To say that Keri Petersen has a knack for stylish bargain hunting as part of her design process would be a gross understatement. Point to nearly any furnishing in the interior designer’s new home and you’re in for sticker shock of the positive kind. Glam champagne-hued entry pendant? $69 from Home Depot. Retro-chic cane armchair? $34 from Goodwill. Mod molded-plastic dinette chairs? $20 each from Craigslist.

“My husband’s a middle school art teacher, and I own my own business. So we’re not rolling in it,” Petersen says. “I’m always trying to stretch my budget.” Aside from necessary penny-pinching, however, it’s a love of retro design that has made the Bellingham native an expert at trolling secondhand shops (one of her favorite local go-to spots is Ballard’s Goodwill store) and online sites eBay, Craigslist and Etsy. So when she and her husband, Justin, and their two young children, Maggie and Jude, moved from a cramped 1924 Ballard bungalow last year into a nearly frozen-in-time 1952 brick dwelling in Seattle’s Blue Ridge neighborhood, Petersen was well-prepared to take on the era-appropriate remake.

While the home’s original white shag is no more, replaced with warmly striped hardwood, vintage furnishings still hold sway, including a pair of 1950s powder-blue armchairs ($200, Craigslist). Designer Keri Petersen says midcentury modern furniture’s low price point and durability make it kid-friendly.

“It was so dated,” she recalls. “The house was covered in white shag carpet original to the 1952 layout, there were heavy drapes covering all the windows, and everything was kind of dingy.” But the house did strike a happy childhood chord. “My grandmother had a midcentury house with a shag carpet. We would have to brush the shag at night with our hands to make it perfect,” says Petersen with a smile. “And it just kind of clicked that this house could be a really cool thing.” The open, optimistic nature of the home’s midcentury modern style also suited the young family. “I wanted to make this space so happy and so cheerful, [but] I wanted something solid and stable,” Petersen says. “I wanted a forever home.”

Knowing when to say “no” is a big part of Petersen’s general approach to design, and it can be a room-saving skill when it comes to retro looks, which have a tendency toward kitsch overkill. While one garden gnome is cute, she advises, 100 gnomes are disturbing. “Restraint is definitely built in here, as is balance,” she explains. And while her home’s 1950s swank—from clever built-ins to the kitchen’s original Sears stove (bearing temp options like “vigorous boil”)—is lovingly in evidence, so is a brisk 21st-century sensibility.

Right: Keri underscored the brightness of the space by spray-painting vintage black dinette chairs ($20 each on Craigslist) a perky mint green and adding a spiky gold Urchin pendant light ($399) from the Etsy shop Stimulight (etsy.com).; Left: The kitchen remains almost unchanged, including its cabinetry and original Sears stove

The white shag carpet gave way to warmly striped hardwood, and the home’s largest spaces, the dining and living rooms, were given modern, brilliant white walls, against which Petersen unleashed some splashes of vivid color, such as a large painting of crashing aqua surf in the dining room, and funky flourishes, such as a set of golden seahorse table lamps in the entry. “In Seattle, we can get a little drab, and I think people have more memorable moments in a house that has color,” she says. “My clients are asking for color and pattern in big ways, and they are not afraid to take those risks, and I’m right there ready to jump with them.” (Petersen also is a cunning real estate stager.)

The designer’s eclectic furniture is a lesson in artful blending—a new midcentury-modern-style vibrant pink couch from Urban Outfitters sits next to a Craigslist-sourced pair of 1950s powder blue armchairs—and is aptly minimal. “It’s like putting together a puzzle. You just kind of know what fits,” Petersen says.

Clockwise from left: A pair of seahorse lamps flank the home’s entry; A deep, metal-lined box, one of many original built-ins, tops a dining room cabinet. Come party time, it’s packed with ice and libations; Interior designer Keri Petersen with children Jude and Maggie at a vintage Lippa fiberglass pedestal table with marble top ($769, snagged on LexMod.com).

And while this interior designer considers her own home a work in progress (she is constantly changing out its accessories and art), as of now, she says, “This place makes me really happy.”