i had a new home constructed in the winter months of 2000. the contactor laid the sub floor but waited weeks to cover the roof. we had weeks of rain, snow & ice laying on the floors. the contractor insisted the floors would not be affected. i've had issues with the floors since we moved in. although i have 2 x 8s on 16" centers you can feel the floors flex and bounce when walked on. any ideas as to what is causing the problem and how to correct this?