Building on a Hillside
Just about anyone who has visited Laguna Beach has gazed in wonder at the gravity-defying structures clinging to the hillsides overlooking the town. “How is it possible they don’t just slide down?,” people ask (especially those East Coast visitors). You have to admit, some of those properties look more like they’re hanging from a rope than being built on a solid foundation. So what is it that keeps these homes from plummeting like giant toboggans? The answer: Caissons!
So just exactly what is a caisson and how are they best prepared? Since you asked, a caisson is basically a shaft in the soil that is drilled down to a solid footing – usually (hopefully) bedrock. The shaft is then filled with reinforced concrete. Hillside structures in Laguna Beach frequently require a large number of caissons to be installed in order for the structure to be considered earthquake-safe. I was recently involved in a land transaction where it would have required 72 caissons for a 2,700 square foot house to be built. Some of the caissons needed to be 60 feet deep before hitting bedrock. The cost of the caissons was so prohibitively high – just short of $1 million – it rendered the project economically unfeasible. Bummer for all parties involved. It’s all about the geology of the soil.
Here’s a look at a project currently under way that requires nine caissons (much better than 72!) for the foundation. The big machine you see here is drilling the holes that will reach bedrock. The holes will be filled with reinforced concrete and will eventually support the structure: basically a massive set of stilts upon which the house will rest.
There are dramatic properties around Laguna with intricate engineering reminiscent of massive erector sets. Steel girders cross this way and that, fastening to caissons for support. The home shown here is one I’ve marveled at and have wondered at the creativity of the designers who conceived this plan.
I’m an admirer of architects and a fan of engineers, and am grateful for the wondrous creations they envision and create. It makes our town so much more interesting and unique. Plus, the views that are afforded by these hill-clinging domiciles can be breath-taking. Looking up at the commanding hillsides covered with homes like so many grazing mountain goats, one has to be impressed with the brilliance of their creators. And to think if it weren’t for the invention of the lowly (pardon the pun) caisson, those homes couldn’t exist.
Just don’t ever think of serving one for dinner.