A few years ago I had the opportunity for my mother-in-law to move in with my family in our NE Portland home. We didn’t have space in our home for her, and even if we did it seemed like giving her some privacy and personal space would make the situation better in the long run.
We decided to build a 200 square foot tiny home that would be largely self sufficient (with a bathroom and kitchenette), but that would rely on the main house for supplementary functions (storage, laundry, major cooking). When we started the permitting process the ADU System Development Charges (SDCs) were not waived as they currently are until 2013 in Portland. Otherwise the costs are ~$12,000+, so we opted to create the building as a Detached Bedroom. This approach has pros and cons.
ADU vs DETACHED BEDROOM
The main difference between an ADU and a Detached Bedroom is that an ADU counts as additional density to the city, whereas a Detached Bedroom is considered an addition to the existing house. A Detached Bedroom cannot be rented out as a standalone apartment nor can it be built to function as one. The main way that the city draws this line is the presence of a full kitchen, as denoted by a sink and 220 outlet for a range. That said, this is a distinction that was made during my experiences with specific planners at specific times. City code is up for interpretation and I would strongly suggest taking any proposal in to the city and reviewing it with a planner early on in the process. In my project the sink is removed from the bathroom and serves double duty as a lavatory and a kitchenette sink. If you have two sinks in a Detached Bedroom I’ve heard that it is necessary to sign a covenant with the county that you will not rent it out. This configuration seemed to me the closest one could come to an ADU. No full kitchen and an inability to rent it out are two large marks against the Detached Bedroom, so why build one?
The biggest reason for me was cost. SDCs would have constituted 1/3 of the budget. It is inexplicable to me that you’d have to pay SDCs twice for an ADU and a 2 bedroom 1 bath house, but only once for a 5 bedroom 4 bath house. Another reason is design. There are strict regulations on the size, height, and placement of ADUs and how they relate to the main house. With a detached bedroom there are no regulations that wouldn’t apply to a normal house (size, height, lot coverage, etc). You could build a 3 story tower clad in purple sheet metal if you wanted, as long as it didn’t have a second kitchen in it. There are also provisions in the zoning code that the roof pitch, siding, windows, trim and eaves of an ADU need to match the existing house. These restrictions won’t affect many people but can be a problem if one wanted to pursue a modern or less conventional design.
COSTS
The ultimate cost for the tiny house was around $27,000 or $135/sq. ft. I was initially aiming for $100/sq. ft. because it was a nice round number. However, building small is inherently more costly as you have all the utility connections, permit fees, windows, doors, fixtures, etc without the bedrooms and large living areas to spread out the expensive stuff. This was also despite a lot of cost savings, as I did all the design, drafting, interface with the city, also acted as the general contractor and did around half of the physical labor. For the other half I hired a handy friend, as well as subcontractors for the electrical, plumbing and tile setting. Windows were probably the largest splurge (Marvin Integrity fiberglass windows with wood interior) while areas cut back on were asphalt shingle roofing (instead of metal), electric heat (instead of gas), fiberglass batt insulation (instead of anything else).
MATERIALS
A big focus of the design was the materials template. In a small space one has much more intimacy with all surfaces and objects, so making sure they are appealing is an even more important aspect of the design. We tried to use as much salvaged materials as possible and have as few painted drywall surfaces as possible. Instead, the majority of the walls are finished with American Clay and accented with wood and tile. The bathroom did end up being painted as was the exterior trim and some of the interior trim. Salvaged materials include the exterior siding, exterior doors, T&G fir flooring, cabinet doors, tile, interior wood trim and built-in furniture.
In the end the project took around 9 months and was done on weekends and during some Great Recession furloughs. It has been very successful as a way to accommodate a changing family while adding value to our home.
Schuyler Smith is a Papercrafter, Design/Builder and small living enthusiast in Portland, OR.
Schuyler, those are some really interesting points about the distinctions, pros, and cons between ADUs and detached bedrooms. And your point about SDCs (ADU + 2 BR 1 BA vs a 5 BR 4 BA) brings in to question whether any ADU should ever be subject to disproportionally burdensome SDCs.
Nationally, much like Tiny Houses on trailers, ‘detached bedrooms’ may be a useful regulatory loophole for other homeowners to investigate if they are running up against restrictive regulations that are tied to the construction of ADUs in their municipality. Used creatively, a detached bedroom provide the same living functions that an ADU can provide, and can be built at a significantly lower cost.
I can imagine a system for SDCs where there would be a base line amount of square footage and fixtures per lot and then anything above that is pro-rated, although I’m sure that would have flaws as well.
Thanks so much for sharing this, Schuyler, including the budget and the drawings. I’m curious about the heater you chose–what is it, and how is it working out?
But in general, the more I look at the photos and drawings, the more thoughtful this place seems. It’s almost a little class in “what to do right” with a tiny dwelling in accessory mode.
I totally agree about the need for care with materials in such a small space. The users are going to be only a few inches from them all the time. So they have to be good looking, and also very durable (because they’re going to get bonked a lot). In my ADU we spent an absurd $2000 extra for curved concrete counters, but they are just so much richer and deeper than formica it was worth it… the users touch that counter every day.
I note you have fairly large windows in all the primary “living positions” (by the sink and the bed) which can provide some longer views to alleviate the sense of compression in a small house. You’ve got a covered porch (so you can open the door while it’s raining, a must in Oregon). Also there is a filter of planting beds and fruit trees between the accessory structure and the main house–which will give you future opportunities to mix or adjust the balance of privacy and connection between the two dwellings (e.g. by planting or pruning). Living architecture… nice.
Thanks Martin. The heater is a Convectair ‘Apero’ radiant heater. It has no fan so is totally silent, which is very nice. Manual controls though which could be an issue for some users. It is working well and is able to keep up in the winter with no problem. Lastly it has a very slim profile and is comparatively cheap! (~$300)
Yes, the tiny house and it’s windows were positioned to try to give as much privacy as possible given that it is the bedroom of the house as well. One regret is that the windows weren’t positioned better for passive solar heating. Now all we need is some evergreen screening for the winter after the garden is taken out!
Great home and great post, Schuyler! Good point that planners have a certain amount of discretion in whether or not to require execution and recording of ‘second sink agreements.’ I did have to sign one for the Ruth’s Cottages project, where each detached bedroom had a sink outside the bathroom (containing a shower facing a toilet, just like yours).
Hi Schuyler,
I visited your house on the Build it Green tour a couple of years ago, and was intrigued. I’m now considering a similar project and was curious about how much setback (rear and side) you allowed? And what the minimum is? Whatever info you could share, I’d very much appreciate!
Thanks!
Lauren – Glad you liked the project. In typical residential neighborhoods side and rear set backs are both 5′. There are variations for different zonings, alleys, etc… but usually it is 5′ for standard lots. I’m a registered architect so if you come to a point where you need some more help I’d love to hear more about the project! Best of luck.
Hey Schuyler, Thanks so much for your prompt reply! I do have a couple more questions – how can I email you?
I sent you an email with my address, which you can send any further questions so. Hopefully it didn’t get spammed! Thanks.