The Deep Dive: A Thick Skin

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.

If bark is strong enough to clad a tree for several hundred years, then why not use it to envelop a house? So Andrew Linn and Jack Becker wondered as they brainstormed exterior claddings for the Capital Building featured in Dwell’s January/February issue. (Linn and Becker founded the Washington, D.C.–based firm Bldus that’s behind the project.) Today, poplar bark wraps the second floor of the alley residence, which Linn occupies with his wife, Hannah, and their young son.

What might strike the casual observer as an aesthetic choice was, to Linn and Becker, a practical means of achieving a nontoxic, high-performing residence that has the same longevity as one of Washington, D.C.’s institutional structures. The Appalachian poplar bark that the architects sourced from Bark House in Spruce Pine, North Carolina, earned the first Platinum-level Cradle to Cradle certification in 2016. Equally important, the shingles can endure at least 80 years after kiln drying without sealants or treatments.

At Bark House, fabricating poplar bark panels begins with peeling. Once a log is felled, its trunk is scored in a ring by chainsaw. The tool is then run over the length of the log, after which bark is stripped by hand employing so-called barking spuds. Sometimes one of the resulting proto-panels snaps before it can travel down the mountainside for processing. Other times, the panels break during the descent. Yet even in less-than-ideal cases, the finished material holds more carbon than the carbon emitted to harvest, refine, and transport it. Compared to traditional felling that treats bark like waste, the process also increases the income for Appalachian loggers.

In the hands of Bldus, the poplar bark shingles establish a vocabulary for a building type with little surviving precedent. Although approximately 20,000 Washingtonians lived in the capital city’s alleys through the early 20th century, President Roosevelt’s 1934 signing of the District of Columbia Alley Dwelling Act funded widespread demolition as well as limited rehousing efforts. The initiative cleared the alleys of these dwellings, sparing some masonry structures along the way.

In addition to the poplar bark cladding, Bldus sheathed the home in cork around its ground floor. On the building’s east elevation, a sassafras fence with black locust framing merges with the house, taking the place of the cork. The eaves supporting the roof are punctuated by black locust, and the lumber of this historically strong, rot-resistant tree also frames the porch. Topped by a low-angled pyramidal hipped roof that culminates in a gridded skylight, Bldus’s palette neither recreates a lost local narrative, resembles extant alleyway buildings, nor repeats the domestic motifs of historic streetfront homes.

The composition not only signals an updated definition of the Washington, D.C., alley house, but also the performance of the residence overall. Underneath the nature-made skin stands the East Coast’s first structural frame made of bamboo (which, Linn explains, has a smaller carbon footprint than mass timber in spite of its shipment from overseas), while the home also boasts wool insulation, energy-sipping equipment, and milk-paint interior surfaces. Just as poplar bark is a healthy resource for the design and construction marketplace, the Linns’ new home is an alternative to current mainstream housing that will repay its ecological debts over a long life.

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