Okay, here's the challenge: I need to figure out just how the subfloor will secure itself to the trailer. I know this is probably something I should have gotten ironed out before building anything, but hey, I had a lot on my mind.

Let me set the scene for you:

The floor is framed 16″ on center, and the joists correspond exactly with the trailer c-channel ribs, which are also at 16″ on center.

We removed every other deck board from the trailer before we started building. The deck boards were secured from above through holes in the c-channel. These machine screws actually thread through the holes on the trailer ribs and make a very strong connection to the steel:

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So now, I have what I think is a challenge. I'd ideally like to connect the metal of the trailer directly to the wood of the sub floor.

Here's what I'm thinking: on the trailer ribs that have open holes (where we removed deck boards), I'll enlarge the holes so they are big enough to allow a 5/8″ lag bolt pass through up to a 2X4 joist. This will require some drilling through metal, which I'll admit, I'm a little scared of.

There's also a gap- because where there are existing open holes is where we removed a 2×6 deck board. So I was thinking that we'd also put a small block of PT 2X6 back in above the rib, so the lag bolt isn't just exposed in the middle.

Another Possiblity

My trailer also has these nifty stake pockets all along the sides. I was thinking of maybe doing something with hurricane clips to secure these to the edges of the floor framing, but I couldn't find a product that was a simple L bracket.

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My questions:

Does my plan (above) sound good?

Should I just try to find longer machine screws and go into the wood or is my instinct to use lag screws for wood better?

What about the stake pockets? Should I use them in my attachment system or just leave them alone?