Accessory Dwellings

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

Ten ADU Aspirations for 2015. Let the countdown begin!

As we all know, New Years is a time to conjure up lofty ideas.  Here are a few great ideas that we, the editors of, probably won’t have the time to work on, but would love to see others try in 2015. Any one of these ideas could work, all would add vibrancy to neighborhoods, and some could pan out to be quite profitable. You read them here first! But we must admit: ideas are cheap; making them come to life is the challenge.

Ideas for Homeowners

(10) When starting on your ADU design, funk it up. Consider post and beam construction, cob interiors, strawbale insulation…  There are plenty of ways to make great, modern interiors. Although many cities regulate the exterior appearance of ADUs, they usually leave a lot flexibility for the building’s shape and are silent on how the interior looks. So, be creative with the confines of the code. A good designer should relish in this challenge.

Ideas for Developers or Neighbors who all want ADUs

(9) Develop a community-esque ‘pod’ of alley ADUs on adjacent properties. This would be darling. There’s intriguing historic and social roles that alley ADUs have played in the US. It’s a shame that the kind of charming and unique alleyway character found in old cities around the world can’t be found in the US much anymore. Pods of alley ADUs would be a great way to restore life and appeal to underused alleys. 2014-12-10 09_05_57-Pinterest There’s a visual charm to the scale of alleys dwellings that is contextualized to the match the architectural fabric of a city Ideas for Designers and architects

(8) Don’t feel compelled to reinvent the wheel on interior layouts.  Prefabricated ADUs haven’t panned out as a marketable product so far in Portland or other cities we’ve checked with (probably due in large part to design code regulations requiring new detached ADUs to match the main house). This makes ADUs more likely to be unique (which, we actually like). However, there are some particularly awesome floor plans that seem to work well in many of the ADUs we’ve seen. Successful layouts can be riffed on again and again. One nice design for a detached, cottage-style, one-bedroom ADUs is an open first floor, with a lofted bedroom over half of the ground floor. Beneath the loft are exposed beams with some kind of decking above them. Designers can iterate from this layout as their base design for 1BR detached ADUs. Exterior style and finishes can be selected pretty much independently, subject to design code requirements. Concordia ADU_LEVEL 2.jpg A typical lofted floor plan by Polyphon Architecture and Design After viewing enough above-the-garage ADUs, basement ADUs, and 2BR ADUs, other ‘best practice’ layouts may emerge for each of them.

Ideas for Entrepreneurs and Developers

(7) Note: The following strategy is not for the average homeowner, but rather an idea suited for small scale developer types. Condo-izing ADUs offers an opportunity to make an immediate return on ADU development. Although it’s admittedly a bit more complicated, this model allows different people to own (and independently finance) the main house and ADU on a single lot. This can help meet demand from home buyers for highly desirable small, detached homes costing less than half as much as a typical single family dwelling (In Portland, condo-ized ADUs in neighborhoods of $400K+ 3BR/4BR homes sell in the $150-$250K range). There’s a huge demand for close-in housing at this size and price point, and this is one way to provide it. Here’s a recent ADU sold as a detached, stand-alone condominium unit. 4522 NE 19th Ave # 2, Portland, OR 97211

This ADU is part of a little housing community that was developed by Eli Spevak, the owner of Orange Splot and an editor of this site. Whereas backyard cottage-style ADUs in today’s Portland market might add $100K of contributory dollars to a property (though your mileage may vary), they apparently sell for about twice that amount in today’s market as condo-ized ADUs. The one shown above sold for $226K and another one sold for $195K. Opportunity knocks. Based on the two examples of ADUs recently sold as condos, we believe that this model could pencil out well for an entrepreneurial small home developer.  We’re excited to see what creative financing models, landscape and community-scape and architectural designs emerge using it. Although there’s potential that cookie-cutter designs might be tempting with this model, we have hope that beautiful, one-of-a-kind, contextualized ADUs could pencil out better since they’d be more desirable homes to buy. Although this ADU development model could be speculative, as described above, it can also allow friends or family members to own homes on a shared lot – each with their own financing.  Either way, condo-ized ADUs could run in parallel to the existing owner/developer ADU ownership development model that has flourished in Portland since the SDC waiver kicked in 2010.

Ideas for Designers and Developers

(6) Give a “Snout House” a nose job.  Developers have built countless homes with large garages out front, especially since the early 1970’s.

Dean Terry, still from the documentary film Subdivided (ADU text added)

Wouldn’t it be wonderful – and a great design challenge – to house people instead of cars by converting these 2-car proboscis garages into darling little homes?  As a bonus, people pay rent, whereas cars (or shelves upon shelves of rarely-used personal possessions) typically don’t.  Whoever figures out how to pull off these conversions successfully will have plenty of properties to work with, and will add an important tool to the ‘retrofitting suburbia’ toolbox.

Ideas for Designers and Engineers

(5) Develop a staircase that meets code, but will fit a variety of tight inclines. Alternating tread stairs don’t usually meet code, but they really seem to do the trick in small spaces like ADUs. Getting a steep and smaller-than-usual staircase design to meet building code would be helpful since, as it stands now, many ADU owners struggle with how to fit a code stair in a small, and height-restricted building envelope without ruining their floor plan. An example of a modular and steep set of customizable alternating tread stairs that can be special ordered through Lowes to access a lofted bedroom.

Ideas for Financiers

(4) Develop a private equity fund for homeowners eager to build ADUs, but who don’t have the capital to do so. Loans would be secured by the property and repaid through rental income generated by the ADU. This would be a valuable supplement to the admittedly few conventional ADU loans products that currently exist.

(3) Launch a 2nd mortgage product for ADUs, based on the as-completed value of the ADU and main house.  The lender would also take into consideration additional income the ADU would generate for the borrower. A few banks already offer something like this as a first mortgage, but many homeowners are looking for better options because they don’t want to lose their super-low first mortgage rates or pay loan origination fees twice.  This type of loan would inevitably be priced a bit higher than standard first mortgages.  But it could be a win-win for innovative lenders and ADU owner-builders.

Ideas for Planners

(2) Allow more than one ADU on a single family lot.  Vancouver, BC allows a house on a single family to have both an internal ADU (‘secondary suite’) and a detached ADU (‘laneway house’).  US cities could follow suit. This could go one step further…  Given that new single family homes are averaging ~2,400 square feet and most ADUs are in the 700-800 square feet range, an innovative city could give builders the option to construct 3 ADUs instead of a main house on a standard residential lot.  Each ADU would have to meet height, size, setback, parking, and design compatibility requirements (to each other) of typical ADUs.  Neighbors might prefer 3 small homes to one huge one, and the economics might work quite well in neighborhoods where demand for smaller homes greatly exceeds supply.  Of course, there’d need to be a new name for these things since they wouldn’t be ‘accessory’ anymore.  But we’re sure planners could come up with something that would work just fine, perhaps from this list.

(1) Go ever smaller: Legalize tiny homes on wheels.  Work out a reasonable planning/zoning code for mobile dwellings on residential properties. This model has the potential to open up a new, on-demand, flexible and affordable housing marketplace.

Dee Williams’ tiny house on wheels, from Tiny House Talk

Ideally, this code would allow a homeowner to apply for permits to provide space for habitation of non-permanent mobile dwellings on residential properties. The planning department could set regulations such as minimum parking pad width, and requirements for tall fences to obscure the mobile dwellings from view from neighboring properties. The building department would be involved in ensuring safe, sanitary, and code-compliant sewer, water, and electric hookups. In fact, these infrastructural code standards already exist for RV parks; they’d just need to be transferred to and streamlined for residential applications. The building department would not regulate the dwellings themselves since they’re both temporary and mobile. The responsibility for the mobile dwelling standards would fall to the homeowner and their insurance provider.

A different approach would specify performance measures (ie. egress windows, smoke detectors, functional heating system…) that any tiny structure on wheels (or not) would have to meet in order to be used for habitation.  This would provide a legal path for safe, sanitary and affordable homes in the under-200-square-foot range.  In many cities, this would represent a much-needed market-based form of affordable housing at a price point lower than anything else out there (except for deeply subsidized rental housing).

Tiny homes on wheels have been left stranded as aliens in strictly regulated municipalities. It’s time to bring them into the light in a reasonable and flexible way so that creative and affordable housing options can emerge in cities with affordable housing shortages. We’ve all spent time in spaces that didn’t conform to traditional building codes (tents, RVs, tree houses, forts, caves). It would be great to see more regulations that allow homeowners to help create more affordable housing options without living in fear of breaking the law. For broader perspective on how we slowly expunged cheap housing choices in cities, we’d recommend Alan Durning’s take on Legalizing Inexpensive Housing.

So, that’s what’s in our 2015 cauldron of ADU hopes, ideas, and dreams. Have a great 2015 and may you help one of these ideas come to pass, or materialize one of your own ADU dreams in the New Year. This post was authored by Kol, Eli, and Martin, editors of this site.  Happy 2015!

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
%d bloggers like this: