As household formation and new home starts lag, researchers at the National Association of Home Builders wondered if more people were doubling up in existing housing. In other words, were more Accessory Dwelling Units (ADUs) being built?
There are no existing data sources as local ordinances requiring permits vary across the country and there is no federal standard or program to collect information in a consistent way. So NAHB attempted to detect this trend by asking in its Remodeling Market Index survey for first quarter 2019 if remodelers were involved in projects during the past 12 months to create more living space whether it was an addition, a refinished second floor, a finished basement with a kitchen, or a space with a separate entrance.
The results showed that one-fifth of remodelers that created an ADU took on projects that did so by converting an existing space and 18% did so by building an addition. Only 6% reported completing ADUs that cost less than $25,000.