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ADUs’ Tiny Relatives

Editor’s note: In a stunning turn of events, Portland has actually moved ahead with some of the ideas described in the post and video below, temporarily ending enforcement of the habitation of mobile dwellings on residential properties. Read more about this update in the City’s of Portland’s Bureau of Development services official press release on this.  10/16/2017.

Here’s the original post from November, 2016.


There’s a lot of half-baked information about ‘tiny homes’ available on the web and on TV, which leads to confusion and misunderstanding about the differences between ‘ADUs’ and ‘tiny houses on wheels’. I find myself explaining the differences frequently.

This confusion is largely attributable to media coverage that conflates ADUs and tiny houses on wheels as ‘tiny homes’. I’m a fan of both of these types of small housing, but they are extremely different housing products, and I now use the terms “ADUs” and “tiny houses on wheels” when discussing each of them to dispel general confusion about the two dwelling forms.

Last week, a vandweller named Dylan Magaster came to shoot and produce a video about my business, Caravan-The Tiny House Hotel. The video succintly captures a lot of what we’re trying to do with Caravan in terms of our broader mission around small housing.

But, more specifically, Dylan did a great job at using the video to convey the differences between the two housing forms. So, I’m going to take this opportunity to a) share this video with readers of and b) to provide answers to some FAQs about the differences between tiny houses on wheels and ADUs.

Frequent questions about tiny houses and ADUs:

Q: Can I just take the wheels off of a tiny house on wheels and turn it into an ADU?

A: Theoretically, yes. But, this is a silly way to go about developing an ADU.

Here’s some of the practical reasons why most tiny houses on wheels would be difficult to convert to a legal, permitted ADU.

  • tiny houses on wheels typically don’t have adequately tall bedrooms in the sleeping lofts due to height constraints of vehicles
  • the lofted bedrooms can’t be accessed by a legal, to-code staircase
  • the insulation in a tiny house on wheels typically won’t meet minimum insulation standards that code requires
  • the dwelling must be placed on, and then structurally fastened to, a permitted foundation
  • engineered calculations must specify how the permitted structure must be fastened to a foundation, how the posts and beams must be braced, and how it must be sheathed
  • the mechanical, electrical, and plumbing would have to re-exposed and reinspected
  • the structure may have to meet aesthetic standards on the exterior facades

Q: What can’t a tiny house on wheels just be an ADU?

A: ADUs are built to standard building codes, including foundations that go down below the frost line, and are then tied into utility grids, using regulated protocols and licensed professionals, including plans examiners in a municipal building department, a local utility company, and licensed mechanical, electrical, and plumbing technicians.

From a planning/zoning perspective, tiny houses could theoretically meet the architectural standards that an ADU must meet in terms of size, exterior look, and placement on a lot. But, to my knowledge, only Fresno, California has actually allowed for tiny homes on wheels to be classified as a legitimate architectural form for an ADU.

Q: Why can’t a tiny house on wheels be on my property? What gives?

A: Well, actually, in many places, a tiny house on wheels can be on your residential property. The problem is it can’t neccesarily be legally hooked up to sewer and water utilities, and municipalities typically specify that in residential zones, people must live in permitted residential structures. Tiny houses fall into the same category as other non-permitted alternative dwellings such as campers, RVs, tents, and yurts.

So, depending on local zoning regulations, it is quite possible that you can legally park a camper, RV, or a tiny house on wheels on a residential property, or have a tent or a yurt on the residential property. It’s just that, according to the zoning & building regulations, no one can actually occupy those dwellings.

However, plenty of people ARE occupying such dwellings on residential properties. I appreciate people who live in such dwellings. I view this as a form of gentle civil disobedience (even if they don’t). Without rule breakers, artificial regulatory boundaries would tend to calcify, and the interpretation of regulations would grow ever more thoughtless with no regard to the original intention underlying the regulation.

Despite the fact that these non-permitted dwellings are truly more sustainable, efficient and affordable types of dwellings, municipal codes aren’t flexible with regard to what constitutes a viable dwelling structure on a residential property.

In defense of building code regulations, there are perfectly reasonable arguments to be made about why building codes are important to protect human health and why zoning codes help to maintain civility and order.

There are also perfectly reasonable arguments of how the building and zoning codes actually lead desperate people to try to find some sleep in seemingly unsafe, unhealthy, and unsanitary conditions illegally in tents under noisy interstate bridges.

It would be nice if more cities took some proactive measures to allow for camping in unpermitted dwellings in residential zones. Eugene, Oregon did just this over a decade ago with their Permitted Overnight Sleeping (Camping) code.

Speaking with one of their city planners a couple weeks ago, I learned that Eugene hasn’t had any significant neighborhood pushback or political issues with their camping code since its inception. They even allow RV hookups on residential properties, so it’s possible to live in a tiny house on wheels there, and to be fully hooked up to utilities.

It makes me wonder why so few cities have tested out this simple regulatory approach. This solution to providing affordable housing is a penstroke away.

Meanwhile, there’s still plenty of work to be done within a more formalized ADU code. For now, while ADUs remain the only legal market-based pathway to develop small infill housing on residentially zoned properties, I’ll be focusing my bandwith there. I am currently working on a book about ADU development and hope to make it available in the not-too-distant future.

About Kol Peterson

Kol is an ADU consultant, advocate and author of Backdoor Revolution: The Definitive Guide to ADU Development. Read more here: and learn about building your own at Email at


This entry was posted on November 22, 2016 by in Policy & Trends and tagged , .
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