Vapor barrier or not? And “water proofing”?

I'm kinda new to working on Shasta's.

I'm curious, how do you remove the sidewall skins, without removing the roof skin? Does the roof skin not bend over the wall skins?

The purpose of installing a vapor barrier is to prevent the warm moist air inside a trailer from being able to directly contact (and condense) on the inside of the cold outer aluminum skin. If you omit the usual fiberglass insulation, and instead use a ridged styrofoam sheet insulation with taped edges works the same as a vapor barrier. You want to do everything possible to eliminate any possible contact of the interior warm air with the cold skins. In my opinion, most wood dry rot comes from this constant condensation running down the wall framing, NOT exterior leaks. Just my observation over the past ten years of rebuilding vintage trailers.

John

“Should we add a vapor barrier, even if it is just for the sides? It’s survived 50+ years without one.”

Under cover any camper will survive. In the desert most campers will survive. On the east coast where it rained 5” last week nothing will survive 50 years outside but a vapor barrier will help.

I second john’s question, how did you get the sides off with the roof on?

Let's explore..........at night that window makes moisture like crazy.  Yup! it sure does.

It's a difference in surface temperature.  The outside surface is cold, or at least cooler than the inside temperature.

The inside surface is warmer, and has moisture from people breathing, a pot of boiling water for the spaghetti, and maybe a coffee pot brewing.  It's exactly the same thing that happens when you take a hot shower and step out to find the bathroom mirror all steamed up.

I'd bet that the window collects water "only when camping" with people and food preparation, not when the trailer is stored at home.

Well guess what........the very same thing happens to the entire inside of the aluminum skin on your trailer.  You might be able to wipe up the water on the window, but you cannot get to the water that condensed on the inside of the skins, which is going to rot your newly repaired wall framing.

I think anything you can do to seal, or at least slow down the travel of the warm moist interior air from contacting the cold skins will improve the cycle of wood framing rot.  Solid Styrofoam, cut to tightly fit into the wall/ceiling studs pockets, then sealed with aluminumized duct tape becomes effectively a vapor barrier.  On a stick and tin style construction, using a house wrap over the entire wall and roof area is a easy choice, but for the riveted skin style trailers it does not work.  On the riveted skin trailers it's easier to just install the foam sheets from the inside, then tape them to get the air seal.  I used 27 full 4' by 8' sheets of Styrofoam on my Spartan for insulation.  I always have my vents cracked open about an inch even during a rain storm (no they do not leak during a rain).   

When installing Styrofoam on the ceiling of a canned ham, you can take a straight edge, and a single sided razor blade and cut one inch wide kerfs into one side.  The cuts only need to cut the plastic sheet.  With one side cut, the sheets will easily bend into the curve to match your roof curve.  It's easy to do, and not messy if done with a razor blade.

John

Thank you for the reply! I suppose we did take the skin off the top... we undid it around the top to take the rails and side skins off. We haven't lifted it fully off, though, and weren't planning on it. I've seen the mobiltec videos where the skins were lifted off and elevated with a pulley system. Should we lift them, and if so, is there a good way to do it? 

Thanks! 

There's lots of ideas on how to do different operations.  You need to use what ever works for you best.

I'm a old guy and like to be efficient and to do the best job the easiest way.  No matter how you choose to remove the roof skin YOU HAVE TO STRAIGHTEN THE BENT OVER EDGES FIRST.  You might ask why?  Because if you move the roof skin around even just a little it will very easily tear at the bent over at edge.  There's no possible way to rebuild the wall framing edge wood rot and end up with exactly the same radius, same width, same height walls.  The right and the left wall frames did not match each other when they were built sixty plus years ago.  So.........when you put the old roof skin back on after the trailer is rebuilt, you will be VERY LIKELY BENDING THE EDGE IN A DIFFERENT LOCATION by a 1/8" or so.  It's even better if the metal bends in a slightly different location so it does not crack.

Do yourself a favor, try your very best to rebuild the trailer width about 1/4" to 1/2" narrower than original, if your plans are to reuse the original roof skin.  If by chance the rebuilt trailer ends up 1/4" wider, and you are using a original roof skin, you are screwed!

Here's how this 70 plus year old guy removes a roof skin by himself in a driveway without any fancy pulleys.  Pull all of the staples/nails/screws first.

Straighten all of the edges with a piece of 2 by 4, and a plastic faced hammer.  If I still have a little bend left, I use a "flat faced" auto body hammer and a auto body dolly and hammer it flat.  Do not use a crown faced hammer because it will stretch the aluminum.  Be careful remember that aluminum is very soft and over working it will stretch it, which creates more issues for you down the road during the remounting.  Just work it flat and stop.

Roll up the roof skin into a roll about 12" to 18" in diameter.  Have two Irwin clamps ready.  I use the kind with the flat pads and clamp the edge on each side with one clamp.  Crawl up your ladder, balance the rolled roof skin on your shoulder and walk down the ladder.  It goes back on in the reverse order.  It's not heavy, but it can be bulky if you do not tightly roll it and clamp it.  To store it while your working on the framing, just stand it on end and place a motorcycle strap around it so it does not get knocked over.

John


 

You can also "FLOAT" the roof and yes, it should be. The process is placing boards under the roof and sliding it to the side 8" or so to do edge wood inspection and repairs. If the wood isn't in too bad of shape, this is an easy way to fix things. Tie the roof down well when done for the day.

I've also slid the roof metal off and rolled it. Depends on the situation.

Pay attention to John: straighten the roof edges before moving the metal!

Thank you, everyone! We ended up floating the roof as Vik suggested with 2 by fours running under it. It worked out great and we were able to slide vapor barrier between.