For siding, Gracia likes to go natural. His preference is California redwood, which he calls “one of nature's most maintenance-free building materials.” According to the California Redwood Association, the species accepts finishes well because of its open-celled structure and naturally resists shrinking, warping, and checking. It's also resistant to decay and insects. Dark-stained redwood is shown here on the architect's own home in Mexico. California Redwood Association, 888.225.7339; www.calredwood.org.