This is an article about how I repaired the extensive damage on the fiberglass sidewall on my Fifth wheel trailer.

The included pictures show step-by-step, how I did the repair, including the lamination of the sheet of new RV fiberglass and luan plywood.

Travelling in the right lane on the freeway, on our way home from a camping trip, I heard some noise coming from the back. Glancing in the side mirrors, I saw something white flying off and landing in the embankment.

We were approaching a rest area, so we pulled in there to a take look. There we noticed that a large chunk of the fiberglass laminate siding on the curbside at the front end of the fifth wheel trailer had broken off.Fiberglasss wall damage on Fifth wheel trailerFiberglasss wall damage on Fifth wheel trailer

Further inspection revealed that water had leaked into the sidewall, delaminating it, separating the luan (also called lauan) plywood (which is attached to the aluminum frame) from the fiberglass.

The RV was already years past its warranty. Having the repair done at a professional RV shop would be the proper approach, but it would be quite expensive, so I decided to take on the task myself.

Replacement fiberglass roll for RVReplacement Fiberglass roll for RVI did all the necessary research on how to repair the fiberglass wall. It was going to be a challenging, but not impossible, endeavor. All the material I needed was a sheet of RV gloss fiberglass, sheet of lauan plywood, specialty glue for the lamination, Styrofoam insulation, and specialty glue to attach the laminate to the aluminum frame and to the Styrofoam.

The most difficult part of the process would be laminating the fiberglass and the plywood.

Lauan plywood joined together for RV repairLauan plywood joined together for RV repairI found all the needed material at a RV restoration supply warehouse, where they seemed to have about everything needed to rebuild an RV. The plywood, I had to get from a lumber yard

The size of the area needed to be replaced was about 6x5 feet. I purchased the roll of fiberglass by the foot, and it was wide enough for the project. The plywood is 4x8 feet, so I joined two pieces together, using a thin aluminum strip at the joint.

Adhesive applied to RV fiberglass sheetAdhesive applied to RV fiberglass sheetTo apply the glue for the lamination, it had to be spread thin on both surfaces, on the fiberglass and the plywood, and let dry.

Once the glue is dry, the two surfaces would be mated together, and the glue needs to cure under pressure. That is typically accomplished using vacuum pressure, meaning that the laminated part is completely sealed under high vacuum, pressing the two surfaces together.

Of course, I don’t have a such vacuum sealer laying around in the garage. I contemplated making a sealer, by using a vacuum pump and sheets of plastic, but instead I decided to pressurize the laminate by placing weights on top of it instead.

Fiberglass laminated to plywoodFiberglass laminated to plywoodThe recommended method of applying the glue to the laminate was spraying it on, which I did. After the glue had dried, I carefully rolled the fiberglass over the plywood, being very careful not to leave any air pockets. Once the surfaces mate, the are inseparable. If air pockets are found after the assembly, they can be removed by drilling a small hole in the pocket and flatten the pocket. But luckily, in my case, I didn’t get any air pockets on the laminate.

Fiberglass plywood laminate cured under pressureFiberglass plywood laminate cured under pressureOnce the two surfaces were mated together, I placed sheets of plywood on top of the laminate, and placed a large amount of weight on top for the curing process. I don’t have a picture of all the weights I placed on top, but it sure was way more than a few bricks!

RV side wall repair preparationRV side wall repair preparationI prepared the sidewall on the RV by temporarily removing the window and the remaining damaged outer plywood layer, replacing any bad insulation, and cutting back the fiberglass/plywood laminate to a straight vertical line, where the old a new laminate walls would meet.

I then placed the new laminated sheet temporarily on the wall, to mark and cut out a rough outline, leaving a few inches of extra margin, to be cut out later.

Adhesive applied to RV aluminum frame and replacement wall panelAdhesive applied to RV aluminum frame and replacement wall panelNext, I applied the same laminate glue to the frame on the sidewall, and corresponding surfaces on the laminate plywood.

I attached the laminate to the wall, and clamped it in place for the glue curing process. Once the glue had cured, I cut out the excess siding, and installed the window, light fixtures, and the front wall cap.

RV side wall repair completedRV side wall repair completedThe old and new parts of the wall match quite well, although the difference is noticeable. I covered the vertical, narrow, joint with Bondo fiberglass patch, and placed a strip of white tape over it.

RV side wall repair still good after 5 yearsRV side wall repair still good after 5 yearsStill, five years later, the replacement wall has been holding up well.

For this kind of work, I do strongly recommend have it done at a professional RV repair shop. But if you are a DYI guy, understand what this involves, and is willing to take the risk, go for it! If it fails, you are out a few hundred dollars, and the time spent, but you gained some experience in the process 😊.