ADU Cost & Home Value Estimator.
Real data, zero guesswork.
Estimate your complete turnkey build investment, immediate home equity addition, and construction timeline across Orange County.
Every ADU Alliance contract includes 3D architectural plans, structural engineering calculations, 100% city permit management, site excavation, concrete foundation, structural framing, 200A electrical subpanel, plumbing, HVAC, and turnkey interior finishes.
How ADUs Impact Property Taxes & Grants
California Prop 13 Protection
Adding an ADU does NOT trigger a reassessment of your primary house. Only the newly constructed square footage is assessed at current value, typically adding only $900 - $1,600/year to your total tax bill.
CalHFA $40,000 ADU Grant
California Housing Finance Agency provides up to $40,000 in non-repayable grants toward pre-development costs (permits, architectural design, engineering) for qualifying homeowners.