How Much Does It Cost to Build an ADU in 2025?

<h2>ADU Construction Cost Breakdown</h2><p>Building an Accessory Dwelling Unit is a significant investment, but understanding the costs involved can help you plan effectively and avoid surprises. Here is a comprehensive breakdown of what to expect.</p><h3>Average Costs by Type</h3><p>The cost of building an ADU varies widely depending on the type, location, and finishes you choose:</p><ul><li><strong>Garage Conversion:</strong> $50,000 - $150,000</li><li><strong>Basement Conversion:</strong> $60,000 - $180,000</li><li><strong>Detached New Build:</strong> $150,000 - $350,000</li><li><strong>Prefab/Modular:</strong> $100,000 - $250,000</li></ul><h3>Cost Factors</h3><p>Several factors influence the final cost of your ADU project:</p><ul><li>Location and local labor costs</li><li>Size and complexity of the design</li><li>Foundation requirements</li><li>Utility connections</li><li>Permitting and impact fees</li><li>Interior finishes and appliances</li></ul><h3>Tips for Staying on Budget</h3><p>Work with an experienced ADU contractor who can provide accurate estimates, consider phased construction if budget is tight, and always include a 10-15% contingency fund for unexpected costs.</p>