Getting an ADU approved can sound pretty simple until you actually start dealing with drawings, codes, setbacks, and all the little details a permit reviewer wants to see. Good Accessory Dwelling Unit plans are more than a sketch showing where the bedroom and kitchen will go. They need to explain the project clearly enough that the city, contractor, and tradespeople are all looking at basically the same thing. Miss something important and the plans can get kicked back. Then you’re waiting, revising, sending them in again. Not exactly fun. Knowing what normally goes into a complete plan set can save a lot of back-and-forth later.
Start With a Clear Site Plan
The site plan is one of the first things reviewers will look at because it shows how the ADU fits on the actual property. It usually identifies the existing house, proposed ADU, property lines, driveways, walkways, utilities, and other structures on the lot. Setbacks matter here too. The drawings should make it obvious how far the new building sits from property boundaries and nearby structures. Depending on the local jurisdiction, there can also be requirements involving parking, easements, trees, drainage, or access. A rough placement idea isn’t enough. The reviewer needs dimensions and enough site information to understand what you’re proposing.
Floor Plans Need More Than Room Names
The floor plan is where the ADU starts becoming a real building instead of an idea on paper. It should show room layouts, dimensions, doors, windows, stairs if there are any, fixtures, cabinets, appliances, and other important components. Wall types and construction information may also need to be identified. A good plan makes the flow of the space easy to understand without making someone guess what a line means. This is especially important with smaller units, because every few inches can affect how the kitchen, bathroom, storage, and living areas work together. If the layout doesn’t make sense on paper, it’ll probably be frustrating once the walls are actually there.
Exterior Elevations Show What Gets Built
Floor plans tell you what’s happening from above. Elevations show what the ADU will look like from the outside. These drawings typically include each relevant exterior side of the building, along with wall heights, rooflines, windows, doors, exterior finishes, and other visible features. Height restrictions can be a major permitting issue, so the elevations need to make that information clear. If the ADU has a different roof design, siding, trim, or other architectural details, those should be documented too. Cities aren’t only checking whether the building fits on the lot. They may also be checking how it relates to the surrounding property and applicable design standards.
Building Sections Explain the Construction
A section drawing basically cuts through the building so the reviewer can see how the pieces come together. It can show floor assemblies, wall construction, ceiling heights, roof structure, insulation, foundations, and other details that aren’t obvious from a normal floor plan. This is where the technical side of the project starts showing up in a serious way. Depending on the project and local requirements, structural details may need to be included or provided on separate structural sheets. The point is pretty straightforward: the plan set has to show not just what the building looks like, but how it’s intended to be constructed.
Structural Drawings Can’t Be an Afterthought
For many ADU projects, structural information is a major part of the permit package. Foundation plans, framing details, roof framing, beams, headers, connections, and other structural elements may need to be documented based on the design. The exact requirements depend on the building, local code, and jurisdiction. An ADU attached to an existing home can also bring up different structural questions than a detached unit. This is one area where guessing is a bad idea. If an engineer is required, their work needs to coordinate with the architectural drawings rather than being treated like a separate puzzle that gets solved at the end.
Electrical, Plumbing, and Mechanical Details
An ADU is a small home, but it still needs the basic systems that make a home work. Electrical plans can identify outlets, switches, lighting, panels, and other electrical components. Plumbing drawings can cover supply lines, drains, fixtures, water heaters, and related connections. Mechanical information may show heating, cooling, ventilation, and equipment locations. Energy requirements can also affect windows, insulation, HVAC equipment, lighting, and other parts of the design. These details aren’t just there to make the plan set look complete. Contractors need them to build from, and permit reviewers need enough information to determine whether the proposed systems meet applicable requirements.
Energy and Code Information Matter Too
Building codes don’t stop at the walls and roof. An ADU plan set may need code notes, energy documentation, accessibility information where applicable, fire-related details, and other compliance information required by the local authority. Things like smoke and carbon monoxide alarms, emergency escape openings, insulation values, window requirements, and ventilation can all become part of the review. The exact checklist varies by location, which is why copying an old plan set from another project isn’t always smart. A drawing package that worked in one city may not satisfy another jurisdiction. Local requirements should drive the final documents.
Where Small House Plans Fit In
People sometimes look at small house floor plans when planning an ADU because the spaces have some obvious similarities. Both need to squeeze useful living areas into a limited footprint, and both benefit from smart circulation and practical storage. But an ADU still has its own zoning, building, utility, and site requirements. You can’t simply grab a tiny home layout, put it on a lot, and assume it’s permit-ready. The plan has to be adjusted for the actual property and local rules. That might mean changing windows, shifting walls, modifying setbacks, dealing with utility connections, or reworking the foundation. Small doesn’t mean simple.
A Complete Plan Set Makes Permitting Easier
There is no magic shortcut around permitting, but a well-coordinated drawing set can make the process a lot less painful. Before submitting, the architectural sheets, structural documents, energy information, and building systems should all agree with each other. Dimensions shouldn’t conflict. Door and window locations should line up. Structural elements shouldn’t mysteriously appear where a plumbing line needs to run. Sounds obvious, but these little mismatches happen more often than people think. A complete ADU plan set gives the reviewer enough information to understand the project without chasing missing details. That’s really the goal. Clear drawings, accurate information, and fewer reasons for the permit office to send the package back.
Conclusion: Plan for the Review, Not Just the Build
An ADU plan set isn’t simply a collection of drawings that make the new space look nice. It’s a technical record of what you’re asking the city to approve and what the builder is expected to construct. Site plans, floor plans, elevations, sections, structural information, and building-system details all have a job to do. Requirements will vary depending on where the property is located, so checking local rules early is worth the effort. It may feel like extra paperwork at first. In reality, getting the details sorted before construction starts can prevent much bigger headaches once the project is underway.