Start with daily life
Will the space be for a parent, an adult child, or another intended use? List the rooms, privacy, storage, and access needs before choosing finishes. A two-bedroom cottage and a one-bedroom garage conversion solve different problems.
Compare three building approaches
A detached ADU separates the new home from the main house. An attached addition connects new space to an existing building. A conversion reuses an existing footprint. Compare each approach with the property’s access, existing structure, utility locations, and desired layout.
Separate the building from the site budget
A published building budget is a starting point. Ask whether design, approvals, site preparation, utilities, drainage, and septic or sewer work are included. The planning ranges on our site are illustrations, not fixed offers; a written scope defines your actual price.
Confirm the path for your property
Start with your local building and planning departments and the professionals preparing your drawings. State ADU guidance is a useful reference, but it is not an approval for a particular lot. Review the property before committing to a layout or construction date.
Bring the right information
Send the property address, current photos, existing plans or a survey if available, intended use, approximate budget, and the features that matter most. We can discuss the next construction questions from there.
Helpful official resources
Reviewed October 2026. Confirm current requirements and project eligibility with the relevant offices. This guide offers planning questions, not property-specific approvals or construction pricing.