By Gary Bunzer, Technical Editor
Q. Dear RV Doctor: I own an older 32-foot Wanderer toy hauler. Recently on a trip, I noticed air getting between the siding and the walls of the trailer, near the leading edge of the sides of the trailer. On my return trip home, the air blew the siding out like a balloon and popped the siding out from behind the edge molding. I need to find out where the air is coming in. I am unable to determine this, and I would like to repair this myself. Any ideas?
Tom Maddow ● La Quinta, California
A. Tom, if air is getting behind the siding, then water can also. If I remember correctly, the Wanderer was constructed with what is called a “stick and tin” technique, which means you do not have laminated sidewalls. Rather, the exterior aluminum “skin” is simply installed over a framework structure without a substrate of lauan or plywood underneath. Insulation is encased between the aluminum siding, the framework, and the interior paneling — a very simple construction method only a few companies still use.
I’d recommend a thorough inspection. First, I’d suggest that you completely remove the front edge molding on the affected side of the trailer. After the molding is removed, carefully clean off all the old butyl sealant and set the molding aside. Next, clean all sealant remnants still on the corner of the trailer.
Up on the roof, thoroughly inspect the front roof transition molding for gaps in the sealant, especially close to the front corners. Do the same with any roof fixtures nearby, such as roof or sewer vents, TV antenna, etc. Be sure to clean and reseal any cracks in the sealant.
With the front edge molding removed, carefully pry open the sidewall as much as possible and use a flashlight to inspect the framework behind. Take care not to crimp, bend, or otherwise damage the flimsy aluminum. Verify it is dry inside. If the insulation is slightly damp, it probably can be dried by propping open the gap between the siding and framework and directing airflow from a portable heater into the opening. Leave the heater on until the innards are totally dry. Reassemble the exterior wall once things dry.
A staple gun probably was used to secure the edges of the siding to the framework during manufacture, but you can use small tacks or staples. Just be liberal with them. The more you use to secure the siding, especially on that leading front edge, the less chance of it pulling loose again. Apply Eternabond DoubleStick tape along the inside edge of the molding and reinstall each molding piece. Be sure not to tighten the screws too tightly. Use a larger-size screw or install additional screws in that area if some are stripped already. Make sure the molding properly covers and overlaps the raw edge of sidewall material.
It is possible that the sidewall skin was cut too short in some areas and that the molding doesn’t completely cover it. This could also be the cause of the air leak. It may be necessary to “cheat” the molding further inboard so that it totally covers the edge of the siding all the way around, or perhaps install a parallel, second piece of similar molding. You may also need to add more than one layer of Eternabond tape if gaps exist under the molding. You’ll want to fill in all gaps completely. Using a utility knife, simply trim the excess and do another thorough inspection for additional gaps in the sealant.