the
single-family dwelling so long as both dwelling units are owner occupied.
* * *
Sec. 13.201. TERMS DEFINED
* * *
DWELLING UNIT, ACCESSORY. Accessory Dwelling Unit (ADU) is defined and permitted through standards
of the Zoning Ordinance as a detached or attached “dwelling unit” on the same property as a single-family dwelling
residence.
* * *
Sec. 13.300. GENERAL
(1) Registration required. No owner or operator shall rent, or offer for rent, any dwelling unit for use in whole
or in part for human habitation, unless:
* * *
(c) For properties with an ADU, the property must also include the primary residence of the owner.
Sec. 13.503. OCCUPANCY LIMITATIONS
* * *
(4) Limits based on Zoning District – Maximum Occupancy
* * *
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(e) The maximum occupancy for a single-family or a two-family dwelling unit shall be based upon
compliance with all standards of the Code, including but not limited to parking spaces, area requirements, habitable
space requirements, and the following:
* * *
(iii) For properties with a single-family dwelling or duplex and an approved ADU, the maximum
occupancy of the single-family each dwelling unit is calculated based upon its individual bedroom count. , if it is the
licensed rental unit on a property. An ADU is limited to a maximum of three adults, if it is the licensed rental unit on
a property. In no event can both dwellings be licensed as rental units, regardless of owner residency.
* * *
CHAPTER 29, ZONING
* * *
Sec. 29.201 DEFINITIONS
* * *
(5)Accessory Dwelling Unit (ADU) means a detached “dwelling unit” on the same property with a single-
family dwelling that includes the Primary Residence of the owner an additional 1-bedroom residential dwelling unit,
attached or detached, located on the same lot as a single-family residence as defined by Iowa Code 562A.6.
(6) Accessory Structure means a subordinate structure detached from but located on the same lot as a principal
building. The use of an accessory structure must be incidental and accessory to the use of the principal building.
Accessory Structures include, but are not limited to, detached accessory dwelling units (ADUs), garages, sheds, and
fences.
* * *
Sec. 29.406. OFF-STREET PARKING
* * *
Table 29.406(2)
Minimum Off-Street Parking Requirements
PRINCIPAL LAND USE ALL ZONES EXCEPT DOWNTOWN
AND CAMPUS TOWN SERVICE
CENTER ZONES
DOWNTOWN AND CAMPUS
TOWN SERVICE CENTER ZONES
Residential Dwellings
* * *
Accessory Dwelling Units 1 space/RU Not Applicable
* * *
Sec. 29.408 OTHER GENERAL DEVELOPMENT STANDARDS
* * *
(7) Requirements for Private Garages and Other Accessory Buildings
(a) Accessory Dwelling Units are excluded from this section and must comply with Sec. 29.409.
(a) (b) The following requirements apply to private garages and accessory buildings in Agricultural,
Residential and Hospital/Medical districts:
* * *
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(b) (c) The following requirements apply to private garages and accessory buildings to legally nonconforming
Single Family and Two-Family Dwellings in Commercial and Industrial Districts:
* * *
(c) (d) When a special use permit is required for an institutional use, garages and accessory
buildings/structures shall be exempt from that requirement, if the accessory structure does not exceed 900 square feet.
Garages and accessory structures for an institutional use exceeding 900 square feet require approval of a special use
permit.
* * *
(d) (e) The following requirements apply to shared common lot line garages and accessory buildings in
Agricultural, Residential and Hospital/Medical districts:
* * *
Sec. 29.409. ACCESSORY DWELLING UNIT (ADU) STANDARDS.
An ADU is a specific type of accessory building with requirements additional to those of private garages and accessory
buildings provided in 29.408. An ADU is a newly constructed additional residential dwelling unit located on the same
lot as a single-family residence as defined by state law. This includes properties with a single-family or two-family
dwelling defined within the Zoning Ordinance.
(1)Where Permitted.
(a)An ADUs are is permitted in the following zoning districts: R-L, R-M, UCRM, FS- RL, FS-RM,
and F-PRD on any lot with only a single-family residence.
(i)One ADU is allowed on any lot having one existing single-family dwelling that is the
primary residence of the property owner, and no other dwellings are on the lot. If a lot has two or more dwellings, an
ADU is not permitted.
(b)Overlay zoning districts. If the property is in an overlay zone, such as the Single-Family
Conservation (O-SFC) or the Historic (O-H), it may be subject to additional design standards and permitting
requirements. In the event of conflict between overlay regulations and the regulations included herein, the more
restrictive regulations shall control.
(2)Independent Dwelling Unit.
(a)Detached from the principal building. Location. The detached ADU may be created through the
conversion of an existing detached structure or may be new construction creating a new standalone building. An ADU
may be:
(i)Attached to the single-family residence.
(ii)Detached from the single-family residence in a free-standing structure.
(iii)Located within a converted, existing accessory structure, so long as the structure complies
with all ADU requirements, including setbacks.
(iv)No ADU may be established as an addition to or within an existing single-family dwelling
residence.
(b)Functions Independently. The ADU must function independently from the single-family principal
residence. It must include its own bathroom and kitchen facilities and be connected to public utilities including water
and sanitary sewer. Separate metering is not required but allowed.
(c)Foundation. Whether constructed on site or premanufactured, an ADU must be placed upon a
permanent foundation.
(3)Lot Size Development Requirements
There is no minimum lot size for an ADU.
(a)All ADUs shall follow the same regulations as the single-family residence on the property
regarding:
(i)Maximum height
(ii)Minimum setbacks
(iii)Minimum lot size
(iv)Minimum building frontages
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(v)Maximum lot coverages
(vi)Density requirements
(vii)Aesthetic or architectural standards
(b)Where side setbacks are based on building height, the single-family residence and the ADU shall
individually have minimum setbacks based on their respective heights.
(c)ADUs are not regulated as accessory structures or accessory buildings in Sec. 29.408.
(d)ADUs are not subject to the rear yard coverage restrictions in Sec. 29.408.
(e)ADUs may be either freestanding or attached to the single-family residence.
(i)Attached ADUs must be of new construction and not a conversion of an existing dwelling.
(ii)Conversion of a detached accessory structure to an ADU must be in compliance with all zoning
standards, including setbacks and lot coverage as a newly constructed ADU. For example, a nonconforming detached
structure cannot be converted if it does not meet current zoning standards.
(f)The design of the ADU when attached to the home with a total of two doors facing the street is
subject to the design requirements of two-family homes.
(g)ADUs are not required to adhere to the minimum standards of 29.410(1)(a), relating to minimum
dimensions.
(4)Size Limitations and Bedrooms.
(a)The ADU may not exceed 1,000 square feet or 50% of the size of the single-family residence
whichever is larger.
(i)For purposes of this section, size of the single-family residence is calculated on the Gross Floor
Area as defined in Sec. 29.201.
(ii)For purposes of this section, the size of the ADU is calculated on the Gross Floor Area as
defined in Sec. 29.201.
(b)The ADU is subject to the gross floor area limitations of accessory buildings and is limited to one
bedroom. Any additional area or room that meets the definition of a bedroom as defined within the Zoning Ordinance
is prohibited.
(5)Parking & Driveways.
(a)One paved off-street parking space is required for the ADU in addition to the two spaces required
for the principal building. Although spaces for the principal building can include two cars parked in tandem, an ADU
parking space cannot be in front of or behind another required parking space. No on-site parking is required for the
ADU in addition to the required parking for the single-family residence. On-site single-family residence parking
must be provided to approve an ADU. If parking is provided, it All parking spaces must be paved and located in
accordance with the requirements of 29.406.
(b)Sidewalk. A sidewalk is required to connect the primary exterior entrance of the ADU with the
paved parking area, or to the single-family residence principal building, or the street.
(6)Occupancy.
(a)Owner-occupancy. No building permit or rental letter of compliance will be issued by the City for
an ADU unless the titleholder resides on the property as their primary residence. The property owner’s primary
residence may be either the principal building or the ADU. Prior to issuance of a permit, a “Notice of Limitation on
Rental” shall be recorded by the property owner, including an affidavit confirming their understanding of rental and
occupancy requirements. The “Notice of Limitation on Rental” shall be on a form prepared by the city. Properties
owned by an L.L.C. or other non-natural person entity do not qualify as owner-occupied.
(a)(b) The maximum occupancy of an ADU is limited to three adults. Additional Occupancy limitations
may apply to Near Campus Neighborhoods, as defined within Chapter 13, Rental Code.
(b)(c) Rentals. Only one of the two dwelling units on the lot may be a rental. Any ADU or single-
family residence principal building that is intended for use as a rental must be registered with the city and have a
valid rental permit. All requirements of Chapter 13, Rental Code apply.
* * * ”
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Section Two. All ordinances, or parts of ordinances in conflict herewith are hereby repealed to the extent of
such conflict, if any.
Section Three. This ordinance shall be in full force and effect from and after its passage and publication as
required by law.
Passed this day of , 2025.
_____________________________________________________________________________
John A. Haila, Mayor
First Reading:
Second Reading:
Third Reading:
Passed on:
I, Renee Hall, City Clerk of the City of Ames, Iowa, hereby certify that the above and foregoing is a true
copy of Ordinance No. _____________, passed by the City Council of said City at the meeting held on
____________________________, and signed by the Mayor on ____________________, and published in the Ames
Tribune on _________________.
__________________________________________
Renee Hall, City Clerk
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