Go to: http://www.cedarbureau.org You'll get everything you need there.Good Luck.
I will be installing cedar shakes on an external wall. My framer says simple Tyvek is acceptable as an underlay however I have also heard that #30 felt is the way...
Thanks Glenn. I checked around the Net and read that it will swell if it gets wet - a concern for my with small children and a planned bathroom on the second floo...