underbody sealant discovery;

Been thinking about undercoating our trailer as well, as I am replacing all plywood with pressure treated sheathing. With flooring removed, easy access to the frame and 2x4 joists for cleaning, rust removal, and weather proofing. This paint also sounds usable on exposed paneling within the wheel well cover. Will keep watch to see if your discovery, is a keeper.

Kirkadie,

Thanks for the advice on the pressure treated lumber. Thought I had read sometime earlier about not using it b/c of the chemicals, but also have seen comments where users intended to use all weather wood for replacement. Using untreated yellow pine with several coats of the Fence Post asphalt paint will hopefully provide a great solution to keeping the sheathing, and the 2x4 joists dry and rot resistant. BTW - where in Ohio are you located. I'm in Columbus.

Hi Guys,

I see the above conversation, and wonder if you feel that the newer versions of Pressure treated wood apply. I found that Big Orange, has converted to MCA products-
versus the more corrosive ACQ CCA etc. The "Yellowwood" manf. claims its safe with Aluminum and yet still recommend fasteners be Stainless and or Coated, Hot dipped is Kosher as well. I would tend agree, as I found my joists were mostly still good, except for right under the door. I have a couple of those "Yellowwood" studs hanging around. When they dry out they de end up weighing about the same. So many opinions on this. So much info. Not sure what to do? I want this rebuild to really last. Thoughts?

One of my main dislikes about treated is that the lumber grade is so bad that it seems to twist and warp if you don't nail it down the minute you get it home (although that might be advantageous if you want bowed rafters to keep your roof draining away from the vent)... seriously, your only talking a few additional bucks to use nice clear knot free material.
Regardless of the claims made by the mfgs of treated lumber, it does contain stuff that's unhealthy and I just don't want that in my little living space. Don't think you'll find any modern RV makers using it either.

WOW guys, well you likely have talked me out if it. I did use some yellow-wood though, under the notorious leaking windows. I can always rebuild that later. I have too much work to do on the frame to worry about it now. I did use flashing on it, SS fasteners, and completely isolated it from the skin with tyvec. those from windows are such an issue. My thinking was use wood that won't rot so easily, use insulation that wont hold water, and design it to drain if it does leak!

I was thinking about the 2x4 floor joists that are exposed repeatedly to water and outdoor conditions being ideal candidates for pT wood.  My concerns mirror yours, fasteners? My understanding is that fasteners become an issue mainly when there is repeated or consistent exposure to moisture. The newer products claim to be less harsh. As much as I would never hope to, one of the advantages of a rebuild is that we can put it back together in a way that is easier to take a part. If I ever had to work on it, replace anything, at least I'll be dealing with screws instead of twisty nails by the thousands. 

I really only have one piece to replace, I think I'll keep the originals and just re-coat them. Indeed that tar stuff really held up well. 
My Deluxe came form Maine, must have seen some rough winters up there, so this stuff is effective. 

BTW, I just got done pulling up my floor, most of which was in great shape. Digging after those nails with a sheep's claw, I noticed that the plywood was rather "waxy" almost like a treated product. Anyone know what that is? Man that stuff was tough. 

Also, what did they use for the outside 1x2 that sandwiches the paneling, same as the skin folds under and gets attached to?
Call me crazy but mine is very greenish, and looks like some sort of treated wood? Any idea what it is? Amazing they didn't coat it with the tar stuff. 

Lastly, what is the favorite treatment for the metal frame after you've wire brushed the rust off? I have some rusty metal primer. Considered following that with a heavy metal paint.  But I would like to know the bomb proof, last forever (another 60 yrs) method. 

cheers

That's my philosophy too. I used Tuff-R insulation, it's got silver on both sides and doesn't hold water, and aluminum tape on the inner seams and frame, as a "vapor" (more of an air) barrier. Mine's got an aluminum belly though, so I didn't coat the bottom of the floor. Next time maybe!

Sorry for catching up late with this post. I did a complete frame off restore and used the Fence Post product on all the metal. Was fortunate that the metal cleaned up nice with sanding and patience. The paint product went on well and since I had bought two gallons, applied a second coat for extra protection; although one coat should suffice. I also used the paint (2 coats) to cover the underside of the all new plywood flooring. Stayed away from pressure treated lumber and used good plywood, sanded on one side. Also replaced and painted all 2x4 joists, including both side and middle flooring members. In process now of replacing/painting all lower wall siding that attaches trailer body to the 2x4 joists. Will also paint any exposed areas in the wheel wells when I get to that point. When done, will have used close to two gallons. $30 for what I feel will be great protection against future rotting. When you gut a trailer to the frame, you can really see what happens to unprotected wood over time. Using a good paint/metal sealer like the Fence Post product will provide superior protection for many years to come.