Originally built in 1997, the Belvedere-Tiburon Library enriches the local community through its halls of knowledge and community events. More recently, the single-story library was expanded, adding 8,600-SF of space for children and teens libraries, an art gallery, founders room, makerspace, computer learning classroom and conference rooms. The expansion also added Corner Books, a used bookstore that was previously located next to the library, administrative space and a large community room for meetings and guest lectures. Miyamoto prepared the structural design for this expansion. The structural system is composed of light-wood-framed shear and bearing walls and heavy timber roof trusses. While developing the design for this expansion, our engineers faced two challenges. One was to hard-connect the addition to the existing building and the resulting seismic evaluation and retrofit. The other, and probably most noteworthy of the two, was the soil. The area is infamous for its bay mud soil conditions: buildings built there are very vulnerable to settlement. Our strategy was to build a partial height concrete-framed basement; in turn, the soil that was removed for that basement would offset the new building weight.