How Much Does it Cost to Build an ADU?
January 1, 2023
The cost to build an ADU can vary widely depending on a number of factors, including the size and design of the ADU, the materials used, and the location of the property. According to a report by the National Association of Home Builders, the average cost to build an ADU in 2019 was $152,000, while a 2021 report by HomeAdvisor showed that the average cost to build an ADU in the United States was $72,214.
Other sources suggest that the cost to build an ADU can range from around $150 to $400 per square foot. This means that a 500-square-foot ADU could cost anywhere from $75,000 to $200,000 or more.
Here are some of the factors that can affect the cost of building an ADU:
Size: The larger the ADU, the more it will typically cost to build.
Materials: The cost of materials can vary depending on the quality and type of materials used. For example, high-end finishes such as granite countertops or hardwood flooring can increase the cost.
Location: The cost of labor and materials can vary depending on the location of the property. Building an ADU in an area with high labor costs or building restrictions, for example, may be more expensive.
Site preparation: If the site requires extensive excavation or grading, this can add to the overall cost. By the same token, if the site is an existing structure, such as a garage or an exisiting attached space, it may signficiantly reduce costs.
Permits and fees: Permit and impact fees can vary depending on the location of the property.
Existing utilities: If the ADU needs to be connected to existing utilities, such as water, sewer, and electricity, this can add to the overall cost.
According to Bankrate, which breaks down some of the different ADU types by cost, basement and garage conversions are the most cost effective, at $10k-$30k, while an attached addition will cost $40k-$125k, and a detached structure will $100k+. Adding a bathroom to any of these, if not existing, will set you back another $30k.
To reduce time and costs, it is worth looking at off-the-shelf, pre-approved plans that many municipal building departments provide, as well as prefab units from Adobu, Mighty Buildings, and the like, as these can be delivered to your home in a very short time frame, and often these companies will handle utility hookups, permitting, and provide financing in house.
It's worth noting that while building an ADU can be a significant investment, it can also provide long-term benefits such as rental income, increased property value, and additional living space for family members.
