There is no universal ADU application package. The documents and inspections depend on the property, unit type, scope of work, code path, and authorities involved. Treat any generic checklist as a preparation aid; the responsible authority’s current project-specific requirements control.

Build a package around the application

Ask the planning or zoning office and building department for the current forms and drawing standards before commissioning a complete set. Depending on the route, a package may call for:

  • an application form, owner authorization, property or parcel details, and a clear description of the proposed use;
  • a site plan showing the existing buildings, proposed unit, access, boundaries, and relevant site features;
  • floor plans, elevations, sections, dimensions, and construction details;
  • surveys, structural calculations, energy information, or other professional documents where the authority requires them;
  • utility, drainage, fire-access, environmental, heritage, or other agency confirmations that apply to the site;
  • project-specific declarations or supporting forms, such as an existing-building or hazardous-material form when required.

These are possible document types, not a representation that every authority asks for all of them. Calgary’s local secondary-suite guide, for example, lists site plans, floor plans, elevations, and additional forms for some applications. Ontario’s homeowner guidance describes an application, construction drawings, supporting documents, and a permit fee, while directing applicants to speak with the municipal planning and building departments. Neither checklist substitutes for the local authority’s current instructions.

Keep parallel permits and inspections visible

Map each approval to the office that issues it. Planning or zoning permission and building approval are distinct. Electrical, plumbing, gas, mechanical, fire, utility, drainage, and environmental work may require separate permits, inspections, or confirmations. A factory-built component can also have a separate certification or site-installation path. Confirm the order: some authorities require a planning decision before a building application, while trade permits or utility checks may proceed separately.

After work begins, follow the inspection schedule in the issued permits. Contact the relevant department when a required stage is ready, keep inspection results and correction notices, and resolve outstanding items before covering work or moving to the next stage where the authority requires it. Seattle and Calgary describe local permit and inspection processes; those examples do not establish the sequence in another jurisdiction. For city-specific steps, see the NYC DOB NOW filing guide, Calgary secondary-suite guide, and Portland ADU permit guide.

Close out the project and preserve the record

Before treating the project as complete, ask each authority what final evidence it issues or requires. Depending on the jurisdiction and permit, this may include passed inspection records, a completion or occupancy certificate, a final permit status, a registration record, or updated property records. Building approval or a final inspection does not by itself settle zoning, private restrictions, utility capacity, or every separate approval.

Keep a copy of the approved plans, permit numbers and conditions, inspection results, change approvals, final certificates, and authority correspondence with the property records. If the design changes during construction, confirm whether revised drawings or an amendment must be approved before proceeding.

Existing units follow a different route

Do not use a new-work checklist to assume an existing or unpermitted unit is legal. Some authorities offer a retrospective or regularisation process, which may require opening up work, alterations, additional inspections, or a different application. England’s building-regulations guidance, for example, describes local-authority regularisation for certain completed work; Calgary separately identifies pre-2018 and existing-suite processes. These are jurisdiction-specific examples. For a unit already built, start with the records and legalization questions for that authority before assuming the normal new-project sequence applies.