Is there a way to stabilize the floor?

Q: I’d like to install tile in a room at the rear of my house, but my neighbor thinks the floor is not stable enough and says the installation might crack. Is there a way to stabilize the floor?

A: A floor might be solidly constructed and adequately supported but still have a degree of “bounce” or vibration when people move throughout the room. This is usually only problem if you plan to install a tile floor, because any minor amount of deflection in the subfloor could result in cracked grout or flooring. If you can gain access beneath the subfloor, you can level and stabilize the joists by constructing a perpendicular girder beneath them supported by a system of posts and piers that connects to the ground.