141. When the foundations of a building, whether new work or an alteration, extend below the foundation walls of adjoining property, shoring, needling, and underpinning must be resorted to, in order to protect the walls of the existing structure.

The contractor is usually held responsible for the successful carrying out of this part of the work, and, consequently, there are in all the large cities firms or individuals who make a specialty of shoring and underpinning. The architect, however, should be familiar with the methods used, and should see that all due precautions are taken for safety, and that all the beams, shores, braces, and posts are sufficiently strong to safely carry the loads imposed on them.