I have a 2x6 subfloor and in one hallway there is an air duct running immediately underlying the floorboards. The underlying cement seems to have heaved up just underneath the duct, pushing it up just under the floorboards.
End result: when I walk on it, the floorboard is unstable and loud and in effect I am walking almost directly on the heating duct.
There are no cross braces between the 2x6's in this area and there is also no clearance (or rather minimal clearance) to brace a 2X4 or something solid across.
Any ideas about how to cross brace this floor without taking out the hvac and grinding down the concrete? Thus far I have tried a few H-clips between the floorboards which has not worked.
