Promontory Office Center

Type: Commercial Office

Building Method: Wood stud and stucco on Concrete caissons

Location: San Luis Obispo, CA

The Promontory Office Center Complex in San Luis Obispo, CA. is a very unique design for a very difficult, triangular site with lousy soil conditions located on a steep slope between a running creek on the one side and the 101 Freeway on the other. The first problem was getting over the creek without disturbing the environment of the creek bank with excessive construction operations. The solution was to purchase a railway flatcar that was modified into a bridge deck and then set over the creek in one fell swoop. This method only required minimal work on the creek banks to install the caisson supports for each end of the railroad flat car. The problem of the lousy soil on site was to install drilled concrete friction caissons since bedrock was too deep to allow an end bearing caisson. The other problem is that many of the caissons had to be drilled on the steep slopes over the creek. Special hillside drilling rigs were brought in that were anchored at the top of the bank and then lowered down by winch and cable to the caisson location where the drilling was happening. Once the caissons were installed and the foundation complete then the remainder of the construction was very typical wood frame construction with pre-engineered wood truss floor structures, wood studs with sheetrock on the inside and cedar shingles on the outside and stud cavities filled with insulation. Roof structures were framed and trusses with cedar shingle roofing. Due to the slope of the site there were pedestrian bridges built between some of the buildings on the site. Parking was placed on the level areas of the site so grading could be minimized.