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2005 Cast in place concrete, 316L stainless steel
Site: existing house on Tampa Bay
Challenge: design a new stair that marks entry clearly while offering a focal point & inviting access to the living level. Also a railing was needed around the second floor balcony/walkway. This was to be as maintenance-free as possible and feel light and elegant.
Obstacles for stair: limited time--could not be on site every day. V-zone requirements--structure must resist crashing wave forces, erosion & wind of 100 year storm.
The stair cantilevers up out of the ground and does not touch the house structure above, but leaves a 3/4" reveal. This adds to its elegance and prevents water intrusion damage over time from a connection to the frame & stucco structure of the bridge above.
Solution to the construction process is that the concrete forms were built by Robert Berg of Berg Quality Craftsmen, and his crew of really talented guys. They were, at the time being the owner's crew of "painters" who are actually excellent craftsmen. I produced drawings that were essentially 3-dimensional assembly diagrams, with each piece detailed to shop drawing level. I laid out the curves on site with them & they did the rest for the most part with fairly frequent site drop-ins.
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Above: Original Cad model rendering showing the cantilevered system and the foundation connection to the existing grade beams & pilings.
Right: stair in 2016 March, after re-finishing the concrete.
Below: Initial sketch , ink on trace, pencil
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Right: 2016, just after the resurfacing (see below for description).
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Above: initial sketch , ink on trace
Right: stair in 2016 March, after re-finishing the concrete.
Below: Original Cad model rendering showing the foundation connection to the existing grade beams & pilings.
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2016 - There had developed some surface cracks on some of the treads and the lower steps. Some were fairly wide and were letting water into the system which would eventually become dangerous to the steel since not all of it was epoxy-coated. The cause was likely too high a water:cement ratio at the initial pour as the cracks (although small) appeared not long after the forms were stripped. The cement shrunk too much as it cured. At left also can be seen some staining after 10 or so years of water running off the galvalume roof onto it, bringing trace metals, water, and oxygen with it which reacts with the cement in the stair and stains it. The solution was to wire-brush the surface to remove any loose, degraded concrete, wash it down and then apply a thin coat of SikaTop123Plus which is a two part, polymer modified portland cemtent mortar which has an anti-corrosion agent in it that seeps into the concrete up to 1.5" and chemically attaches itself to the rebar to protect it from corrosion. The coating is applied like stucco and trowel finished smooth. The entire stair was then sealed with an LM Scofield Chemtone clear sealer which will keep a natural, mate finish, but will provide additional water intrusion protection for the surface.
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