Accessory Dwellings

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

Derin & Andra William’s ADU: An Energy-Efficient Basement Apartment

Williams ADUQuick Facts

  • Setting: urban
  • Neighborhood: Rose City Park, Portland, Oregon
  • Type: basement conversion
  • Use: rental
  • Square Footage: 650
  • Year Built: 2012
  • Owner: Derin & Andra Williams
  • Designer: Derin & Andra Williams of Shelter Wise
  • Builder: Derin Williams of Shelter Wise
  • Total Material & Permit Costs (does not include owners’ sweat equity): $60,000

“We love our ADU and we want to do more of them. We decided to build our ADU partially because I always like to do things on my own first to make sure I know what I’m doing before I help someone else. Now that we’ve built our own ADU we want to help other people make it a reality.” – Derin

the kitchen is bright and airy

the kitchen is bright and airy

Derin and Andra Williams bought their 1920s bungalow in Portland’s Rose City Park neighborhood with plans to convert the basement into usable living space. Derin explains, “I really like basements. Whenever I go into a house I always want to look at the basement. So much potential.” Andra chimes in “He’s a hobbit!”

The couple realized that if they were going to a do a full basement remodel, including a seismic upgrade and new bedrooms, a bathroom, and recreation space, it would make sense to add a kitchen as well to create a fully self-contained unit. Portland had recently waived System Development Charges (SDCs) for ADUs. (Fortunately, the SDC waiver has been extended though July 2016.) Andra and Derin researched ADUs and were convinced to create one in their basement because it would create housing flexibility, enable them to have family close by, create community, and provide income potential.

a 1940s kitchen was salvaged and reinstalled here

a 1940s kitchen was salvaged and reinstalled here

As they designed their basement ADU, Derin and Andra were inspired by a trip they had taken to Uganda. Andra explains that in the Ugandan village where they stayed, often three and sometimes four generations of family members live together on one property, sharing resources. Derin added that people lived in close proximity to each other – “sometimes just feet away from their relatives’ houses” – which provides opportunities to share child care, food, and farm work. Andra was also inspired by the efficient use of space in the dwellings and the use of natural materials. Simplicity, efficiency, and community became their guiding principles for their basement ADU.

“We wanted it to be seamless going from upstairs to downstairs to provide housing flexibility. That way if we sold the house and someone wanted to use the ADU and the main house as one big house, all they would have to do was open a door. We matched the molding, colors, hardware, and doors from the main house in the ADU.” – Andra Williams

the bathroom sink is salvaged and the vanity made from cabinet-grade plywood scraps

the bathroom sink is salvaged and the vanity made from cabinet-grade plywood scraps

In addition to the aesthetics, there were practical design considerations at work. Derin located the bathroom of the ADU directly below the upstairs bathroom to make plumbing easier. They relocated the washing machine and dryer from the basement to a shared space between the ADU and the main house. There was also a need to bring in good natural daylight, so Derin and Andra added 6 windows in the ADU, including 3 egress windows.

Derin has a background in energy efficiency, so it was important to the couple that the ADU incorporate as many sustainability features as they could afford. Their sustainability efforts began when they decided to convert existing space and retain as many components of the structure as possible. They reused the original posts and beams as well as the existing concrete floor. They were grateful that the city was willing to grandfather in the existing staircase rather than requiring them to replace it. They incorporated green building materials including energy-efficient windows, Roxul insulation for sound dampening between the rooms, closed cell soy-based foam for the walls, an open-cell soy based foam for the ceiling, low VOC paints, and an energy recovery ventilator. They ground down, stained, and refinished the existing concrete floors. They also incorporated several salvaged items. They purchased a bathroom sink from the ReBuilding Center and a friend built the vanity out of scrap cabinet-grade plywood.

“We also reused a 1940s kitchen completely. I was doing an energy audit down in Eugene and they were removing the kitchen so I asked if I could have it. Fortunately, they agreed and now it’s our favorite part of the ADU.” –Derin Williams

The head height requirement turned out to be the biggest regulatory challenge Derin and Andra encountered as they built their ADU. They realized that they would either have room to drop the ceiling for soundproofing purposes or to add a finish floor over the concrete. They didn’t have room to do both within the minimum height requirement, so they decided to prioritize soundproofing.

the concrete floors were ground down, stained and finished

the concrete floors were ground down, stained and finished

“We could have done ceiling sheetrock right up against the existing floor joists and we would have been able to put down a finish floor, but we wouldn’t have the sound proofing we were looking for between the ADU and the main house. So we instead used resilient channel and hung our sheetrock about a half inch below that and used ¾” sheetrock. Soundproofing was a huge learning curve because you have to be a perfectionist when you’re soundproofing. If I had it to do over again I would supervise the sheetrockers. They used the wrong screws, which were too long.”– Derin Williams

Like so many other families, Andra and Derin also struggled to stay in budget on their remodeling project. They funded their ADU with savings from selling a previous business.

the master bedroom

the master bedroom

“Our budget was $50,000 and we spent about $60,000, which doesn’t count our sweat equity. The cost to have it done would be more in the ballpark of $82,000. Our egress windows were expensive because we opted for a high-end window and concrete window well. We could have done them cheaper if we went with different windows and window wells, but we stuck with what we wanted. I’m glad we did. The ADU is a quiet place to go. It seems like an escape and it’s amazing for sleep. Both our son and I need very dark, quiet environments so it works really well for the 50% of the time we’re sleeping!” – Derin Williams

When I asked what the highlight of their ADU build was, Derin laughed and said:

“Probably when I met Bobby. Bobby moved in next door and he didn’t know what he was getting into when he moved in next to us! He’s a contractor. In the middle of the build our son, who was a one-year-old at the time, was in the hospital for 2 weeks. I needed help, so I filled out checklists and Bobby came over and completed them for me. Bobby was probably the highlight.” – Derin Williams

kid's room

Andra & Derin’s son’s room

Andra and Derin were grateful that their community rallied around them during this difficult time. Initially, they anticipated that they would move into the ADU and rent out the main house, but while their son was ill they were grateful that no one had moved in yet. They were able to have family members come stay with them and grateful to have space for everyone. For the past year their son has been healthier and they’ve had the whole house to themselves. Half their home is used as office space for their home-based business, Shelter Wise, which specializes in energy-efficiency and small home construction. They find that they use parts of each of the units. They sleep in the ADU where it’s quieter and they cook in the main house. However, they plan to move into the ADU completely this summer and rent out the main house.

shared laundry facilities

shared laundry facilities

“I don’t think there’s anything I don’t like about the ADU. Other than the guilt of how I feel like we’re wasting space. But we appreciate having the flexibility that it offers. We use parts of each house, which is not at all what we envisioned. We basically use the 2 bedrooms in the ADU and our bedroom is too big!” – Andra Williams

So what advice do Derin and Andra have for someone considering creating an ADU?

“Go through the full bid process from the get-go as best you can. You can’t do everything right off the bat unless you have detailed plans. Do your homework. Know the costs and have alternatives. Know the quality of your foundation. If you are going to do a basement ADU worry about the sound from above because it is loud and most basements are only 7 foot tall or less, so your head is only a foot and a half away from people walking on hardwood floors above you. Consult a soundproofing expert.” – Derin Williams

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.

12 comments on “Derin & Andra William’s ADU: An Energy-Efficient Basement Apartment

  1. Martin John Brown
    March 29, 2014

    This is one of my favorite projects on the site. Maybe it’s not the fanciest, but it shows how a lot of the likely benefits of an ADU can be achieved for a workable price. I love how the owners put a lot of thought into quality of life decisions — for example choosing soundproofing over a finished floor. And the flexibility they describe — having the place for relatives, or a rental, or extra space when they need it — sounds like a great aid to household peace and stability. Thanks for all the details!

  2. Pingback: Stradivarius violins and cigar box guitars (How much does an ADU cost?) | Accessory Dwellings

  3. keridouglas
    May 10, 2014

    Great feature story! I am curious to know more about the energy efficiency. How is the ADU being heated and cooled? Any recommendations? Or – is this a passive energy use space? What type of appliance were selected? Thanks!

    • linamenard
      May 10, 2014

      Dear Keri,

      Thank you for your inquiry! I’ve passed your message along to the ADU owner so that he can address your questions.

      Lina Menard
      ADU Case Studies Coordinator

  4. derin
    May 10, 2014

    The basement ADU is heated with a comb, zonal baseboard hydronic wall heater ( which means each room has its separate programmable thermostat and a gas stand alone stove. We don’t actually turn the heat on very often. The floor tends to be cold (nice in the summer and not in the winter) we decided that digging out our concrete floor and insulating the slab/ installing an in floor hydronic heat was cost prohibitive and slippers take care of discomfort in the winter. We also installed a Panasonic Energy Recovery Ventilator for ventilation. Ventilation is required as we did a blower door test and the space is extremely air tight (1.5 ACH50 for those geeks out there). Come check us out on the ADU tour and get a bunch more information about the energy efficiency.

  5. derinwill
    May 10, 2014

    We use zonal hydronic baseboard heaters and small gas stand alone stove. We also have an Energy Recovery ventilator made by Panasonic to capture some of the heat during the ventilation process. I do blower door tests for work so during the construction we used the blower door to make the space very air tight, then we added mechanical ventilation (ERV) so we could control over how much fresh air/ filtration we wanted. (for those geeks out there the space is 1.5 ACH50). Come check us out at the ADU tour we will also have a modern tiny house there as well.

  6. Pingback: Joe Hermanson’s ADU: A Daylight Basement Rental | Accessory Dwellings

  7. Brent
    August 20, 2014

    Hi. We enjoyed touring this ADU during the ADU tour. I forgot to ask Derin: what was the ceiling height before and after the project? Our basement ceilings are about 6’9″. I’m just wondering if we would be able to do the ceiling finish required by the code (which is apparently 3/8-1/2″ sheetrock), maybe some soundproofing, and still meet the 6’8″ requirement. Thanks.

  8. derin
    August 28, 2014

    The ceiling height before was 6’10” to 7′ throughout, the floor is not perfectly level (another challenge with many basements), we used 1/2″ resilient channel and 3/4″ SoundRock. By the way I am pretty sure that code requires 5/8″ on the ceiling and not 3/8″ or 1/2.” Thanks and best of luck in your basement remodel!

  9. Matt McComas
    April 6, 2015

    Derin, We have a very similar situation with an existing staircase that doesn’t have great headroom in an old house here in PDX. I’m curious if the city let you keep the staircase because it met the 6’2″ clearance (grandfathered in)? Did you get it cleared with the city before you pulled the permits for the rest of the basement?

  10. linamenard
    April 12, 2015

    Dear Matt,

    We checked in with Derin and here’s his reply: “We had to do some alteration the bottom of the stair landing as the last step had a rise of 2″ more then all the rest of the steps, the height off each tread was over 6’2”.

  11. Pingback: Tips for Basement to ADU Conversions | Accessory Dwellings

Comments are closed.

%d bloggers like this: