USA Site Plans
If you are planning an accessory dwelling unit (ADU) in Des Moines, Iowa, a clear site plan can make your permit application much easier to understand. Even a small backyard ADU affects the overall property layout. Reviewers may need to understand where the ADU will sit, how parking is handled, where utility connections may run, and how the new structure affects lot coverage and the use of the rear yard. [1][2]
Des Moines allows ADUs, but the city has specific rules about location, setbacks, and size. The city says no more than one ADU is allowed on a single lot, detached ADUs must be located in the rear yard, they must be set back at least five feet from any lot line, and the floor area of an ADU may not exceed 50% of the primary house or 1,000 square feet, whichever is larger. The city also says building an ADU requires permits from the Permit and Development Center before work begins. [1]
Why a Site Plan Matters for an ADU
A site plan is the drawing that helps show how the whole property works together. Des Moines defines a site plan as a document showing existing and proposed conditions, including the entire property drawn to scale, with the location and dimensions of property lines, existing and proposed structures, and exterior work. [2]
Des Moines also notes that residential projects with two or fewer units use a separate review process rather than the city’s formal site plan review process. Even so, homeowners still benefit from a clear permit drawing that shows the full property and the proposed ADU in a simple, readable way. [2]
What Should a Des Moines ADU Permit Site Plan Show?
A good ADU permit site plan should show more than just the new unit. It should explain how the proposed ADU fits with the existing home and the rest of the lot.
A strong Des Moines ADU site plan should include:
- Property lines and lot dimensions
- Existing house footprint
- Proposed ADU footprint
- Rear yard location of the ADU
- Setback dimensions
- Existing and proposed parking areas
- Driveway and walkways
- Utility connection routes, if known
- Patios or other paved areas
- North arrow and scale
When the site plan is clear, it is easier for the city to understand where the ADU is being placed and whether the layout appears to meet local requirements. [1][2]
Parking: What Homeowners Need to Know
Parking is one of the first questions many homeowners ask. Des Moines gives a helpful answer on its ADU page: city code requires a minimum of one off-street parking space for the primary house, but additional parking for the ADU is not required. [3]
That means your ADU site plan should still show the existing off-street parking for the main house. Even though a second parking space for the ADU is not automatically required, reviewers still need to see how the lot is arranged and where the existing parking sits.
If the property already has a driveway, parking pad, or garage, show it clearly. If the ADU project changes any paving or parking layout, show that too. A clear parking note can help prevent confusion during permit review.
Utilities: Water, Sewer, Electric, and Other Services
Utilities are another important part of an ADU permit site plan. The City of Des Moines explains that if your ADU plans require additional utility hookups for water, sewage, or electricity, those costs must be considered before applying. The city specifically says homeowners should check with utility providers to determine what will be required to serve the ADU. [1]
The city also explains that whether an additional sewer line ties into the existing house or is separate depends on the location, depth, and capacity of the existing utilities compared with the location of the proposed ADU. [3]
For that reason, your site plan should show utility information whenever possible. It can be as simple as identifying the approximate route of water, sewer, gas, or electric service from the main house toward the proposed ADU. If exact utility routing is not yet known, the plan can include a note that utility connections will be verified before construction.
Lot Coverage: Why It Matters
Lot coverage matters because an ADU adds another structure to the property. Des Moines notes that all accessory structures with roofs contribute to maximum building coverage, and other accessory structures or impervious paving contribute to the maximum impervious area for the site. [4]
For many residential lots in Neighborhood (N) and Neighborhood Mix (NM) districts, Des Moines also states that the lot coverage of all accessory structures shall not exceed 576 square feet or 25% of the rear yard. [4]
This is one reason a permit site plan should show the existing house, the proposed ADU, and nearby paved areas all together. Even if your detached ADU meets setback rules, the city may still need to understand how much of the rear yard is being occupied by structures and hardscape.
Location in the Rear Yard
Des Moines specifically says detached ADU buildings must be located in the rear yard. [1] Your site plan should make that obvious. The drawing should show the main house first, then the proposed ADU behind it in the rear portion of the lot.
This is especially important on narrower or shallower lots where the ADU placement could be questioned. A clear site plan can show that the new unit is in the correct part of the lot and that it still leaves the required spacing to property lines.
Setbacks and Size
The city says ADU buildings must be set back at least five feet from any lot line. It also says the height cannot exceed the maximum permitted for the primary house and that permitted roof types are limited to those allowed for the main house. [1]
On the site plan, show the setback dimensions clearly. Label the distance from the ADU to the rear lot line and each side lot line. If there is a fence, driveway, patio, or other feature nearby, keep that visible too so the whole layout is easy to understand.
It is also smart to note the ADU footprint on the plan. That helps connect the site layout to the city’s maximum size rules.
Common ADU Site Plan Mistakes
Homeowners often run into delays when the permit drawing leaves out practical information. Common problems include:
- Not showing the existing off-street parking space
- Leaving out utility notes or utility routes
- Not showing property lines clearly
- Forgetting to label setbacks
- Showing only the ADU and not the whole lot
- Leaving out patios, paved areas, or other impervious surfaces
- Not showing that the detached ADU is in the rear yard
- Using a rough sketch that is not to scale
A clean and complete permit site plan helps reduce these issues and makes the review process smoother.
What Homeowners Should Gather Before Ordering an ADU Site Plan
Before ordering a Des Moines ADU permit site plan, it helps to gather:
- Property address
- Approximate ADU size
- Survey or plat, if available
- Photos of the backyard and driveway
- Location of the existing house and garage
- Known utility information
- Parking layout
- Any planned patio, walkway, or paved area near the ADU
The more information you have at the start, the easier it is to create a site plan that clearly shows parking, utilities, and lot coverage.
Need a Des Moines ADU Permit Site Plan?
USA Site Plans prepares clear, easy-to-read permit site plans for homeowners across the United States. If you are planning an ADU in Des Moines, we can help show the proposed unit, parking, utility connections, setbacks, property lines, and lot layout in one clean drawing.
A well-prepared site plan can make your permit submission easier to review and help reduce comments about missing parking information, unclear utility routing, or rear-yard lot coverage.
Order your Des Moines ADU permit site plan today and get a clear drawing for your permit submission.