He knew he had to have this Runnels home 12 years ago. Now, does he stay or go?

Tom Smith had an intuition about his future when he saw an ad for a house in the Kansas City Business Journal.

“I pretty much knew then,” he recalls of that moment 12 years ago. “It looked very interesting, and I was excited before I got here.”

He pulled up to the house in Wycklow, a hidden gem of a neighborhood poised inconspicuously near the busy intersection of 103rd and Roe in Leawood.

“This heavy gate closed behind me like this medieval door, and I saw the pool,” he says. “I thought, ‘Yup, I’m home.’”

The reason he liked the house isn’t much of a mystery. It was designed by famed local architect David Runnels, known for his mid-century modern designs.

“It was built in 1966, which surprises people,” Smith says. “These designs don’t age; they’re timeless.”

At the time of his purchase in 2006, he was divorced and looking to downsize. His grown kids said, “It’s so you, dad.”

As the owner of Gold Crown Properties, which recently refurbished the historic Pickwick Plaza, Smith knows something about preserving and restoring architecturally significant structures.

“I wanted to be an architect when I grew up,” he says. “It’s a long story why I didn’t, but this house is how I satisfy that craving.”

He appreciates the home’s major points of interest, including a cathedral-style window wall in the main living space and narrow Plexiglass inserts in the stairwell. The interiors feature cut redwood paneling, which is no longer produced.

“In addition to being an architecturally significant house, what’s important to me is where it sits,” Smith says. “It’s wonderful to have this right here in the city yet be completely private.”

The house is built into the landscape, settled back into a cul-de-sac among mature trees and shrubs. Down below, Indian Creek trickles around a bend behind the house, with views of nature in all directions.

However, its lofty position was almost its downfall. The house’s infrastructure has had to undergo extensive renovations to secure it in place.

In the 1980s, it was discovered to be gradually slipping down the hill. A former homeowner spent $600,000 to bore 66 piers into the bedrock to save the house.

There have been many other updates from different owners, altering various spaces while preserving the architect’s original intent. Changes include the installation of an infinity pool; upgrading all the windows to double pane; doubling the garage by making it tandem and refinishing the kitchen in cherry cabinetry.

“Over the years, the house has had a fortune spent on it,” Smith says. “A contractor today couldn’t touch this for $2.5 million.”

For all its updates, the interiors have a vintage vibe, from the Bang & Olufsen CD and tape deck hardwired throughout the house to the master bath’s decades-old brass and blush, which are back in style today.

The labyrinth-like floor plan has not been altered, with a few exceptions. Smith’s favorite addition is the stone-foundation greenhouse with live ferns and a wood-burning stove. He says the space has been used for several purposes, including dining room and yoga studio, before it was his man cave.

“To me, I love the warmth of the wood, stone and glass of this room,” he says.

Smith made a minor addition of his own by creating a mini kitchen in a former balcony off the master bedroom. But he’s considering something bigger.

He and his wife, Mary, whom he married in June, have had plans drawn up for a new wing on the house that will emulate the original architecture while giving them the space they need to host their combined families.

Because the house has only two bedrooms, the addition would include a spacious master suite on the upper level plus more rooms beneath, including a sewing room for Mary.

“I’ve loved the house since I met Tom 11 years ago, but I haven’t lived here yet,” says Mary, who will add a few feminine touches with heirloom pieces and quilts.

“It’s hard because I’m moving into a house that’s already furnished,” she adds.

Many of her belongings have gone up to the couple’s Lake Viking home, where they spend weekends. In fact, that house might be the full-time future for the newlyweds, who are at a juncture. Do they move forward with the addition or leave the beloved Runnels house behind and retire to the lake?

Only time — and maybe this story, like the ad Smith came across that inspired him so many years ago — will determine the next phase of this house’s history. Whatever that may be, he wants to see the house evolve in a conscious way that maintains the integrity of the design.

“When you stand down in the yard and look back at the house, it’s just beautiful,” he says.