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Carolyn Matthews & Bruce Nelson’s ADU: Granny’s Garden Cottage

Nelson-Matthews ADU

Nelson-Matthews ADU

Quick Facts

  • Setting: urban
  • Neighborhood: Cully, Portland, OR
  • Type: stand-alone detached unit
  • Use: furnished rental (Granny’s Garden Cottage)
  • Square Footage: 640
  • Year Built: 2006
  • Owner: Carolyn Matthews & Bruce Nelson
  • Designer: Michael Wolfe
  • Builder: Dave Rush of Dave Rush Design-Build
  • Total Cost: $260,000
“‘Granny’ was a resident of this property many years ago, who we know of through her family. Friendship with that family is how we came to enjoy what for 34 years we’ve called Granny’s Place.” -Carolyn Matthews
Nelson-Matthews ADU Living Room 2

Nelson-Matthews ADU Living Room 2

Bruce Nelson and Carolyn Matthews first learned about ADUs by participating in green building tours in Portland, Oregon. Carolyn and Bruce have lived on their property in the Cully neighborhood of Portland, Oregon since 1978. Since then they have created a garden oasis and developed strong relationships with their neighbors. So they liked the idea of aging-in-place on their own property.

Creating an ADU appealed to them because it could provide additional income and flexibility as their housing needs change. Bruce and Carolyn funded their ADU by converting their inheritance and retirement funds to pay for it. They took down an existing shed in order to create space for their Detached Accessory Dwelling Unit, which they affectionately refer to as their DADU.
Nelson-Matthews ADU Roll-In Shower

Nelson-Matthews ADU Roll-In Shower

As they began designing Granny’s Garden Cottage, Carolyn and Bruce were inspired by the small, accessible homes they discovered when they did research at the library or went on green building tours. Their architect Michael Wolfe also provided inspiration and considerable knowledge about green building and accessibility.

Their biggest challenge was complying with the city limitations on square footage. Their main house is 920 square feet and, at the time they applied for an ADU permit, homeowners could build an ADU that was 1/3 the square footage of the main house, but no more than 800 square feet. So they could either legally build an ADU of 307 square feet or apply for a variance to go bigger. Their original submitted design for an 800 square feet was rejected, so they appealed and consulted with the Planning Bureau, which suggested they come in with a new design at 2/3 the square footage of the main house. They paid the appeal fee and the appeal was granted for the design of the existing ADU. (The current regulation limits ADUs to 75% of the square footage of the primary dwelling, so if they applied for an ADU permit now their ADU could have been 690 square feet.)
“At the time, the fact that our main house was small reduced the allowable size of the ADU unless we challenged the ruling.” -Bruce Nelson
Nelson-Matthews Courtyard

Nelson-Matthews Courtyard

Another factor influencing the size and shape of their little home was their desire to protect a nearby deciduous tree. They knew that if they wanted the magnificent Japanese pagoda tree to shade the courtyard between their primary dwelling and the ADU they would need to be careful about protecting its roots. In addition to these footprint limitations, Bruce and Carolyn were interested in universal design elements that would enable them to age-in-place. Their design includes a wide hallway, a roll-in shower, and a countertop with a top that raises and lowers to accommodate wheelchair users.

Nelson-Matthews ADU Kitchen

Nelson-Matthews ADU Kitchen with Counters High

Sustainability was another driving factor for Bruce and Carolyn’s ADU. They knew that attention to energy efficiency would provide environmental and financial sustainability. So Granny’s Garden Cottage includes a variety of green building features, including advanced framing for the walls, structurally insulated panels for the roof, on-demand water heaters for domestic use and radiant floor heat, double pane windows with argon gas, a heat recovery system, local wood for the kitchen woodwork, salvaged wood for the bathroom cabinets, and option for rain water harvesting and treatment for use in the building, and low VOC paints and plasters.

“My favorite features are the color and the quietness of it. The building is comfortable to be in and glows with the feeling of warmth.” -Bruce Nelson
Nelson-Matthews ADU Kitchen with Counters Low

Nelson-Matthews ADU Kitchen with Counters Low

As they designed their home, Carolyn and Bruce anticipated that it could be used in a variety of ways. It could used as a short- or long-term rental, could serve as a space for projects, and eventually they could live in it. Bruce and Carolyn currently rent their ADU as a furnished rental and suspect they will continue with short-term rental for the foreseeable future.

“My favorite thing about having an ADU is that it gives us options.” -Bruce Nelson
Several friends and neighbors have used the space over the years for periods as short as an overnight or as long as 2 1/2 years. Their guests with limited mobility are particularly appreciative that that ADU is accessible. Bruce explains that the level of interaction between the residents of the primary dwelling and ADU varies quite a bit.
Nelson-Matthews ADU Bedroom

Nelson-Matthews ADU Bedroom

“When our neighbors lived in the ADU for 2.5 years while renovating their home, we had frequent contact and meals. For short term occupants, the interaction is much less frequent.” -Bruce Nelson

Carolyn & Bruce’s ADU has been featured in a handful of articles including “A New Place to Grow Old” in the Oregonian, “Peek into Portland’s Small Homes” in OPB’s Ecotrope, and “My Summer Garden Cottage” on Granny’s Garden Cottage has also been on ADU tours, including the Pedalpalooza ADU Tour.
“We’ve been surprised how many other people really love the building.” -Bruce Nelson
Nelson-Matthews ADU Great Room

Nelson-Matthews ADU Great Room

Bruce says that the ADU is bringing in sufficient income to cover short-term expenses and operating costs, but it is not contributing to help cover the cost of its construction. Their home was quite expensive per square foot because they were early adopters of several green building techniques. Of course, every pioneering home, no matter how well thought-out, has at least one thing the owners would do differently if they could do it over again. For Bruce, that would the rainwater system.

“The rainwater recovery system has been quite worrisome over time. If we could do it over we would have connected the rainwater system to the main house roof and likely brought in rain water consultants from out of town.” -Bruce Nelson
When I asked Bruce if they have any plans to move or sell their property in the next ten years, he replied:
Nelson-Matthews ADU Living Room

Nelson-Matthews ADU Living Room

“No, not at all. We love our neighborhood, our garden and our home. Due to the larger size of lots in our neighborhood, I expect more infill to occur. Some of it will likely be accessory dwelling units. On our 5 block long street, with maybe 50 residences on it, I am aware of current properties with ADUs plus an additional 1 that will soon be in place.”

So what advice does Bruce have for homeowners considering creating an ADU on their property?
“Consider who you are targeting by your construction. Is it only able-bodied people who can handle steps? Is it just young folks with few worldly possessions? Is it frail elderly? Is it children?” -Bruce Nelson

About linamenard

Hi. My name is Lina Menard and I'm a small house dweller, designer, blogger, and builder. I'm currently collecting ADU Case Studies for Through my company Niche Consulting LLC, I help people design and build the home (and life) of their dreams! I also tell my stories about simple living in small spaces - like a travel trailer, a yurt, a backyard cottage, and tiny houses on wheels - at Niche News.

5 comments on “Carolyn Matthews & Bruce Nelson’s ADU: Granny’s Garden Cottage

  1. Martin John Brown
    March 14, 2014

    This is a beautiful building that has a lot of high quality features and undoubtedly has long term value. So many people would love a place like this in their backyard! But given the simple layout, I think most people would be shocked at the price… >$400/sf. The article puts the cost partly to being early adopters of technologies.

    My gut feeling is that stand-alone ADUs are likely to be fairly expensive per SF, that’s just the nature of installing all the systems. But I’ve read of several extremely green small houses done for less than this. Should readers take this price as typical? How much would it cost now?

    Thanks much to Carolyn and Bruce for relating their story.

    • Bruce nelson
      April 5, 2014

      The costs to construct the building were indeed high. Costs that we include in the $260,000 construction cost include architect fees, landscaping, city development fees, taxes from converting retirement savings to money for immediate use, consultant fees, demolition costs, furniture/appliances for the new structure and the usual general contractor charges. It seems more realistic that all of these costs be included in construction. If you take out a 15 -year mortgage, then obviously the interest costs you pay over that time period should be reflected in what it costs you to build the house. Yes, it is true that we chose to select what we thought were quality features. I hope that our price is not the price that needs to be paid. But for us, it was the price to get what we wanted in the site we wanted and in the time frame that we wanted.

  2. Martin John Brown
    April 5, 2014

    Hi Bruce, thanks so much for chiming in with the additional information! I heartily agree, we need to be more realistic about construction costs, which are chronically under-quoted, and one of my goals for this series of posts was to find out what really needs to be paid. I very much appreciate getting the “real deal” from you. So far what I seem to be finding out (there will be more data on this published on the site in a month or two) is that attached ADUs are considerably cheaper than detached — but that people want to build detached ones anyway, even if it stretches finances. I think the backyard cottage, as your place so nicely demonstrates, is a kind of ideal to which many people aspire. Reaching that goal is more important, to many people, than simply finding the most economical project. Of course it all has to pencil out somehow, but I’m not feeling like a lot of people go for the absolute minimum. Nice place, by the way. 🙂 -Martin

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