Once again I'm thinking about using some t&g cedar planks on my bathroom ceiling (if I have enough left over from main room). Right now the bathroom is roughed in, wired, insulated, vapor barrier up (6 mil), exhaust fan, etc. I have the "blue board" for the walls but would really like a touch of the rustic look on the top, if I can. Is there any additional prep work I need to do on the ceiling before I nail up these cedar planks? e.g. Do I need to run furring strips and leave a space between the cedar and the vapor barrier?