There are as many reasons to build a second, smaller home near your house as there are styles in which to design the self-contained flat.

In Kol Peterson's new book, "Backdoor Revolution-The Definitive Guide to ADU Development" released Jan. 23, he outlines the differences between carving out space from underused rooms inside a residence, converting an unfinished basement or structurally sound garage into new living quarters with a kitchen sink, stove and shower, and adding a second story to a garage.

The most common compact home, or accessory dwelling unit (ADU) that shares a lot with a larger existing home, is a stand-alone, stick-framed structure on a foundation.

The most popular reason to build: People love their neighborhood or low mortgage, and don't want to move but they need more space or want to rent out an apartment for added income.

Some homeowners and the City of Portland say as long as the garage is falling apart and needs to be rebuilt, why not put an apartment on top? Read more at AcessoryDwellings.org.

Here are 10 reasons Portland homeowners decided to spend $73 to $353 a square foot to have a spare home nearby:

Everyone wants to make the most of what they have. Joan Grimm and Rita Haberman carved out space from an unused bedroom, small hallway and bathroom in their house in Southeast Portland's Richmond neighborhood to create a 220-square-foot studio with a full kitchen and bathroom plus living and sleeping areas.

They designed the compact dwelling and its separate entrance and Richard Wallace of R.S. Wallace Construction completed the build in 2015. The cost, including half of the work done by the owners, was $55,000 or $250 a square foot, says Grimm, an educator who co-founded PAD (Portland Alternative Dwellings), a resource center for tiny houses and smaller homes.

People building an ADU to downsize and simplify their lives move out of a big house they no longer want to pay to keep up. Smaller homes use less energy and materials in construction, and cost less to heat, cool and maintain.

In some cases, renting out the main house can cover the mortgage including the cost of refinancing to build a second home.

That was the case with Gina Ostby and Seth Gross, who built a 754-square-foot secondary home in the yard of their Southeast Portland property for $208,000 or $276 a square foot in 2017. Schuyler Smith of Polyphon Architecture & Design was the designer and Owen Gabbert was the builder.

Thomas Hudson had the same idea. He built a 528-square-foot detached dwelling as his primary residence in Northeast Portland's King neighborhood. It was designed by Ground Up Design Works to match the neighborhood and built in 2015 by Dan Maust Construction. The cost then was $98,000 including $15,000 of the owner's sweat equity ($186 cost per square foot).

Hudson's advice: "Talk to your neighbors so they feel comfortable and interested in your project."

Free ADU development talk

Kol Peterson, author of

($15 ebook, $25 print), is giving a free, public talk from 6 p.m.-7:30 p.m. on Saturday, Feb. 3, at 2120 NE Tillamook St. in Portland. Space is limited so registration is required at

3-Small budgets can pull off a basement conversion

Tatiana Xenelis-Mendoza served as the designer and general contracted for her 750-square-foot basement conversion completed in 2015 in her house in North Portland's Portsmouth neighborhood. She spent $55,000 on the project including $25,000 worth of her own time ($73 cost per square foot).

She used sustainable Oregon juniper in a window well that adds a more natural and softer look, and the ceiling was raised to meet code. She would have liked to have more natural light into the south west side of the apartment, but that part is under the porch and next to the chimney fireplace.

4-Get ready to age in place

Homeowners not only remodel their homes to age in place but a few transform garages into flat-surface dwellings for themselves or family members. Another way to have elderly parents close by but still allow everyone to lead semi separate lives is to build a second small home on the property tht's accessible to people with limited mobility.

Grant Sawyer had a 728-square-foot backyard cottage built to replace an old garage on his property in Southeast Portland's Richmond neighborhood. The new home, which was competed in 2014, was designed by Ray Culi of R&B Design Studio and built by Norm Yonemura of EcoPower NW.

The total cost of his high-performance home was $187,000, which includes $30,000 of the owner's work ($256 cost per square foot).

Inside the home is a wheelchair-friendly, durable concrete slab floor with a polyaspartic finish and space for a foldaway bed on the ground level as well as a roll-in shower and a toilet that is compliant with Americans with Disabilities Act (ADA) guidelines.

Outside, there is a raised-bed vegetable garden that reduces the need to lean over and allows someone to garden from a wheelchair.

Added benefit: After two years, Sawyer's spare home has produced excess energy and he's received an annual check that is helping pay back the upfront costs of the photovoltaic system.

Jim Forristal and Ada Kardos built a detached 374-square-foot flat on top of a new garage on their lot in Southeast Portland's Buckman neighborhood in 2015. At the time, they wanted the addition to be used as a short-term rental, space for visiting family and friends, and a party venue.

The structure, which has a cathedral ceiling, skylights and bay window, was designed by Dave Spitzer of DMS Architects and built by Forristal. The total cost was $130,000, including $40,000 of the owner's work ($174 cost per square foot).

Forristal's advice: "Think about the height of the finished structure, it's orientation to the sun's path and the effect of having a large massing in that location."

Constructive Form Architecture and Design conceived of a 500-square-foot addition to an existing garage conversion in Southeast Portland's Buckman neighborhood. The addition, built by Citilites Builders, was converted into an ADU in 2015.

The total construction cost in 2013 for this all-electric, energy-efficient home was $130,000, including $20,000 of the owner's time ($260 cost per square foot).

7-A place for a caregiver to live

Robert Mercer and Jim Heuer wanted a way to live in their house in Northeast Portland's Irvington neighborhood for the rest of their lives and generate income. They hired Dave Spitzer to design a 795-square-foot, self-contained apartment in the basement and Weitzer Co. to build it in 2016. The renovation cost $261,000 or $328 a square foot.

"An ADU offers the possibility of caregiver lodging in the future or even a place for us to live while we rent out the main house if we get to the point where we can't handle the stairs any longer," they said.

8-Short-term rental revenue



Susan Moray was one of the first to take a workshop from ADU expert Kol Peterson then convert her old garage off an alley in Southeast Portland's Ladd's Addition into an energy-efficient, self-contained tiny house. PDX Eco Cottage was completed in 2013 and she continues to rent it out for short stays.

In 2016, Moray invested in a second rentable home, PDX Urban Barn, that replaced a worn barn in her daughter's Southeast Portland backyard. "Besides income, as a recent retiree, I wanted to help increase the value and flexibility of this shared property," says Moray, who hired architect Jack Barnes to design and Matt Mansfield of Confluence Design Build to construct the 750-square-foot, free-standing structure that earned Earth Advantage Platinum status.

The cost was $265,000 or $353 a square foot, which included removing the old barn plus adding a fence and landscaping. Moray anticipates a return on her investment in six years.

Moray, who previously managed vacation rentals on Maui and Nicaragua, says people thinking of renting their second home need to be considerate of their neighbors, confirm it's legal and pay the added income and occupancy taxes.

9-Create work and community space

Mark Timby and Leighann Franson live in a 1926 bungalow in Northeast Portland and wanted more room to host family and visitors as well as office space since they are both self-employed. They hired Alan Armstrong to design and Shelter Solutions to build a 515-square-foot detached structure that can also serve as a community space for teaching small workshops and gathering friends. The cost in 2017 was $160,000 or $310 a square foot.

10-Portland wants more ADUs

When Brian Chodowski submitted permits to build a 400-square-foot garage to replace his detached carport in Northeast Portland in 2014, a staffer at Portland's Bureau of Planning and Sustainability suggested he create an ADU above the new garage.

Chodowski now has more living space to entertain and for guests to stay over, plus an Earth Advantage show home for his Cedar Designs/Linwood Homes dealership. The cost for the garage and ADU, which were completed in 2017, was $128,000 or $160 a square foot.

-- Janet Eastman



jeastman@oregonian.com

503-799-8739

@janeteastman



