[All images by BUILD LLC]
BUILD recently completed the CSH2017 in the Ballard neighborhood of Seattle. It’s the latest in the Case Study House series and, like the others, it improves on the model, tweaks some design components, and experiments with others. The grade sits a full 14 feet above the street, while the hillside slopes parallel to the street. In order to produce an efficient and usable residence, the design process focused heavily on the stair design strategy, both inside and out. Today’s post reviews the vertical circulation of the structure from bottom to top.
In order to navigate from the sidewalk to the front door, two types of stairs were implemented. A cast-in-place, concrete slab on grade stair ascends to the top of the hill and is lit at every fourth step by a recessed tread mount exterior grade light by Vista. Because the height between the top of the stairs and the adjacent grade is always less than 30 inches, a guardrail isn’t required but a handrail is (IRC 311.7.8 if you want to get nerdy). In this case, we use a slender galvanized steel rectangular cross section that attaches to the side of the concrete stair and extends up 36 inches. From the top of grade to the main floor entry, a wood framed stair is wrapped in ipe, a hardwood known for its resilience, while the galvanized handrail geometry is outfitted with horizontal steel rods every 3-1/2” to double-act as a guardrail.
Once inside, the interior circulation stacks in order to consume as little square footage as possible. A solid stair leads to the lower level, while an open riser stair extends to the common areas of the upper floor. At the upper stair, 3/8” thick steel plates extend from blocking at the wall to a blackened steel channel at the open side. A blackened steel guardrail attaches to the channel while the handrail is located at the wall side to keep the guardrail uncluttered. Solid oak boards then wrap the steel plates creating a series of monolithic treads. All interior stairs are solid oak with an ebonized stain to match the hardwood floors.
To best optimize the view and natural light, the residence uses the inverted floor plan and the attenuated steel stair minimizes obstructions at the common space. A thin steel guardrail encompasses the stair opening from below while a set of blackened steel channels reaches to the roof hatch above. A roof deck less than 200 square feet in areas doesn’t require a code compliant stair, and subsequently there are fewer limitations around the rise and run of the treads as well as the guardrails and handrails. With minimal obstruction, the roof stair delivers inhabitants and visitors to a sweeping view of Ballard, the Olympic Mountains, and Seattle beyond.
One of the important design intents of the CSH2017 was to create a series of experiences with smart, crafted stairs that make navigating the house a pleasure. The nearly 40 vertical feet of stairs in this project do their job effectively without getting in the way of the experience or the views.
Cheers from team BUILD