Harry's staff is made of oak -- which is already a very hard, very heavy type of wood. I don't recall it ever being mentioned that the workings make the actual wood physically stronger, but six feet of oak is already pretty darn strong.
If you mean magical power, they both act as foci -- specially made to help Harry shape his magic more effectively and with more strength. On their own, they don't have strength (i.e., someone else without magic couldn't pick them up and blast something), but the power they do have is meant to strengthen Harry's own.
Think of it like this -- if Harry is a handgun, his staff and rod are an attachable stock and laser sight.