This is the fourth project by Caro Robertson and Tim Gittos, of Spacecraft Architects, that I’ve written about in these pages. There was Sidecar, an extension to a house up north; Block Party, a co-housing scheme in Te Whanganui-a-Tara; and Full Frontage (or 108 Aro St), a three-storey house nestled among older buildings in Aro Valley. With this design, Terraced Plot, a two-bedroom home on a very steep site in Wellington’s Brooklyn, I think I can just say at the start what I’ve danced around before, which is this: in print or online, Spacecraft’s houses can look surprisingly simple and functional. Things are modest. And yet that modesty – a determined simplicity – is by design, rather than a result of necessarily constrained budgets.

Here’s an example of what I’m trying to say. You’d expect that, if given the chance, architects might specify higher-quality products for their homes – some Arne Jacobsen tapware, say. It would likely be nicer to use, and is unquestionably beautiful. (Wouldn’t mind some myself.) But when speaking with Brett Miller, who owns this house with his wife Michelle, things were reversed. “Tim asked me one day, when we were discussing taps, ‘Brett, do you really want to be the guy with the fancy taps? Do you need that?’”

Approaching this house, you have the same sense of things being reduced to essentials. From a carport just off a very windy street on a hillside, you take a long flight of stairs down to the house, approaching it obliquely. And there’s really nothing to see: just a single tin box, with a chimney popping up above the roofline. The valley spreads out beyond, and the house looks very small, very modest, very nondescript.

At the bottom of the stairs, you turn left to the front door. Entering is a surprise: you’re thrown into a much larger space than expected, with slices of the valley now framed and emphasised, including an old pōhutukawa seen through a vertical window in the kitchen down one flight of steps. To the left of the front door is a room with bench space and a sink, used by Michelle for craft; beyond that is a door leading to a vegetable garden on the side of the house. To the right of the front door is the staircase leading up to the two bedrooms; further to the right are the toilet and bathroom. Straight ahead, down one level, are the kitchen and dining areas, with another courtyard at left. Down one more level is the living space, a snug area with a fireplace, bookshelves and another deck. All of this opens up in front of you in an instant, and the inaccessible, steep site suddenly welcomes you to move down and across it.

“There’s lots of spatial complexity for just a little place,” Gittos says. “In some ways it was like a formal playground with the views and the level changes. So you’ve got three boxes down the hill: one two-storey, one one-and-a-half-storey, and another one-storey. The first is in the ground, the second is on the ground, and the third is above the ground.” These forms are all visible from inside the front door, and you’re led through them via internal stairs that expand and contract to at times form bench seats. It all feels very natural and relaxed. The forms also appear to slip past each other slightly as they move down the hill, with the volumes reducing in size. This makes for unique views as you simultaneously look outside and into the form below you.