Active job

Fix sunken and Water damaged Chipboard

I had a HWC burst in a rental, no major damage, and now a portion of the hallway has sunk. Had a look underneath the house and surely the chipboard has broken from the weight of people stepping on it while it was wet. I did a temp fix and nailed a block but need to replace the chipboard. I don't want the carpet pulled up so it must be fixed from underneath the house. Photos show with areas circled where it is weak. I wouldn't say it's more than 1m long with the width between the two beams about 410mm if that helps you. Another area of the house i would like fixed (Not water damaged) is at the entrance of the house, literally at the entrance. Not collapsing but you can feel there's a gap. A while a go I stacked blocks of wood but now it appears to not be doing much. The stack must've sunk in the ground from the weight of people pushing down on it. Again i do not want the carpet ripped up. Photos of work done must also be included. Also any insulation must be put back in it's right place.