Accessory Dwellings

A one-stop source about accessory dwelling units, multigenerational homes, laneway houses, ADUs, granny flats, in-law units…

Roger & Martha’s tiny house — economical, artistic, and prefab

Prefab dwellings seem like a great way to create ADUs — but they’re not as common as you might think. One Portland resident shows how it can work.

May 20, 2020 · 4 Comments

Accessory dwelling units and the coronavirus: can ADUs help?

The author is quarantined in his own accessory dwelling unit, during the coronavirus pandemic.

March 20, 2020 · 1 Comment

ADU classes for Portland homeowners- postponed due to Coronavirus- Special offer for Portland Metro locals

Kol Peterson, one of the editors here, hosts a class called “Building An Accessory Dwelling Unit on your property,” on Please visit Kol’s site for more details.

December 10, 2019 · 2 Comments

I’m semi-retiring! (On a personal note…)

I’m semi-retiring as a co-editor and numbers guy at accessorydwellings.org . But the site is alive and well.

October 24, 2016

Will short term rentals actually reduce long term housing in granny flats?

It’s not intuitive, but prohibiting short-term rentals in ADUs won’t necessarily lead to a bigger supply of long-term residential housing. This post includes new data about the number of ADUs and short-term rentals in Portland, and the longevity of short-term rental listings.

April 4, 2016 · 5 Comments

Real estate rage in Portland! Or, ode on a purple shed

Up for rent in Portland, February 2015: a tiny purple structure in someone’s backyard, apparently a converted garden shed. At 165 square feet, it had the same area of 5 … Continue reading

May 27, 2015 · 10 Comments

Summing up ADU research: are accessory dwelling units as great, or as horrible, as people say?

Collected research about accessory dwelling units (AKA granny flats, laneway houses, in-law units, etc) suggests they have many potential benefits, and two common arguments “against” are unsupported.

September 17, 2014 · 15 Comments

Accessory dwelling units: what further research should be done?

ADUs are especially promising as environmentally sensitive and affordable housing, and this potential should be investigated in detail.

September 3, 2014 · 4 Comments

What are the barriers to ADU development?

Government rules strongly limit the development of ADUs, but they are not the only factor.

August 21, 2014 · 10 Comments

Do ADUs provide affordable housing?

If the “grassroots” nature of their development is properly understood, ADUs have a lot of potential to address affordable housing needs.

August 7, 2014 · 17 Comments

How do ADUs contribute to the local economy? (Or, will building an ADU raise my property taxes?)

Will building an ADU raise your property taxes? Very likely yes. Is that a good thing for the community?

July 30, 2014 · 6 Comments

Do accessory dwelling units serve older persons? (Or, who lives in, and owns, ADUs?)

Older persons are expected to benefit from ADUs. Is this happening now, and will it happen more in the future?

July 23, 2014 · 3 Comments

Do ADUs cause neighborhood parking problems?

The single biggest and most specific fear mentioned by ADU opponents is loss of street parking. Is there any evidence on this?

July 16, 2014 · 7 Comments

Are ADUs green housing?

New evidence shows that ADUs have serious potential as environmentally sensitive housing.

July 9, 2014 · 7 Comments

How do ADUs affect property values?

Opponents of ADUs frequently charge they will bring down property values for the whole neighborhood. What is the evidence?

July 2, 2014 · 10 Comments

How much do ADUs cost to build?

Some survey results about ADU costs… and some thoughts about why ADU developers aren’t usually real estate “pros.”

June 25, 2014 · 8 Comments

Do ADUs actually provide housing?

It may seem odd to ask whether a housing form actually provides housing, but it’s a key premise in civic debates about accessory dwelling units.

June 18, 2014 · 4 Comments

Why ADUs are hard to study, and confuse nearly everyone

ADUs are a really unusual form of development. This post goes over their special qualities, and explains why a lot of “debate” about ADUs is so repetitive.

June 11, 2014 · 11 Comments

Research and policy about accessory dwelling units: introducing a 13-part series

Which hopes and fears about ADUs are most likely to be true? Explore claims and controversies with new evidence, in this 13-part series, beginning today.

June 4, 2014 · 19 Comments

Are Tiny Houses and ADUs the same thing? Not always, but they’re really good friends

Boy, you know it’s been a great day for the website when Carpet Carl tweet-checks it! A few days ago, a post about ADUs by Michael Andersen on bikeportland.org got … Continue reading

March 1, 2014 · 7 Comments

Do lax “granny flat” regulations encourage absentee landlords? Some new evidence from Portland.

Imagine, in the abstract, the absentee landlord. I personally see him as a sort of Dickensian villain, say Sir Mulberry Hawk, coarse in intention despite his fine clothing and mustache, … Continue reading

May 29, 2013 · 6 Comments

Multigenerational homes: accessory dwelling units by any other name

In the past year or two, major builders have accomplished an interesting slight of hand.  They have recognized the need for houses with ADUs, and started selling them for tidy … Continue reading

November 30, 2012 · 4 Comments

Appraisal Journal on ADUs: they could be worth more than you think

Today the Appraisal Journal publishes a research paper about residential properties with accessory dwelling units (ADUs).  The paper describes an income-based method for appraising properties with ADUs, and concludes that … Continue reading

November 20, 2012 · 10 Comments

The many and confusing synonyms for ADUs

A quick note about language here.  One reason people get so confused, and perhaps heated, about accessory dwellings is that language about them is  confused.  The different names conjure up … Continue reading

June 4, 2012 · 23 Comments

My tiny house after 5 years: things I would have done differently

I’ve written here about how well my tiny house is working out — I converted my detached 1.5-car garage to a little “accessory dwelling unit” and have mostly rented it … Continue reading

February 27, 2012 · 7 Comments

A research and action agenda for Accessory Dwelling Units and their advocates

I spent a lot of 2011 learning about Accessory Dwelling Units (also known as in-law units, granny flats, backyard cottages, etc).  Beat that in terms of geekiness!  (Okay, I bow … Continue reading

January 10, 2012 · 8 Comments

Appraising properties with accessory dwelling units: a preview of new methods and findings

[update Nov. 2012: the paper, including updated results, is out in Appraisal Journal… click here] This year I’ve been working with appraiser Taylor Watkins of problem of appraising properties with … Continue reading

December 21, 2011 · 15 Comments

“Understanding and Appraising properties with Accessory Dwelling Units (ADUs)” – a free seminar December 16, 2011 in Portland

[EDITOR’S NOTE: this event has already occurred! For a synopsis of results, click here.] (for an emailable PDF of this invitation, click here) A presentation for real estate, building, and … Continue reading

November 21, 2011

How appraisals and “GSEs” make financing an ADU challenging

(Update January 2013: please note that the research on which the following piece was based has now been published in Appraisal Journal.   Please read the full text of that article … Continue reading

November 21, 2011 · 11 Comments

Can ADUs solve our McMansion problem? Or maybe the other way around?

Accessory dwellings don’t often get a thorough discussion in the media these days, because most writers (and most Americans) are still getting used to the basic idea of them.   We’re … Continue reading

November 10, 2011

My garage apartment — a place that redefines family

I’m pretty much an obsessive planner when it comes to big projects.  I researched and penciled out a lot of scenarios before I developed my garage into a little apartment, … Continue reading

October 29, 2011 · 11 Comments