Case Study: COR-TEN Tree House by Colleen Healey Architecture

COR-TEN Tree House, named for its setting in a woodsy Washington, D.C., suburb, is almost unrecognizable from its original form. But that’s not, as is often the case, because it’s been commoditized for resale value. There were serious functional issues to overcome, and Colleen Healey, AIA, unleashed her problem-solving superpowers with artistry and restraint.

The most egregious condition of this 1970s house, on a cul de sac at the end of a gravel drive, was a detached two-car garage that sat directly in front of the house. Its placement not only swallowed the front yard and blocked views to the street, it also confused visitors trying to find the front door. Then there was the overbearing ambiance. Think of the timber-heavy deck houses of that era, and you get the idea. “The whole back of the house is a massive three-story deck with X brace supports, a tour de force designed and built by an engineer,” Colleen says. “It was overdone, with interior exposed roof rafters that went up, dark and heavy. He had completely focused his view on the backyard, which is beautiful, but ignored the front of the house.”

She met the clients while serving on a preschool auction committee with the wife. The couple wasn’t yet ready to renovate, but the three worked on a design over a period of several years until the time was right. “Their kids were at an age where they could play outside on their own, but the front yard was a wall of cedar shingles,” Colleen says. “They needed to be able to keep an eye on the kids from inside the house.” 

Step one, then, was to clear away the decrepit garage and attach a new one on the north end of the bar-shaped house. On top of the garage is a new primary suite, which previously had taken up too much of the choppy main floor. That move allowed Colleen to create flowing living spaces for the couple, who loves to entertain. Two existing lower levels contain the secondary bedrooms.

Physical and visual connections to the land were critical to the program. Previously, a wooden walkway ended at a split-level entryway, the front door opened to a cramped landing midway between the main floor and the lower floor. With the garage out of the way, the front yard was regraded to raise the entrance to the main level, and a flat, sunken lawn was carved out for play and entertaining. 

Along the mostly unchanged rear of the house, Colleen added a three-panel glass slider that pockets into the wall, dissolving the boundary between the living room and an expansive existing deck. “Guests can park on the cul de sac or in the driveway,” she says. “You walk down a boardwalk through the front yard. When there are parties, you can see people coming and can set up for entertaining on the front lawn, throwing the house open from front to back.”

Code Switch

The addition of a primary suite atop the garage resulted in major changes to the entire front façade. A 4-foot-deep bump-out was needed to slide in the new staircase. “We thought about adding the primary suite stair on top of the existing lower-level staircase,” near the center of the plan, “but we wanted to limit anything that would block the view from front to back,” Colleen says. Two stepped dormers add volume above the stair, while a third smaller dormer brings light and height to the foyer. 

The junction of old and new is most evident in the dining room. The old ceiling plane dives down at the center of the table, while the new form shoots up to the sky and opens to the front yard.

 “We borrowed some of that new stair volume for the dining room,” Colleen says. “The dormer windows face west, and both dormers have a roof skylight facing east, so there are dramatic light rays throughout the day.” In a budget-conscious move, the barely-there stair pairs a custom metal handrail with a stock metal stringer and oak treads, which were refinished on site. 

That grid of dark wood ceiling beams in the main part of the first floor contributed to the oppressive feeling. By exposing more of it and painting it white, Colleen used it to define the kitchen and living room. Because the kitchen is in the public eye, she pared back the cabinetry and set the appliances behind flush panels so they disappear. Behind the kitchen, a robust pantry borrows space from the former primary suite and houses the small appliances that can quickly clutter a kitchen. “On one wall is a 12-foot-high-by-15-foot-wide map of the community,” Colleen says. “When neighborhood friends come over, they can locate their house on the map.” 

For ease of indoor-outdoor entertaining, a new glass slider opens the existing bar area, in a niche on the house’s southwest corner, to a new covered porch and the front deck. And the old primary suite behind the kitchen was transformed into a mudroom, bath, and office opening to the back deck. “In some ways, I think of the house as almost a series of train cars with their doors flung open,” Colleen says. “You get this porosity throughout. From certain views you can see right through it, bringing in the community.”

But it’s the lofted primary bedroom that commands the best views. Within the footprint of the two-car garage below, the architect designed a double-height bedroom and sitting area, a bath, and his-and-hers closets. A curving wall with a pocket door at the top of the stairs directs you to a sitting area, creating privacy for the bed and eliminating the need for a hallway. Large windows overlook the front and back yards. Three more bedrooms are located one story below the living level, and the ground floor houses a gym, fifth bedroom, and play space that spill out to backyard. 

Character Study

“This is a fairly rural area, and parts of the house reflect the funky neighborhood, sort of campy,” Colleen says. “The owners wanted to retain some of that but with a modern touch.”

  Throughout, industrial accents nudge the rustic-leaning themes—such as the antlers in the bar, the wood-burning fireplace, and the dark iron dining table and chairs—into modern territory. Punches of black from the light fixtures, bar shelving, range hood, kitchen cabinets, fireplace surround, and stair rails tie into modern touches such as the sleek porcelain floor and wall tile. The firm also designed the living room coffee table, whose COR-TEN frame, made by a local fabricator, matches the façade’s COR-TEN cladding, reinforcing the industrial vibe.

“The COR-TEN was a decision that ended up being very economical,” Colleen says. “We wanted something to contrast texturally with the cedar and ground the building, especially since the panels are more sunken into the ground. As the two materials weather, one will get darker and one will get lighter.”

However, because the project coincided with the end of the pandemic, the COR-TEN budget was complicated by supply issues. “In essence it’s a commodity product and not overly expensive, but it weighs a ton; trying to navigate all the materials on time and within budget was one of the unique challenges,” says builder Josh Rosenthal. “On a jobsite that’s basically a steep hill, we couldn’t get things in advance and stack them up. But it was our favorite kind of highly customized project with a lot of solutions to reinvent.” 

Balancing old and new, the design has transformed daily household routines while honoring parts of the house’s past. The usable front yard is just one of those feel-good spaces. “They’ve talked about dropping a projector to show movies in that area,” Colleen says. Open from front to back, the house reflects the family’s vision for a good home life. 

COR-TEN Tree House

Bethesda, Maryland

Architect: Colleen Healey, AIA, Colleen Healey Architecture, Washington, D.C.

Builder: Josh and Neal Rosenthal, Cabin John Builders, Cabin John, Maryland

Structural engineer: Norton Engineering Consultants, Fairfield,
New Jersey

Project size: 3,600 square feet

Site size: 17,000 square feet

Construction cost: Withheld

Photography: Jennifer Hughes Photography

Key Products

Cabinetry: Stuart Kitchens

Cabinetry hardware: Top Knobs

Cladding: COR-TEN steel, cedar shakes, JamesHardie panels

Cooktop: Miele

Cooking vent hood: Miele

Countertop: Caesarstone

Entry doors: Western Window Systems

Fasteners: Simpson Strong-Tie

Garage doors: Clopay

HVAC: Carrier heat pump

Skylights: VELUX

Thermal and moisture barriers: Henry Blueskin

Underlayment, sheathing:
ZIP System

Vanities: Stuart Kitchens

Ventilation: Panasonic

Windows: Pella Windows & Doors

Window wall systems: Western Window Systems