The three main categories of cost for any ADU project are design, permits and construction. You can estimate the costs for your ADU project most accurately once you have a preliminary design for the project prepared. This is the most prudent first step that you can take in order to be well prepared to source cost estimates from contractors. Based on your design, experienced contractors will be able to give you an idea of the costs and timeline for your project with some level of accuracy.

We provide customizable ADU designs that are some of the most affordable in the industry. If you want to keep costs low, it helps to keep the floor plan fairly simple. ADUs that can use existing space have a huge advantage in keeping construction costs low, so it's important to choose the right design for you and your budget.

The Housable Solution: Our customizable ADU Design Report starts at $250 and up based on your design selections and project complexity.


It is typical for architecture firms to charge upwards of $10,000 for design and construction plans to permit an ADU project in California, excluding engineering fees and city permit fees. At Housable we have developed a process that allows you to get the customization and cost effectiveness that you need, without the high upfront design and engineering costs typically required to permit ADU projects.

The Housable Solution: Our standard ADU Permit Sets range from $2,900-5,800 including engineering fees.

Regardless of who builds your ADU or how it is built, city permit fees typically range from $2,500 to $10,000 in total, though these fees have been significantly reduced state wide in the past year. Here is a breakdown of what city fees typically cost depending on project size and scope.

  • Planning Review Fees - $500-1,000

  • Building Permit Fees - $1,500-3,000

  • Impact Fees - $1,500-3,500 (not applicable to ADUs under 750 sq. ft.)

  • School Fees - $1,000-2,500 (not applicable to ADUs under 500 sq. ft.)


Based on data from our projects in 2020, contractor estimates provided to our existing customers have ranged from $85,000 to $339,300 for their ADU projects over the past year. This range includes both garage conversion and new construction projects, ranging from 200 sq. ft. to over 1,000 sq. ft., located across The State of California and excludes all DIY projects.

The Housable Solution: Our ADU Marketplace now makes it easier than ever for you to source site visits and accurate cost estimates from local contractors who specialize in ADU construction.

Did this answer your question?