Exterior siding repair

[lumpy]

Sent: 5/14/2008

Hi all , I am looking at a 76 brave here in Michigan , Looks as thought it will need so repair work on the exterior siding. There is rotted soft spots in certain areas,

What is the usual replacement for this , how difficult a job is it.

mike

[denisondc]

Sent: 5/14/2008

   Im afraid of answering this question - but will try.  Any motor home 30 years old that was constructed the way our Winnie were, is likely to have fairly extensive rot in the walls and roof.   You need to know what the original structure was, then can decide how you want to go at it.   Mine is a 72, and like others earlier and later, the walls were a glued up sandwich; the outer layer of .027" aluminum was glued to about an inch of Styrofoam, and the interior paneling, about 1/8th or thinner, was glued on the other side.  There were few vertical studs anywhere, just a wooden strip where the wall screws into the floor plywood, and a cap strip at the top where the roof screws into it.  There would have been areas where it had plywood instead of the Styrofoam, such as around the front windows (beside the driver and passenger) and the nose, etc.  It varied from model to model.    It was a very strong and light sandwich, but once water would get into it - the water would be trapped, and wood rot would proceed slowly for months, even years.
   The roof is also a sandwich; the interior ceiling panels, glued to the one inch or so of Styrofoam, then about 3/8ths plywood glued to the upper surface of the foam, and a .027" skin of aluminum laid down over the top.  Other than the roof edges and the various vents and skylights I don't know if the aluminum was glued to the plywood or not.  The only roofs I have 'opened up' were all so thoroughly rotted that it wasn't possible to tell if there had been glue there.   And there were very few 'rafters or 'joists' in the roofs!  Maybe a couple on each side of the roof a.c., and one running across behind the driver.  Really minimal.
   If you go to the search pages, looking in the 'coach interior/exterior' category  and look for anything having to do with 'roof' or 'rot', etc. you will find enough info to make you lose a lot of sleep.    Mine has no wood remaining in the bottom of the walls that I have found.  When we go over bumps, bits of wood flakes always come out like a dust cloud.   But it still stays in one piece.
   In the Winnebago Service Manual, among the few useful bits of information is about the gluing they used when they made the original wall and roof sandwiches.  They chose not to use epoxy glue, probably due to its expense in the early 70s.  They couldn't use glue the aluminum to the foam with any glue requiring air to dry - as the sandwich would keep air away from the glue and the wall would de-laminate.  They couldn't use a contact-cement, since its liquid solvent vehicle would dissolve the Styrofoam.
         So.... They first sprayed the foam with poly-vinyl acetate glue (a.k.a. Elmer's glue-all) and let it cure overnight.  Then they sprayed the inside of the aluminum sheet and mating surface of the foam (now protected by the skin of Elmer's glue all), and laid them together.  They had big sheets of waxed cardboard they laid between the surfaces until they had them lined up, then they pulled out the cardboard and pressed the 'sandwich' together.
    Also in that Service Manual, they showed people repairing damaged sections of the walls.  They opened up the 'pittsburgh seam' that joined the upper and lower sections of the side wall aluminum, and glued a new sheet of aluminum over the damage (after filling any holes with foam or fiberglass).  This seemed to involve 4 to 6 people in Winnebago factory uniforms placing the large sheets in place.  Afterward they would roll the 'Pittsburgh seam' shut again, and repaint as necessary.

   When I need to redo my roof and walls, I hope  I will be able to use (afford to use) the polyisocyanates insulating 4 by 8 panels that come in different thicknesses, and either epoxy glue or some other two-part thermosetting glue, that doesn't require air for curing.
    Good Luck, and please let us know what you did.  Pictures would be good too.

[lumpy]

Sent: 5/14/2008

I guess I should have let you know were the damage is occurring, It is mainly between the front wheel well rearward towards the rear wheel well about 12-15" up from the bottom.

I am making the assumption that this will be about where the floor meets the sidewall and it was due to a previous leaky roof that "trapped" moisture and hence the soft exterior rot.

[bergmarkdale]

Sent: 5/14/2008

The soft spots you are seeing could be the result of rotting, but could also be caused by de-lamination due to the glue not sticking well anymore. It's possible that the understructure of Styrofoam and  plywood is good but just not sticky anymore. If you press firmly on the aluminum skin with your fingertips (sounds silly but give it a try) and you reach some firm resistance, then at least that area is probably OK, but the glue is no longer holding. If it's total mush with no resistance, then it's probably rotted plywood underneath (but as denisondc wrote, there aren't many areas with just plywood or other wood underneath the exterior skin).  I don't think that Styrofoam ever "rots" but it could break down over time if it's in an area that should be supported by plywood.  A Michigan Winnie probably has seen a lot of wet rain or snow and I would be amazed if it weren't rotted some at the lower skirts.  If the soft spots are higher up, especially toward the "Pittsburgh" area or higher, then it is more likely glue de-lamination.
      How difficult is it to fix rotted or de-laminated exterior skin?  Obviously, if it covers large areas it is extremely difficult AND expensive to fix.  Smaller areas are more do-able, and it also depends on how nice you want your rig to look.  Look under "Pictures" on Page 5 of this Web site, motor home called Winzilla and see extensively rotted and then repaired lower skirts--a very big job!  The pictures give a pretty good look at how the sandwich sidewalls were made, but the owner has added much more plywood to the repair than the factory originally did (a very good idea).
     If the problem is de-lamination and not rotting, the repair is different.  Large areas of de-lamination are probably beyond the scope of a do-it-yourselfer, since the aluminum would have to be peeled off completely and then reattached using the glues that denisondc wrote about, and with the help of about 5 people in Winnebago uniforms.  Shocked)    Small de-laminations are repairable, but only if you can get at the backside of the metal with the new attaching glue, say for example, by taking out a window or vent or trim piece and squirting in the new glue, then carefully pressing it back up against the foam, then reattaching the window or vent or trim piece.  The "glue" that I have used is Loctite Power Grab, which works well only on small areas.  It cannot be used on large areas because it does not expand and contract with the aluminum skin.  But small areas are fine, as long as the area is accessible and you can skirt it or squeeze it several inches using a tube with a long snoot.  Spray contact glue will not work in these areas since you can't get at the backside of the metal, and thin liquid glues don't  work because they are too thin and can eat up the foam.  The Loctite works OK since it has "body" to it, but it's hard to get it to go long distances from your access hole.
      I like denisondc's description of the original "factory" way of making sidewalls.  I was a common laborer at Winnebago 1972-77 and though I wasn't a "gluer" I watched them make sidewalls because it was so fascinating.  I don't remember the Elmer's glue part, or the wax covered boards, but what struck me at the time was how uncontrolled the environment was when they made them.  The poor environment is a big reason why we have seen a lot of sidewall de-lamination over the years.  If it was 95 outside with 95% humidity, all the doors were wide open since there was no A/C in the factory.  Or, it could be -10 degrees with interior temps at about 60 with low humidity in the  winter.  They didn't appear to make any allowances for the different temps or humidity conditions.   The spray machines had many nozzles on them, some of which  could plug up during the spraying, leaving an inadequate amount of glue in spots.  Or they may have tried to push too many sidewalls through before cleaning the nozzles and lines up from that green slimy glue that they used.  I don't know how they make sidewalls now, but I imagine it's in a climate controlled environment for more consistent quality control.
      Having said that, I am amazed at the old Winnies I've seen here in Arizona that have little or no de=lamination.  But they also have little or no rot due to little or no rain.   You would think that the extreme heat here would melt the old glue, but maybe that isn't much of a factor.

[LJ-TJ]

Sent: 5/14/2008

Hey Mike try to contact a member called winzella. He has some great pictures of a restoration he is doing in the area your talking about.

[13503gds]

Sent: 5/19/2008

Why gentleman I'm flattered. Mike Winzilla is mine. Not knowing much about how they were built I bought my 1974 D-21 & learned as I tore it apart. It took my a while to figure a couple of things out but what rings true to most manufactured products is life span. I'm sure they could have built a Winnebago to last 50 years if they wanted too. But they didn't & in the process what was thought to be a good idea at the time wasn't later. Take the lower panels below the floor all around the coach. They used aluminum skin to line the plywood as it was not treated. Good idea except they also used steel staples to fasten the aluminum to the wood. Bad idea. You get galvanic dissolution taking place. Holes open up in the aluminum allowing water to seep in. No where for the water to get out. Just rots over time. Window sealing appears to be a problem as well. Water gets under the aluminum & rots the side walls. There is more to look out for but you should get the geest.

[Lefty]

Sent: 5/19/2008

I had the chance a couple of years ago to purchase 9'X30' sheets of fiberglass sidewall, Big blank rectangles, such as is used in the manufacture of modern travel trailers. It came in very much the same arrangement as the Winnebago "sandwich"... ie; a layer of finished fiberglass outer wall glued to about 1" of foam insulation, which was then glued to an inner panel of what appeared to be printed plywood.
They had about 18 sheets left over after the model year ended, and had switched designs. They had these offered at salvage price. I think they were only about $250 ea.
I had to pass at the time, partly because I wasn't needing to replace the entire sidewalls, and partly because I would not have been able to do it even if I had the panels...lol

I only mention it as a possible "option" to repairing yours, you could contact any travel trailer manufacturers that are in your area to see if they ever have leftover, unwanted materials. I am fortunate that there are three different trailer manufacturers located within about an hours drive of me. It's also a good way to get other goodies, like cabinets & such.

The coach owned by LJ-TJ is very similar to what a Winnebago would look like if these panels were used.

[13503gds]

Sent: 5/19/2008


You use to get that up here from Fleetwood when they were still in Lindsay Ontario. Much more pricey than that though. Re skinning is not that expensive & easier than ripping the whole wall off. My thing is I wondered how you fasten what arguably could weigh 5-600lbs. Considering you can't put a fastener through from the outside. Re skinning works around that.