When Aidan Schreiner arrived in Ridgway, he saw a site with the outlines of one-story buildings, and was a self-described novice when it came to construction.

By the time he and the rest of his Americorps team left nine weeks later, the houses had second floors, garages and started to resemble three homes for Ridgway families.

As an Americorps National Civilian Community Corps volunteer, Schreiner and seven others spent February and March working on the triplex that Habitat for Humanity of the San...