Volunteers are learning to rip down plaster, pull apart walls and tear off roofs. To the nonprofit group’s long-held aim of constructing houses for those in need, Saginaw’s affiliate has lately added to its mission by doing the opposite.

As part of an agreement with the city, and with at least $500,000 from the state and federal governments, the Habitat for Humanity volunteers and paid workers plan to demolish two vacant, dilapidated houses here a week, every week, over the next two years. As for creating homes, they will build or refurbish eight houses this year.

The shift in the organization’s focus is a sign of the times in Saginaw, a shrinking city northwest of Detroit where at least 800 houses sit empty and doomed, and offers a glimpse of what increasingly empty neighborhoods in many cities may soon face as foreclosures continue.