Wednesday, July 7, 2010
Posted by RV Doctor
One of the most troublesome things I have found to maintain are the exterior moldings which are used to seal the seams along the edges of the motorhome siding. Many times there is only the smallest portion of the siding being covered by this molding and as we know the severe movement of all parts of an RV can allow the siding to become dislodged from under the molding. Are there aftermarket moldings which allow for more coverage of the siding? I have an RV where only a 1/4-inch of the siding was covered and after the road trips and movement of the siding due to expansion/contraction from the sun, etc., is now unsecure and subject to water infiltration from rain events. Why do manufacturers seem to skimp on such a vital piece of moisture protection? I regularly reapply sealants but if the molding isn't sufficiently large enough to overcome normal movements of the siding what suggestions do you have for remedying this dilemma?Eddie, (Smyrna, DE)
Eddie, I hear you; I’ve seen your exact problem on many RVs over the years. Thankfully not so much lately as most coaches now have radiused corner sections. Basically it is due to a poor installation of the sidewall skin and/or the roofing. The sidewall skin should extend fully to the top of the roof, before the roof material is applied. The roofing, then, folds over the edge and is stapled or secured through the sidewall material and into sidewall itself. If the installers cut the sidewall material too short, the overlapping roof material won’t quite cover the top of the sidewall skin. If they cut the sidewall and the roof covering too short, there’s nothing that will protect that top edge. Some edge moldings used back then only extended down the sidewall a short distance. And like you noticed the wracking of the coach along with the temperature changes results in the loose skin and what amount to an open funnel for rain water. The only fix I can suggest, short of replacing the siding, is to install another piece of flat molding and position it just below and tight up against the existing molding. Prior to securing, re-staple the sidewall skin to the sidewall structure; it’s okay even if they show since the new flat molding should be at least ¾ or 1-inch wide. Be sure to use a butyl caulk strip behind the new molding piece. If you get a matching insert, you probably won’t notice the double molding once installed. Unfortunately, this is simply a cosmetic approach to a repair.