La Casa en Guanajuato

30 September 2006 - Arches

Another entry on construction techniques, this one on arches. Unlike the boveda ceilings, which are build free standing, arches are built by building a falsework, a 'mold' or negative of the arch. The arch is then constructed supported by the falsework. Once the arch is in place, locked with the keystone, the falsework is removed, leaving the completed freestanding arch.

I watched a show, "Modern Marvels", on the construction of the Pacific Coast Highway. The graceful concrete arches which soar hundreds of feet were first framed out with timber falsework.

Every arch in the house (and I haven't counted, there are lots) was constructed with this same technique.

So why doesn't the boveda ceiling require a falsework? Because each course of bricks creates a ring, which much like a manhole cover, is unable to fall through the hole. If the mortar is tacky enough to support the weight of the one brick, the course can be completed, and once completed can easily support the weight of the next course. I wasn't there when this ceiling was built, but I understand it was completed in 2 days.