High Spots and Sag in Living Room Floor

Skills Needed: CMU Piers Constrruction

Categories: Crawl Space Repair, Foundation Repair 


Mr. B from Mount Pleasant contacted CNT Foundations after seeing a commercial on television for us during the Olympics. He was experiencing a sag in the floor of his living room midway between the back wall and the main load bearing wall, with two spots that were slightly elevated. He indicated that this had continually gotten worse since he purchased the home approximately 4 years ago. An evaluation was completed throughout the rest of the home to see if there were cracks in any of the walls above doors or windows, cracks in the ceramic tile in the kitchen or bathrooms, or other sagging, sloping or humps in the floor. No other symptoms were found limiting scope of the problem to the living room area.


After completing a diagram for the home indicating where the problem area was, a Foundation Consultant from CNT Foundations entered the crawlspace to assess the symptoms. It was found that at one point in time the HVAC ducting had been in the crawlspace but had been removed when the unit was put in the attic. That was an important part of the diagnosis because a considerable amount of moisture in a crawl space comes from condensation on sweating ducting. Moisture is then absorbed into the wood joists causing weakness. In Mr. B’s case, there were three separate issues contributing to the problem that he was having. First was condensation leading to some weakness in the joists. He had addressed that by having the HVAC ducting moved to the attic. Next was what is referred to as over spanning. This is when a series of joists is spanned further than what they should be based on the width of the board. In this case, Mr. B had 2 x 8 joists spanned almost 12’ under his living room. Over time the joists weakened and started to sag. The third issue was that at some point in time two screw jacks were installed in the crawl space because the floor had started to sag. Screw jacks are considered a temporary repair by engineers and are not designed or intended to be used for permanent support. These screw jacks were poorly installed which created humps in the floor as the floor framing surrounding the jacks continued to sink.


Because of the weakness and sagging in the floor joists, numerous joists needed to be sistered. This is where a new joist is installed along a weak joist to provide a sound surface to support the floor being lifted back into place. The rusted screw jacks were removed and then a row of 4 CMUs was installed on footers to support a drop sill. The drop sill sets on top of the CMUS and runs perpendicular across the bottom side of the joists supporting the center of the over spanned joists allowing the floor system to be evenly lifted back into position. Once CNT Foundations was completed, the sag in the living room floor was eliminated, the humps were gone, and knickknacks on shelves no longer shook when the floor was walked on. Mr. B became another satisfied CNT customer!