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Valley Home Builders

House remodeling,design and build

How Much Does An ADU Cost?

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Many factors determine the overall ADU cost. Use our ADU estimator tool below to get an approximate estimate of the cost of a new accessory dwelling unit. Choose the features you want, the quality level of finishes and the type of unit you are looking for.

Valley Home Builders is your solution to building an ADU in Santa Clara and the South Bay Area of California. Whether you live in San Jose, San Mateo or anywhere in the South Bay, Valley Home Builders can help you build or convert an accessory dwelling unit. Each project is different, and we customize our services in addition to focusing on customer satisfaction and increasing property value.

Use Our Estimator Tool and Contact Valley Home Builders to Get Started

This estimator tool should only be used to get a rough estimate of costs and is not an official quote for our services. To get an official quote on your ADU building project and set up a free consultation with a member of our team, fill out our contact form and we will reach out to you shortly!

Benefits and Costs of ADU Types

ADU costs in California are usually over $125,000 and can go up to $300,000 or more, including materials and labor. Reliable ADU builders like the Valley Home Builders team can help you decide which of the following ADUs best suits your property and needs:

  • Detached: Separate ADUs incur more utility costs and extensive site work, but they offer the benefit of increased privacy and freedom to build without relying on existing structures.
  • Attached: Attached accessory dwelling units are more cost-effective overall since they utilize the available structures and utilities. An attached ADU can be accessed from the main home — ideal for guests or in-laws who want to stay close but still enjoy privacy.
  • Garage conversion: Projects like garage conversions are typically the most affordable since the existing walls, roof and electrical connections are already in place.

Cost Considerations and Breakdown

While there are many factors that go into the cost of an ADU, ultimately they all add value to your property and provide you with additional living space. Here are some of the components that make up the final ADU cost, which varies depending on your property, location and requirements:

  • Impact Fees: In some cases, these fees are not required for ADUs under 750 square feet.
  • Size: The planned accessory dwelling unit size will affect the cost, so consider the proportions of your ADU floor plan. The average cost of a complete ADU is between $350 and $800 per square foot.
  • Condition of existing structures: The final building cost will be affected by the use of existing structures and the amount of improvement and additional work required.
  • Permits: Depending on local regulations, permit costs may be required. At Valley Home Builders, we will help you organize the necessary building permits and ensure compliance.
  • Funding: There are funding options available for ADUs in California.
  • Site preparation: The cost of site preparation will depend on the existing condition of the proposed site and what is required beforehand.
  • Utilities: Utility costs will vary depending on whether your accessory dwelling unit is detached as well as the requirements for new connections.
  • Architecture and design: The design, planning and architecture stages are done in-house at Valley Home Builders for your convenience.
  • Boundary survey: If you are unsure of your property lines, a survey will ensure the building is not constructed too close to any boundary.
  • Construction costs: The materials and labor will account for the largest part of the final ADU cost.
  • Additional features: Adding a deck or other structural feature to an accessory dwelling unit will cost more but increase your property’s value.