Some people seem to think that fixing bouncy or sagging floors can be a DIY project that you may be able to fix with the addition of a brick or a stack of wood. However, you should always consult an expert if you’re experiencing issues with bouncy floors.
It’s true that this method of providing additional support, also called “sistering,” can be beneficial in some cases. However, this additional support will only last for a short period of time. If the floor joist is bouncy because it’s over-spanned or full of wood rot, you’re just putting a bandage over the problem rather than addressing it head-on.
Incorrectly supporting the floors can sometimes be worse than not supporting them at all. Cinder blocks can tip or crumble, which can damage your home when they fall. Jacking up floor joists very quickly can cause the floor to buckle and drywall cracks to form. Using any pieces of wood may just add fuel to the fire and allow mold and wood rot to spread.
Clearly, the only answer is to contact a crawl space expert to fix your bouncy floors. You want the job done right the first time, and the only way to do that is to contact a JES expert for help.