The Deep Dive: An Evocative Exterior

A onetime candy factory gets a sweet transformation thanks to an all-black exterior palette.
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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.

Of the factory-turned residence in Cambridge, Massachusetts, featured in the November/December issue, author Kelly Vencill Sanchez writes, "The building’s eccentric past wasn’t what drew Paula Chauncey to buy it in 2011." Yet the building’s previous chapters—originally as a candy making facility, and more recently as a headquarters of the startup investor Y Combinator—didn’t dissuade Chauncey from purchasing it, either.

"While Paula certainly appreciates an industrial aesthetic, during this project itclicked for me that she’s a storyteller and she wanted the house to tell a story, too," says architect Sandra Jahnes, who oversaw the building’s transformation with longtime collaborator William Ruhl. "She certainly didn’t want this renovation to erase history," Jahnes says. Ruhl and Jahnes, who now practice as the Watertown, Massachusett–based studio Ruhl | Jahnes used this realization to guide the material and finish selections for the building’s exterior.

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Thanks to that postponement, she and Ruhl introduced Paula to shou sugi ban, the ancient Japanese technique of preserving exterior wood via charring. "We’ve been fans of shou sugi ban for some time, even though none of our clients had taken the bait yet," Jahnes says. Paula, on the other hand, jumped at the possibility of using it as cladding because, as Ruhl explains, "Paula loved the deep heritage behind the process, not to mention that the finished product keeps the water out and is maintenance-free."

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Ruhl | Jahnes sourced the exterior wood from Resawn Timber’s line of Kebonywood, in a colorway that Ruhl describes as "an intense black that is almost blue when the light hits it, like a crow." He and Jahnes paired it with a similarly colored Zalmag, "because it has some natural patina, and Sandra and I both like its imperfections. Inherently it looks like it has age." 

Now that the two black hues had been locked in, it was time to revisit the cement block. With Paula resetting her vision to a midnight finish, the team thought that a matte black paint would complement the surfaces overhead. Embracing an all-black palette also could turn the threshold-crossing experience into a dramatic statement. "It promised to be foreboding from the street, but once you get inside it would feel like a nest basking in sunlight," Ruhl explains. "A lot of our houses tend to minimize the distinction between inside and out, but in this case the distinction was very intentional."

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Yet the matte paint didn’t quite work, as it lacked the dimensionality or character of the Resawn wood and the Zalmag coated steel. In response, the team looked to ancient finishing techniques again. This time the Roman process of diluting and adding pigment to crushed limestone, or lime wash, presented itself as the best candidate. The coating would have to be applied in several layers, and because it is also porous, it would reveal the layers and undertones with time.

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On paper, the multidimensional quality of lime wash couldn’t sound moreperfect. The execution was more of a slog. As Jahnes recalls, test swatches were painted on the exterior on multiple elevations: "It was six of this base layer and six of that base layer, and the same top coat—all those combinations were incorporated into a grid. Anything that had warmth in it ended up looking murky and mossy against the Zalmag. The shou sugi ban also has that bluish tint to it. In the end we had more of a battleship gray base layer with something dark on top. Getting that tonality right was challenging."

But also worth it. Besides Paula’s own satisfaction with the finish product, new and potential clients of Ruhl | Jahnes "appreciate the lengths we went to make it her house," Ruhl says. The Cambridge Historical Commission even joined the chorus of voices. During its online presentation of the 2022 Cambridge Preservation Awards, the group’s executive director Charles Sullivan lauded the project for transforming the onetime candy factory without obscuring the original cement block—nor the many lives the building had lived prior to Paula’s arrival.

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