Andrea Cochran: Landscapes (Princeton Architectural Press) is a book I often pull off the shelf for design inspiration. Sized to hold comfortably in your hands and made with heavy paper, it showcases 11 residential, institutional, and commercial projects, accompanied by an appendix of scaled plans and plant and material lists. Mary Myers’s observant narrative nicely illuminates the ideas behind the projects.

I recently had a chance to ask Cochran about a particularly moving aspect of her work: the use of quiet gravel planes to create sculptural, dream-like geometric spaces. Think large gnarled trees rising from flat swaths of gravel; undulating strips of succulents paired with thin metal edging and river rock; and a pale crushed-stoned courtyard bordered by staggered rows of horsetails with crew-cut tops. Soft, crisp, crunchy, plain, shapely—there’s much here to delight the senses. (For more of the firm’s work, go here.) In an interview, Cochran shared her thoughts about gravel—an environmentally friendly and relatively inexpensive paving alternative.

Why are you drawn to gravel?
There’s something really magical about gravel. It changes—it looks different wet than dry and reflects light in different ways, so you can cover a huge area with it. I like things that are really simple and pared down to the minimum, but not cold. Gravel has some warmth, and it makes a noise when you walk on it, so it has a sensual aspect. We did a hotel in the Sonoma wine country with a courtyard where guests are dropped off. Someone said they loved going there because when they stepped out of the car, they landed on this crunchy decomposed granite with a light gravel coating. It was a release, and told them they weren’t in the city anymore.

As a designer, you modulate how someone walks to influence how they experience the space. There’s something psychologically grounding about hearing sound that we don’t think about when we’re walking. It’s a Zen kind of thing that centers you and makes you less stressed.

What types of gravel do you use?
In California, a lot of it is granite. Hard, cool granite comes from the Sierras; other projects use gray to tan to pinkish coastal granite that’s pulverized to different degrees of coarseness. Pea gravel is more alluvial. We try to use indigenous materials so their colors work with our environments.

For the north side of one residence, we selected gravel with light, cool tones, which went with the architecture and brightened the shade. At another, we picked one that was warm and not too bright in the sun. I try to choose gravel that doesn’t have a huge color variation—that has some life in the way it reflects light, but reads as a uniform plane. Too much white mixed in destroys the overall unity.

How do you install it?
Pedestrian areas usually have 4 inches of compacted base rock topped by ½-inch of gravel. At Walden Studios, we used gravel inset with small rings to make it ADA-compliant. Off-the-shelf thin steel edges, 4 inches deep, hold the gravel in place. Sometimes we use aluminum edging in certain areas if there’s a limited budget.

What about maintenance and performance?
We mitigate tracked gravel by placing it at a distance from the house so you can walk it off, or select larger gravel that doesn’t fit into the waffle bottom of shoes. Sometimes we’ll use a grill between the gravel bed and the door to catch stray pebbles. We also choose interior floor surfaces that aren’t easily damaged. Decomposed granite, in particular, is compacted, so you do track the fines, and they’re really abrasive. I’ve had people rip out gravel because they didn’t like what it did to their floors, and I try to be upfront about that downside. I have a gravel courtyard and sometimes get a few pebbles inside, but for me it’s worth the trouble. To keep it tidy, you rake it a bit, or use a leaf blower.

Another reason I like gravel is because it’s permeable, and it’s easy to repair over time, compared to a hard surface. You can bring these planes up to a tree—like the Tuileries gardens in Paris. If you do that in concrete, you end up with rings around everything.