My coop where the birds are anyway, is 8x8 and I use about 3/4 of a bag to a full bag of shavings that I buy at the local feed store for 5.95. One bag of these compressed shavings, they are intended for horses, is equal to 9 cu ft when opened. I usually end up with about 1 1/2" to 2" on the floor and the same under a shelf that is about 14" x 8' that my roost sits on. I only put one bag at a time but I replace it every week to help keep the flies and odor away. It may be a little over kill but it seems to be worth the 6 bucks to me and clean up is a breeze.
Chris
One other thing....I picked up a bail of cheep hay, $4.00 or so from the feed store and I have been putting about two or three flakes of it in my run. My run is is 12 x 20 and is covered with a roof. The hens seem to like it and it's really easy to fool with. I just cleaned the run this past weekend for the first time in a month and put a couple more flakes down. It took me all of about 10 minutes to do this.