Flooring Tutorial Video?

What sort of floor are you working on?

I installed Forbo Marmoleum on my own, after two of the local certified contractors flaked out.
It was surprisingly not that difficult.

Marmoleum is easily my very favorite choice for flooring in vintage trailers, and is the same stuff that was installed in many of them when new. In fact, the pattern that I chose is very close to the original flooring in my Cardinal. Do not confuse Forbo Marmoleum with vinyl, they are radically different products.

Ah, big difference. If you have rot or sponginess, that will obviously need attention, but more to the point it's probable that the rot won't stop with the floor. It's possible to do patch repairs on floors, sometimes, with varying degrees of success, but you need to determine the extent of the damage first.

If you're new to old trailers, an excellent place to start is with mobiltec's videos on YouTube and with vikx's book. They're both members of this forum, and are both very helpful. The first step when starting with an old trailer is usually lifting the skins, so as to determine the extent of the damage (and there will be damage, not to frighten you). That little spot of condensation damage you see inside is almost certainly hiding something that needs serious attention.

My floor was basically sound, not much in the way of rot or soft spots. There was a very small strip next to the front door, maybe 1" deep and completely covered by the threshold trim that was soft, and a spot at the front of the trailer inside one of the dinette benches where someone had apparently stepped where they shouldn't have and broke the floor, but that was it. All set for a couple of patches, right? Not so fast. I lifted the skins and found that the door side sill (the bottom of the framing that the floor sits on) was almost completely rotted, along with half of the street side. This is typical. I had to cut the good floor around the edges to get access to the sills that needed replaced, and then replaced the entire floor. It's all doable, but you don't want to make repairs that are covering up bigger damage underneath.

Short answer- if you haven't done it already, lift the skins and assess the condition of the entire trailer before planning repairs. You may already know this, but don't let anyone tell you that it's possible to safely repair an old trailer from the inside without lifting the skins.

Also, many old trailers were pretty underbuilt- I'm a big guy, and even the solid parts of my floor had more give to them than I'd prefer. When I took it apart I found that the floor was comprised of 1/2" plywood over a layer of 1/4" Masonite, which is both heavy and not particularly stiff. I replaced it with 3/4" MDO, which is a lightweight, very stiff, and water resistant product originally designed for highway signs, sometimes used instead of marine ply for boatbuilding. It's rock solid now, and as a bonus I saved a significant amount of weight.

Thanks, Rod!
As you can see I don't have much in the way of width in my workspaces, which prevented me from removing the walls altogether as I probably would have otherwise. I started to do the usual crossbracing through the middle, but really didn't like the idea of a jungle gym right where I was going to be working. There's no way I could have done my pre-joined one piece floor while maneuvering through that. This worked very nicely.

Uh...what's a "sill"?