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Monday, May 28, 2012

One "very cool" unique stairway - Part 1: design

One "very cool" unique stairway

   While doing a skills training course overseas, a local businessman approached me about designing and building a staircase for his mountainside office retreat.  His only requirement was that it must be an original "never seen before" design.  How could I pass up a chance like that - of course I accepted.
  The building being constructed as his mountainside office was a two-story concrete block hexagon with approx 15' sides (everything was in metric, of course).  The front side of the hexagon faced out over the hillside and took in an incredible 270 degree view.  The lower level had a set of French double doors that opened onto to a large patio with a deck that overhung a steep fall-off grade.  Located inside along the back wall (opposite the doorway and patio) was a long, thin, single story bathroom with a flat shelf type ceiling when viewed from the loft above.  The upstairs level was nothing more than a gently curving loft style floor having a small "standing room only" balcony extending out a set of French double doors over the patio below.  The loft covered slightly more than half of the lower floor's footprint and was located just under 9' above the first floor.  The floor joists defining the loft hung off the front wall (or the wall with the double patio doors) and cantilevered over a steel beam run down the middle of the building from side to side.   There were no interior walls, no stairs yet (of course) and the building was open two stories to the roof rafters.  It had a very nice airy feeling inside and a view from just about any position inside except the bathroom.  The downstairs was to have a centrally located pool table with a small entertainment/living room area off to one side and the stairs set off to the other side.  The upstairs loft was the office.  The placement of the bathroom door on the back wall limited the placement of the stairs so there was only about 8' of horizontal space available to ascend 9' vertically.  I could definitely see the challenge of building a normal staircase within the space available given the need to keep the center clear for the pool table.  The architect had figured only  a ladder-type or spiral staircase would work.  Neither was acceptable to the owner
  After a little brainstorming, I suggested we convert the dead space over the bathroom to a separate library space with built-in shelves and connect it to the office loft by means of a centrally located front to back "step-up" bridge (versus a bridge built to be flush with the loft floor).  From the loft end of this bridge, the staircase would descend towards the side wall which was opposite the fireplace (where the architect had originally planned his ladder or spiral design staircase) and then hook around to the right to terminate at the bathroom door (door would swing in).  The staircase would be shaped like a reverse question mark (?).  In keeping with the radius type theme of the loft, the bridge would have a gentle hourglass shape and the stairs would follow/match the curving front edge of the loft until near the outside wall were they would reverse and begin an ever tightening nautilus type curve to the the right.

Design sketch

  Not only would the stairs be irregularly curving in structure but I also designed the treads and risers themselves to be curved and progressively changing from a gentle curve with a long radius at the bridge to a much tighter curve with a short radius at the very bottom step.  Compounding this, I would support more than half the stairs by straight-run stringers to keep the the center of the lower floor area free of obstacles for the pool table.  Having the bridge as a "step-up" design helped increase the headroom below the straight run section of the stairs until they were much closer to the side wall  The first 7 risers in the lightly wound bottom section located against the buildings exterior walls would be built using a combination of short 2x4 walls and 2x12/2x4 riser assemblies as shown on pgs 276-277 in the 2002 version of "A Roof Cutter's Secrets" (RCS).  The more gently curving upper 9 treads would be supported by three regular 2x12 stringers.  A half arch would serve as the transition from wall style stair construction to the notched stringer style construction.  I would frame the structure using straight lines for the treads and risers, while a cabinet shop would build the finished treads and risers and apply them as an overlay.  The curved lower support walls, the arch and the stringer assembly would be finished with plaster to create a contrast to show off the magnificent tropical hardwood top surface.

Continued in Part 2: layout and construction

Copyright 2008 by Will Holladay