PRE-APPROVED CASITA
MODEL PLANS
WORKSHOP
March 1 4 , 2 0 2 4
AGENDA
• Casita Model Plan Library Overview
• Using the TDC System
• Requirements for a model plan submission: Construction Documents
• Review each area
• Address questions we’ve heard
• Time for additional questions
• Submitting to the Casita Model Plan Library
Fees for Homeowners
• Licensing: designer determined; not collected by the City
• Administrative fee: $55 to use model plan and includes
first review of the plot plan
• Permit fee
• Impact Fees
• Possible site-specific fees
Intellectual Property
• Contracts for plans are between
designer and homeowner
• Need an authorization for use
• Additional protections of
intellectual property
Using the TDC System
Design Options
For designs with options such as studio one bedroom
• Suggested each option to be submitted separately
• Can keep costs down
• Streamline plot plan review
• Additional drawings can be submitted for additional
review fees beyond the $55 administrative fee
• Two exterior elevations options are acceptable; layout
cannot change
Requirements for a Casita
Model Submission:
Construction Documents
Full Construction Documents
• 2018 International Residential Code (IRC), local amendments, and City of
Tucson adopted design ordinances
• Casita plans are not required to be prepared by a registered design
professional unless there are any structural members that exceed twenty
feet (20) in length.
Submission Format
• All documents shall be in PDF format, with a graphic scale, and rotated so pages
read upright.
• Verify you have unlocked and flattened all the drawings and reports.
• Sheet title block sizes and locations shall remain constant on each page of the plan
set.
• Reserve the same location, minimum size of 3”x 5”, on all plan sheets for City
stamps.
• Files should only be saved in black and white. Light colors may be difficult to see
after the file is switched to grey scale.
• Documents, drawings, and reports must be submitted as a separate PDF for each
document type, i.e. plans, calculations, specifications, application, etc.
Model Plans must include the following drawings:
• Floor Plan
• Foundation Plan
• Roof Plan
• Exterior Elevations
• Building and Wall Sections
Common Architectural Questions:
What building and development codes do model casitas need to abide by?
• All new residential buildings in Tucson need to be in alignment with the 2018
International Residential Code (IRC), local amendments, and City of Tucson adopted
design ordinances (PDSD building codes site).
• The Inclusive Home Design Ordinance is a visitability code that provides guidance for
all newly built dwellings in the City of Tucson for minimum accessibility criteria such as
lever-type door hardware and zero-step building entry.
• The installation of solar panels is not required but must be prepared for in the future if
not included. Reserving roof space and electrical service capacity for future panel
instillation. Review the solar readiness ordinance for specifics on how to meet the solar
readiness requirements. For model plan design purposes, the electrical should be
designed as if the casita has its own electrical service. This will facilitate the plan review
process and can be revised when a site plan is submitted to reflect using the existing
electrical service of the primary residence as necessary.
Common Architectural Questions:
Is a separate drawing that shows an egress plan required/does the egress plan need to be
annotated in a particular way?
• A separate egress plan is not required for ADU plans. However, every casita must
include at least one exterior swinging door 36” wide and include emergency escape and
rescue openings are required for all sleeping rooms.
Are structural calculations required to be sealed by the registered design professional for a
casita model plan?
• An engineer is required if the casita design includes:
• A beam of more than 20 ft
• Any free-standing walls greater than 7ft in height
• Retaining walls retaining 3ft of earth or more
Common Architectural Questions:
Can a design using prefabricated building materials be a casita
model plan?
• Yes. These designs are reviewed and approved by the State of
Arizona. Designs that have received an Arizona certification for a
modular building can be included in the Casita Model Plan Library.
Any architectural questions?
Mechanical, Electrical,
Plumbing
What Needs to be Included: Electrical
• Electrical Plans
• One Line or Riser Diagram
• Panel Schedule
• Lighting and Outdoor Lighting Code
Common Electrical Questions
Do casita model plans need to show assigned circuit numbers and panel names/numbers
for each outlet?
• Yes, a complete panel schedule, circuit designation, and riser diagram are required
Is a One Line Diagram necessary for a casita model plan application?
• A One Line Diagram or a riser diagram may be used.
Do casita model plans need to demonstrate compliance with Lighting and Outdoor
Lighting Code?
• Yes, all exterior lighting must conform with the Outdoor Lighting Code (OLC). Model
plans will not include a lighting calculation but must include the fixture type, location,
lumens, and color temperature (Kelvin). The 2012 OLC is the currently adopted lighting
code at this time. Please be advised that this code is currently undergoing revisions.
Common Electrical Questions
Do model plans need to include a complete set of heating/cooling load
calculations? Do those calculations need to be sealed by the registered design
professional?
• New residential dwellings are required to include heating and cooling. The
mechanical load calculations used to properly size the system must be included
in the initial submittal, but they do not need to be completed by a licensed
professional. REScheck from the Department of Energy can be used to
complete the energy calculations and other proprietary software may be used
for the mechanical system design.
How do models demonstrate the electrical element of solar readiness?
• Note the electrical capability in the electrical plan and space on the panel.
Any electrical questions?
What needs to be included: Plumbing
• Plumbing Plans
• Plumbing Fixture Schedule
• Gas Piping Plan and Gas Demand Calculation (if using
natural gas)
Common Plumbing Questions
What information for water needs to be included on a casita model
plan?
• A model plan must include plumbing fixture unit schedule and
water supply calculation to establish the minimum diameter of the
water supply piping from the water meter. When a site plan is
submitted, the size of the water meter and total developed length
of water supply piping must be shown. For casitas that share a
water meter with its primary dwelling, all the fixtures in both
buildings must be included in the water supply calculations and
demand schedule.
Any plumbing questions?
What needs to be included: Mechanical
• Mechanical Floor Plans
• Equipment Schedules
• Ventilation Calculations
• Provide calculations acc ording to 2018 IRC
What needs to be included: Structural
• Foundation Plans
• Structural General Notes
• Lateral Bracing
• Floor & Roof Framing Plans
• Structural Details
• Deferred Submittals such as pre-engineered roof trusses
Any additional questions for the building team?
Model Plan Review
• Casita Design Competition Selected Designs: review
fees covered
• All are welcome to submit: review fees based on
valuation
• Plans approved in other jurisdictions: IGA and flat fee of
$300
Maintaining Model Plan Status
• Model plans are valid for one year and may be renewed
until the applicable codes are updated. After a new
building code is adopted, model plans may not be
renewed but will remain valid until their established
expiration date
Requirements for a Casita
Model Plan Library
Submission
What’s needed for the website
• Name of Firm w/ contact info (email, website, phone, etc.)
• Name of Casita / Design
• Cost to license the design
• Size in square footage
• Number of Bedrooms
• Number of Bathrooms
• Short Description (300 characters or 50 words)
• Long Description (1000 characters)
• Up to 8 images with cover image noted
• Model Plan Permit Number for Internal Reference
THANK YOU
For your contributions to
supporting additional
housing in Tucson
