Side-By-Side Comparison
| Factor | ADU | Garage Conversion |
|---|---|---|
| Cost basis | New foundation, envelope, utilities, access, documents, permits, and finishes | Existing slab, framing, utilities, parking, waterproofing, and code upgrades |
| Schedule basis | Property feasibility, professional documents, jurisdiction review, utilities, inspections, and construction | Existing-shell condition, required documents, parking/code compliance, utilities, inspections, and construction |
| Best for | Rental income, family suite, long-term property value | Faster extra living space, office, studio, or smaller rental plan |
| Main risk | Utility upgrades, setbacks, plan review, site constraints | Parking replacement, ceiling heights, waterproofing, existing slab condition |
Contractor Recommendation
If the garage structure is sound and the property can satisfy parking and code requirements, a garage conversion is usually the faster value play. If the goal is maximum rental income, privacy, or long-term resale impact, a detached ADU is often the stronger investment even though the upfront cost is higher.
Do not choose from averages alone. Start with the property constraints: access, utility route, setbacks, parking, drainage, and whether the existing garage shell is worth saving.