This article originally appeared on Houzz.com.

First of all, let’s clear up any misconceptions. This is not that kind of group living. Not the 1960s, free-love group living that might first pop into your head when you hear the term. This is more of a clubhouse-style arrangement.

Homeowners Terri Sullivan and Paul Black, who have been a couple for 25 years, and Sullivan’s best friend realized they could get more bang for their buck if they pooled their resources. So the trio added a second story to the 850-square-foot ranch-style home that Sullivan and Black had been living in, and their unconventional living arrangement was born.

Houzz at a Glance
Who lives here: Married couple Terri Sullivan and Paul Black, and Sullivan’s best friend
Location: Phinney Ridge neighborhood of Seattle 
Size: 2,100 square feet (195 square meters); two bedrooms, three bathrooms 
Designer: Tim Hammer of Cast Architecture

Sullivan and Black made some initial interior improvements to the 1950s home when they bought it in 2002. Meanwhile, the friend was living a few miles away in a three-bedroom house that had become a little too big for her. And since she seemed to be over every night for dinner anyway, they all agreed that maybe it made more sense to put a second story on the home and have her move in.

They hired Tim Hammer of Cast Architecture to help design the new space. “They were so comfortable with one another that the design process was more open and fluid than any I have experienced,” Hammer says. “Everyone was able to get what they wanted without any stonewalling or tit-for-tat. Consensus came easy.”

The 1950s home retained its original footprint but gained extra space by way of a 1,250-square-foot second-story addition. Downstairs, the kitchen and dining room flow to a back deck, which gets shade from a cantilevered bedroom.

HardiePanel fiber cement panels with stainless steel fasteners and aluminum trim cover the exterior sides of the public spaces, while cedar accents the private volumes, such as the cantilevered bedroom. Fiber cement panels clad the underside of the new roof. The deck material is tight-knot cedar.

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The kitchen got a new look and layout to better accommodate the bigger group. Homeowner Black handled the electrical work and installed the Wolf range himself. Custom door fronts on Ikea cabinetry create an elegant look on a budget. (The door panels are made of a single piece of wood so the door grain flows from one cabinet to the next.) Large-format granite tiles form the countertops. The flooring are Marmoleum, a natural linoleum flooring.

Hardware: Ikea

The group plans out big Friday-night meals, often eight courses, so the butcher-block countertop was fitted with custom knife holders to keep utensils close by for dinner prep.

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A dining table that can expand to seat 12 occupies a space once used as a bedroom.

Two master suites occupy the second story. Black and Sullivan share the one shown here.

The other master bedroom has corner windows and a blue color palette. Each master bedroom has an attached office (not shown). The friend, a vocal artist, has turned hers into a professional sound booth.

A dramatic light fixture packs a big punch on the entry landing. In one of the master bathrooms, large-format porcelain tiles mix with gray grout and glass mosaic accent tiles.

In the backyard, a rock waterfall that flows into a koi pond helps diminish traffic noise.

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Hammer, the architect, would like to see more homeowners consider a similar living arrangement. “It is my secret hope that people will see this and think, ‘Hey, we can do that with so-and-so,’” he says. “Zoning codes are met. Density increases. The environment benefits. What’s not to like?”