No different than a room remodel, you have many different options for wall coverings in your trailer, including nothing but bare or painted wood. I choose to cover the bare wood for the same reason that I choose an aluminum frame: I want this to be my last trailer and I don’t want the elements ruining the hard work and money that went into it. Things such as road salt and moisture can cause significant damage over time.
For those reasons above I choose to use FRP or “fiberglass reinforced plastic” panels. Often used in bathrooms these 4-foot by 8-foot flexible sheets provide a great moisture barrier and really give the trailer a professionally finished look. The fact that they are white makes it easier to see when light is diminishing or nonexistent.
FRP installation can be messy and it is recommended that you wear gloves and put cardboard or other protective materials down. Cuts can be accomplished with a circular saw and free handed down a chalk line. Have a friend keep a shop vac at the ready—it makes a serious mess.
If you are keeping the factory edge like I suggested with the plywood and just cutting off the top to fit, you can have the hardware store stack the sheets together on a vertical panel cutter and make the cuts for you at little to no cost. The trouble, saved mess and almost guaranteed straight cut is worth it.
FRP can be attached several ways, and often is attached via numerous methods. I choose to drill a few small pilot holes for screws near the top, which will eventually be hidden by the trim piece. This allowed me to secure the panel as the adhesive dried.
The FRP adhesive is troweled on with a notched 3/16- to 1/4-inch tile-style trowel. Make sure to get full coverage on all of the edges where it could start to peel back.
A putty knife should be kept handy to help each sheet slide into the trim pieces that keep them square and edges hidden.
Don’t worry about the edges or the top being perfectly straight, a quick zip with a router will make for clean and smooth edges.
Capt. Ross Robertson