New laws across the Western U.S. are making it easier and cheaper add Accessory Dwelling Units, or ADUs, to single-family homes.

Also known as granny flats, mother-in-law units or backyard cottages, ADUs are typically around 500 to 700 square feet with a bathroom and kitchen. ADU residences can be build-ons, re-purposed space or a separate, free-standing unit.

In the housing market, homes with ADU potential are increasingly attractive to many buyers of more modest income who might rent out part of the home to help make ends meet.

Homeowners most burdened by housing costs include seniors, low-income families, and households of color.

ADUs are also attractive to families with older relatives on fixed incomes, or older homeowners looking to downsize and rent out their main property. Estimates for the cost of constructing the units vary from builder to builder and city to city.

In cities like Los Angeles, Seattle, Portland, OR, Boulder, CO, and Bellingham, WA, permits to build ADUs have exploded after local legislators eased restrictions.

In the states of California and Washington, bills are gaining traction that would waive most development fees on ADUs statewide. Lawmakers see ADU reform as the kind of low-hanging fruit that could ease affordable housing shortages.

As of January 1, 2019, a new California law allows homeowners who built ADUs without permits an opportunity to bring their ADUs into compliance.

Local building officials now have the option to inspect the ADU and apply the building standards that were in effect at the time the unit was constructed.

The most effective way to solve the nation’s housing crunch might not be building more single-family homes, but by building new homes with Accessory Dwelling Units, or adding ADUs to existing property.

Homeowners will want to consider the future impact of an ADU on future resale value. Some buyers shy away from “overbuilt” properties, and an ADU not built to code could be a problem.