A floor joist is used to help brace the floor against pressure from walking on it and storing things on it. Your floor from the side looks a lot like a sandwich starting with the main floor, the subfloor, and then floor joists. Over time a floor joist can begin to come loose, which will cause a floor to creak and weaken the floor. Heavy items like large televisions or fireplaces cause a lot of weight to be put on the floors. If you plan to begin to hear your floors creaking or are planning to put heavier loads on them you can reinforce the floor joists. It sounds harder than it is and the following article will explain how to reinforce a floor joist to make them stronger.
Places where the floor feels weak or squeaks are areas where you need to reinforce the floor joist that is there. Creaking is an indication that the floor joist may become loose via loose nails or screws or may have somehow warped. Walk the floor and listen closely. You hear a dull moan or high squeal. Your foot will also be able to tell where a weak spot is because the area will give a little. Since finding the right location under the floor can be hard count the steps from the nearest wall to the location you need to begin reinforcing. From here you will be able to find the other others easily using it as a reference.
Loose or Warped Floor Joist
When under the floor you will see the beams holding the floor in place. These are what need to be reinforced. If one is obviously away from the ceiling insert a screw from each side and through the subfloor at an angle. You will see the floor joist pull itself back in place. If the floor joist is warped or bowing you will use a 2x4 to brace them as well as push them back. Measure the space between the two joists and cut a 2x4 to fit. Place the 2x4, edge up, in place, and screw it to the subfloor. Do this for each side of the floor joist.
Metal combined with wood is a very strong partnership. The brackets will help to increase the load that a floor joist can handle. Place one bracket wherever an end of a floor joist meets the floor. Make sure it is even and flush and then screw it in place. They are more effective if you place them on each side of the floor joist. You will want to do this for each floor joist in order to properly disperse the weight of the floor. It is like a bed of nails in that one nail would impale you but 1000 nails would support your weight. This happens because your entire body weight, much like the floor, is being dispersed over a larger area.