FLOATING CONCRETE: Stairway at House 7

House 7 Stairs | Sideview | CHENG Design | sustainable, emotional, timeless design

I’m standing in the foyer lobby of the house [House 7]. Finally, here, I was able to utilize all these different experiences of working with finished concrete in a super-engineered sculptural way in this staircase. For myself, being so involved with concrete for so long, for so many years, this is the pièce de résistance of sculpture and function all coming together in one fell swoop.

House 7 Stairs | Sketch from above | CHENG Design | sustainable, emotional, timeless design

House 7 Stairs | Looking up | CHENG Design | sustainable, emotional, timeless design

Each one of these treads weighs approximately 250 pounds. They were “sledded” in on tracks. The guys moved each tread and slid it on so that the tongue that is only 5 inches square would connect to the wall and we could cinch up the strong steel members that go through the staircases and then are tightened by these acorn bolts right there. So, these stair treads are held in tension and to do a test to see the efficacy of the engineering, the engineer and I came down here and I let him go first! So, he stood on these and we put a 600-pound weight and I jumped on! The two us—engineer, designer—and 600 pounds, and these deflected only 1/8 of an inch! This is the dramatic piece that is cantilevered out from the wall in just that small connection there, so it has this magic of floating.

House 7 Stairs | Sketch looking up | CHENG Design | sustainable, emotional, timeless design

Coming down to the basement level, a lot of light comes in here. These staircases we cast in our shop just like the others, but they are not cantilevered. They are sitting on top of a rough staircase. These are sort of like dental implants put over a roof. You can see the staircase that comes down is really isolated to the center. I put these two rails and put some exposed aggregate on both sides of the staircase so that it further emphasizes the sculptural nature of these stair treads. I took a bevel out of each face just at the same angle as the angle that is in the cantilevered staircase that is going up.

House 7 Stairs | Sketch from the side | CHENG Design | sustainable, emotional, timeless design

At the bottom of the stairs, you’re going to have an exposed side which is sheared off here. Wanting to keep a sculptural nature brought out a little elevation change so one part is flush, one part is sticking out—further emphasizing this angle cut in the face of the staircase. Then you see these cables which are pretty taut. This is almost a harpsichord-like tension here. And, these are every four inches apart to code so it acts as a guard rail but really lets the light come through from the windows to the outside. I’m in the full basement right now being bathed in light essentially.

House 7 Stairs | Sideview | CHENG Design | sustainable, emotional, timeless design

-Fu-Tung Cheng

See related article on Concrete Network: Making Cantilevered Concrete Stairs Look Weightless.