joek
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Post by joek on Nov 21, 2015 0:52:31 GMT -8
I'm about to embark on repairing the rear end of my previously restored (by me) '61 Shasta. Needless to say, I'm not looking forward to it. But there is a leak, not sure where it's coming from, maybe the window or tail light. Possibly the side seam, won't know until I open it up. But it is enough water to have attracted termites, and rot through the interior skin.
I'm considering using a liquid membrane as waterproofing. This would go on the backside of the plywood and framing, before the insulation and aluminum. Liquid membranes are the latest thing in waterproofing. We have been using it in our construction business for a few years now, you paint it on fairly thick, typically 10 mils or so, and when it dries it's forms a flexible, breathable, self repairing membrane. Since it bonds to the surface, I won't have to do the entire trailer, just all I can reach. It may not be a perfect solution, or maybe it's a solution to problem that doesn't really exist, but I can't really think of a downside.
Product I'll use is Prosoco Cat5. www.prosoco.com/products/r-guard-cat-5
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nccamper
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Post by nccamper on Nov 21, 2015 4:55:06 GMT -8
I wonder if the "wet" barrier will bleed through panels or cause delamination? I would test it first.
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RinTin
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Post by RinTin on Nov 21, 2015 7:40:32 GMT -8
It sounds like you are considering the coating as a secondary waterproof membrane? In the case of future leaks, a membrane like you describe, assuming it performs as anticipated, will cause water to build up and migrate to who knows where, sit there for who knows how long, perhaps eventually causing damage to who knows what. So, you would have to coat every possible area that the water could eventually migrate to, plus consider if/how the built up water water will exit.
I know there are people who coat their framing with CPES in an effort to stave off water damage, but they face the same dilemma. Do you have a vapor barrier such as Tyvek under the skin? If installed correctly, a vapor barrier will also act as a secondary water proof membrane. This is the route I am taking and what I believe most others do as well.
In my opinion, taking your time and paying attention to detail to insure a watertight skin is where your efforts will be best spent.
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joek
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Post by joek on Nov 21, 2015 21:25:48 GMT -8
I'd be using it a primary moisture barrier and the aluminum skin as a decorative and UV cover. Like a rainscreen system on a house, where you keep the siding spaced off the waterproof membrane a little bit, to allow the moisture to run freely and not get trapped.
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RinTin
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Post by RinTin on Nov 22, 2015 7:32:01 GMT -8
My last personal experience with waterproof coatings was over 20 years ago. Used to be they tended to lift and/or crack with age, UV exposure, and expansion/contraction of the substrate. I know they have come a long ways since then, nonetheless, perhaps without merit, I am not too keen on them.
As you say, it would be protected from UV by the skin and as long as it held up to the flexing of the trailer body it seems like it could be viable. I feel it would still be best to consider it a secondary barrier. You would still have to take care to conventionally seal the skin penetrations and openings. Also, if the coating is your primary barrier, how would you contend with the J-boxes, plumbing, wiring, etc. through the paneling? How will the coating hold up to a fastener loosening and lifting underneath it?
My thinking is that a coating could be good to help keep moisture away from the wood until it eventually evaporates. To me, it makes more sense if you live in a dryer climate than one with high humidity.
All that being said, your personal experience with the product may well prove me wrong.
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joek
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Post by joek on Nov 22, 2015 13:06:08 GMT -8
Yes, waterproof coating have changed a lot over the years. Todays coatings of this type are highly and permanently flexible. I was very skeptical of this stuff 5 years ago but have seen it perform well. And have seen the waterproofing we were using before (bituthene or other peel and stick)fail in dramatic fashion. We'll see what happens with this stuff over the years.
For wiring and junction boxes, you seal around the box or wire and all holes in the box. Same with plumbing penetrations. Care should definitely be taken care with the outer skins. They should be installed as normal, sealing all seams in the typical fashion. We don't want to invite the moisture in, but we know it will get in somewhere, sometime.
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mobiltec
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Post by mobiltec on Nov 23, 2015 8:28:36 GMT -8
Two thoughts here. I would agree with Nccamper about the possibility of bleeding through the paneling and causing staining or delamination. Second, the whole idea is to build the camper in such a way that it doesn't leak in the first place. The best protection against leakage is to build it right the first time. Vapor barriers are your second line of defense against leakage but leakage is not the intent of a vapor/moisture barrier.
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