Gymnasium Repair with HMI 401 Foam Gymnasium Repair with HMI 401 Foam Problem The Sault Area High School in Sault Ste. Marie, Michigan was refinishing their gymnasium floor and installing new bleachers. Upon removal of the old bleachers it was discovered that the gymnasium floor had settled along the west wall. RaiseRite Concrete Lifting (HMI’s Contracting Division) was referred to by an outside engineering firm to repair the sunken floor. An appointment for inspection of the area was made and it was determined that ninety feet of the floor had settled one and a half inches. Because the wood floor could not be removed it was decided that HMI 401 high density polyurethane foam would be used to lift the concrete. An estimate for the repair was written the next day and later approved by the high school. A few weeks later a RaiseRite crew was on-site ready to perform the work. Solution RaiseRite crew members drilled two sets of 1” holes through the wood gymnasium floor to reach the concrete slab underneath every 5 feet apart. Crew members then drilled 5/8” holes through the concrete. A total of 520 lbs. of high-density 401 foam was injected through the holes where it started to expand and gradually raised the floor back to its original height. Work was completed in less than 8 hours and was immediately ready. Floor refinishers then came in and repaired the 1” holes as part of their refinishing process. New bleachers were soon installed afterwards and the floor was ready for use at the start of the new school year.