CornerStone One

CornerStone One is a commercial contractor that handles plumbing, HVAC, earthwork, site utilities, and water and wastewater treatment for projects across Eastern Wisconsin. Its work includes hotels, restaurants, hospitals, schools, apartments, and manufacturing facilities. The company designs and builds prefabricated plumbing and HVAC systems in its own Brookfield plant, which speeds up installation and helps buildings reach occupancy sooner.

Facility service crews handle both routine and emergency calls, and the company runs 24-hour service. Bids, quotes, and proposals are requested by email, and a second office in Oshkosh covers Northeast Wisconsin. Most of its business comes from commercial clients rather than homeowners.