Thinking Big by Building Small

June 10, 2021 | By: Allie Callow-Spencer

ADU photo
Thinking Big by Building Small

For almost 75 years, the size of a typical US home increased while the number of occupants decreased. Homes in the 1950s were about 1000sf and averaged almost 4 occupants. By 2015, a median US home was 2,467sf with fewer than 3 occupants. As the demand for housing continues to increase and housing affordability reaches crisis levels in many parts the country, this historic trend seems to be waning; in 2020 home size fell to 2,333 square feet. Many states across the nation are looking for ways to encourage smaller, more cost-accessible housing types that can help address prevailing land cost and affordability issues. 

Photo of an accessory dwelling unitAccessory Dwelling Units (ADUs) are one of the key housing solutions that many state and local governments have enabled. We are witnessing exponential growth of the ADU industry in several key markets that have created greater regulatory flexibility (California, Oregon, Washington, and Hawaii) or in jurisdictions with fewer zoning regulations to begin with (Texas and Florida). Recent analyses have shown ADU growth of 15%-22% in markets like Portland, Dalles, Seattle, Los Angeles, Miami, and Austin. 

To meet this growing market need, Earth Advantage is focusing on helping to create a legion of qualified professionals to help build, sell, and appraise those ADUs. The ADU Specialist Accreditation helps set knowledge standards for this new industry, while allowing these professionals to differentiate themselves in an increasingly crowded (and sometimes confusing) marketplace. ADUs can be a little quirky, with different, sometimes hyper-localized issues related to permitting, designing, building, and selling. Earth Advantage has partnered with industry experts across Oregon, California, Colorado, Hawaii, and Washington states to help local professionals understand key ADU concepts related to site eligibility, regulatory restrictions, development processes and costs, and design considerations like zero energy construction. ADU Specialist Logo
With a changing regulatory environment, it’s not always easy to keep up with the latest information related to ADU construction. To meet this need, Earth Advantage will be offering some upcoming courses: 

A recorded ADU site visit will soon be available as an on-line, on-demand course. Josh Salinger, founder of Birdsmouth Design/Build, will walk you through various stages of construction of a “Zero Energy Ready” ADU. These ADUs will demonstrate construction approaches and systems that significantly reduce power dependency. This site visit is just one of Earth Advantage’s features within the Sustainable Homes Professional program. 

Did you know?

  • Seattle adjusted the lot size requirement, removed the owner-occupancy requirement, and removed the off-street parking requirement per unit for ADUs.
  • Portland allows up to two ADUs on a typical single family lot.
  • Los Angeles accepted Movable Tiny Houses (MTH) as a viable residential structure.
  • San Diego created a density bonus of 1 ADU for every deed-restricted affordable ADU provided.

Get recognized!

There are over now 300 recognized ADU experts nationwide who have achieved Earth Advantage’s ADU Specialist Accreditation. Completion of this program includes a listing on Earth Advantage’s National Registry and logo materials to include in marketing collateral. 

For more information on ADU trainings or the ADU Specialist Accreditation, contact:

Allie Callow-Spencer, Training Development Lead 

photos on this post courtesy of