Waterproofing Questions

[gww25]

At one time based upon my past boat building experience I thought I knew everything there was to know about waterproofing but as I'm making the transition to building a trailer I'm beginning to question some old 'truths' about wood and water intrusion. First of all I was taught to never totally 'encapsulate' solid wood members as that was a surefire way to promote rot. Encapsulation was okay when using plywood since the laminate adhesives already act as an encapsulation membrane. However after doing some research on trailer construction it appears at first glance that trying to seal almost any component of the construction just helps to promote rot or delamination eventually over time. Of course the exterior skin has to be waterproofed by some means but a good waterproof 'skin' seems to be better than trying to seal the wood itself with paints, sealers, epoxy or other means. From what I've read it is actually better in the long run to build a totally 'untreated' frame and shell and then cover it with Filon or aluminum.
I'm at the stage of needing to decide how to treat the wood components of my build so would appreciate some input from experienced builders on this matter.

[LWW]

I'm with you on this. I've done the boat thing and from past lessons don't want any drips in the night. I'm building one of Mike's Weekenders and I'm going to fiberglass the out side using West System and 6 oz cloth. I not going to paint it inside. I'll use some foam insulaton and fabric. Hopeing to leave enough for the wood to breath inside. Larryw

[aggie79]

I'm in the same boat as you - pun intended. (Actually, I don't have any boat building experience.)

I took great pains to make the exterior of my teardrop watertight. All exterior plywood was epoxied. The bottom side of the floor also received automotive type rubber undercoating. The sides and roof are covered with aluminum.

All of the inside finishes however are "breathable". My floor is sandwich construction. The inner ply skin is not finished. I place foam exercise tiles over it and then added the mattress. My interior wall finish is 5/16" pre-engineered flooring. The top finish of the flooring is weathertight, but I did not glue the t&g joints. My ceiling is unfinished ply covered with a light "web pattern" coat of spray adhesive followed by marine hull liner.

I can't say if this is the right way to do it or not, but it is the way I did it.

Take care,
Tom

[gww25]

I think your point of having 'breathable' surface finishes is important as from what I've read a lot of the dry-rot is created when the moisture content in the framing cavity gets much above 18%. If air can get into the cavity the moisture content in most places is well below 16% unless you live up north and then condensation from the occupants can raise this a bunch.

[hoytedow]

Moisture build-up is prevented in my trailer by a ventilation fan(brush-less computer style) that runs constantly while trailer is occupied. It runs quietly and efficiently pulling in fresh drier air.