I have a ceiling fan(no light kit) over a stairway wired to a foyer light controlled by two three way switches (one in foyer, one at the top of the stairs). This turns the fan on whenever the light is turned on. How can I rewire (add a fan only switch) so I can control these two devices independently?

A two wire cable will need to run from the outlet box in the ceiling that has the fan, and brought to the new switch location, and then feed the switch with power.

Tx for the reply - I'll have to look at the wiring at the fan box more closely. (not easy since it's two stories high over a stairway !) But, basically, I disconnect the fan from the 3 wire circuit - and reestablish connectivity by connecting the incoming wires to the outgoing wires (black to black, white to white, traveller to traveller) to restore the three way circuit for the light, then connect the fan using a new 2 conductor wire to a new switch, as you describe.
Can I add the new two conductor cable to this existing box or is it too many wires by code ?

You will only need to add one wire, an additional switched hot for the fan. You can leave the light wired as is. The fan has three wires, a black, a white, and a blue or striped. Leave the white and the striped and connect the black to your new switched power source.

http://www.ceiling-fans-n-more.com/ceiling-fan-wiring.php

Sounds like it solves my problem! Thanks for all the help.