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Sunday, January 16, 2011

Air Leak on RV Siding

I own a 32-foot 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. What I need to find out is where the air is coming in. I am unable to determine this and I would like to repair this myself. Any ideas? Tom, (La Quinta, CA) 

Tom, if air is getting behind the siding, then water can also. I’d recommend a thorough inspection be performed. The first thing I would suggest you do is completely remove the front edge molding on the affected side of the trailer. After the molding is removed carefully clean off all the old putty and sealant and set the molding aside. Next clean all putty and sealant remnants still on the corner of the trailer. Access the roof of the trailer and 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. 

Back down on the ground, with the edge molding removed, carefully pry open the sidewall as much as possible and use a flashlight to inspect the framework behind (this is assuming you have soft side walls and stick construction). Reach your hand in and feel the insulation. Hopefully it is dry inside. If the insulation is slightly damp it can probably be dried by propping open the gap between the siding and framework and directing a portable heater into the opening. Leave it on for at least 24 hours or until it is totally dry. Reassemble the exterior wall once the innards are dry. 

A staple gun was probably 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 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 tight or they will strip. Use a larger size screw or install additional screws in that area if some are indeed stripped already. Make absolutely sure that the molding properly covers and overlaps the bitter edge of sidewall material. 

It is possible that the sidewall skin is 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. If may be necessary to “cheat” the molding further inboard so that it totally covers the edge of the siding all the way around. If the siding has dips and valleys by virtue of its design, apply more than one layer of Eternabond tape. You’ll want all the gaps completely filled in. Using a utility knife, simply trim the excess and do another thorough inspection for gaps in the sealant.


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