I installed carpet in my 2001 Keystone Litehouse a few years ago after a water leak had stained the underside of the linoleum. I purchased the carpet at Lowes. They sold it off the reel by the linear foot. It came 12 ft wide. It already had a foam type backing and I used a brass floor trim near the entrance and at the door to the bathroom. This allowed me to retain about a 2ft x 3 ft area of linoleum at the door to place a rug and contain any dirt or water. All the other areas required the use of a double sided tape. This is about 3" wide and was sold in the same area as the carpet on the rolls in the store. The major obstacle was removing the sofa in order to get the carpet all the way out to the side of the trailer. We used the trailer for about 3 years after this install and the carpet looked good as new when we traded the trailer in. It definitely made the trailer feel warmer during fall camping.
2007 Georgetown 370TS
aka - RAYNMKR