The Deep Dive: A Sunken Treasure

As any issue of Dwell proves, the choice of material or joinery method can transform a good project into a design for the ages. The Deep Dive is a forum where design and building pros can obsess over those details. Here we ask expert colleagues to share the inspiration behind house elements that delight clients—as well as the nitty-gritty information about how they were built.

The Toronto laneway house featured in "A Secret Garden Grows at the Heart of This Bunker-Like Art Studio" is a marvel of efficiency. Designed by Toronto-based Firma Architecture founder Lia Maston for her artist sister Sara, the building makes the most of every available setback and height regulation to measure 620 square feet. Perhaps more impressive is Maston’s approach to the "art bunker" in section, splitting it so that the basement, first, and second levels include both 7- and 12-foot ceilings—and making the interior feel large and discoverable. 

Maston says that the art bunker’s split-level configuration did not come immediately. Compared to earlier iterations of the design that featured full floors, she says, "what you get with the split level is a play of ceiling heights that’s like trompe l’oeil in terms of spaciousness, and which lets you see one level from the other." Sara was enthusiastic about the revised design’s treatment of volumes, and its accommodation of her work with tall canvases.

Maston’s vision includes a series of exterior destinations that correlate with each floor in the laneway house as a way of expressing those floors’ intricate layering. For the basement, Maston created a rectangular-plan sunken courtyard that connects to the interior’s 12-foot-tall portion via French doors topped by a generous transom. By creating this glass-separated adjacency, Maston says diffuse daylight "that’s good for making and displaying art" flows into Sara’s workspace.

To create footings, Maston’s team had to dig deeper than the frostline, which is measured in relation to exposed ground rather than the street. "There are strata that were excavated, including clay soil and ash," Maston says. The sunken courtyard’s walls were constructed like retaining walls and made of concrete block like the art bunker. "It was all done by the same mason, with him making the walls of the foundation and the courtyard together," she adds. While all the blocks have the same dimensions, the units sourced for the structure feature a glass aggregate.

In detailing the sunken courtyard, Maston considered water in addition to temperature, installing a pebble-filled drainage bed beneath the topsoil so that falling precipitation percolates into the ground. An off-the-shelf drain collects stormwater runoff from the first-floor level: Maston finished this upper area in exterior decking to transform it into another outdoor destination, and she threaded the drain through the deck’s pressure-treated lumber to point into the sunken courtyard. Rain and snowmelt from the surrounding lot cascades through the conduit and into a ceramic urn. "I wasn’t really thinking about the planning of that drain, and the way it happened, it feels really nice," Maston. Meanwhile, the second level’s corresponding outdoor space comprises a rooftop balcony accessed by an abstracted widow’s walk.

The urn turned water element is the centerpiece of a subterranean garden, on which Maston collaborated with landscape designer Cardy Lai. Flagstone from an Ontario quarry is embedded within the topsoil to trace a path around the urn and toward a seat suspended from the first-floor deck, where the pressure-treated lumber spans a corner of the courtyard’s retaining walls. A red dogwood is an organic counterpoint to the hanging seat’s verticality, while ferns provide groundcover and periwinkle softens the intersection between ground and wall. "This summer, it is more like a jungle," Maston says. "It’s lusher, it’s a bit deeper. You do lose sight of the flagstone arrangement now, but I’m happy for that to be really planted."

Maston’s happiness has to do with overall effect. "It doesn’t feel like you’re in a basement," the architect says of her sister’s studio, which is conveniently located behind their father’s balloon-frame home in Chinatown. "We’re really downtown in this building, but the garden is a secret. Nobody can see you, it’s very peaceful, and you have this deep sense of nature in the middle of the city."

We welcome your thoughts and illustrative projects. Reach out to pro@dwell.com.