The first decision - the deck!

[Boreal]

This is what my 5x8 H&H comes decked with:


[Edit to the weights involved.]

First, some background. This is a walled trailer, and the walls are structural. That's fine, because I want that storage underneath. I'll build the true deck on top of the wall, and canti it out 6" to give me a 6' wide bed. I need that width because I'm bunking my daughter cross-wise (this is a 2+1 sleeper) and I want to be able to use this trailer for more than two years.

So, I've taken possession of this lil guy, I've removed the ramp (and over a hundred pounds of uselessness), and am faced with this decking: over 200 pounds, I estimate, of pressure treated, 2x8 pine. The problem is that it's overkill, it's heavy, and it will need to be weather proofed to keep my storage area dry.

So, I can either...

A – keep the decking, roofing tar the heck out of the bottom, and caulk the cracks on the top to keep the box relatively (if not positively) dry.

or

B – remove the 2x8 and replace it with PT, 3/4", T&G ply, and roofing tar the heck out of that.

The benefits of A are that it's easier, quicker, cheaper.

The benefits of B are that I'll save about 110 pounds*, get a cleaner, weather proofer storage deck, and gain some elegance points.

The downside of B is the 3-4 hours of extra work, and extra expense.

Should I settle with what His Noodley Appendage has provided me, or would this be the first of many compromises that will eventually eat away at my soul?

I'm inclined to keep the 2x8 deck and make do. 110 pounds vs. 4 hours.

* a deck of 2x8 PT pine is about 200-220 pounds. It's very dry. A sheet of 3/4" ply is about 75 pounds (oh, how I hate talking pounds!) But 5/8 of 150# is 95#, say, so I'll actually be saving 111-123# in total. Forgot I wasn't using a whole sheet, doh!

[KCStudly]

If you do decide to stay with the planks I would seal the gaps from the underside with caulk before tar, perhaps in addition to doing it from the top. Or at least use that reinforcing fiber tape over the gaps that is intended to work with the emulsion over cracks and seams.

Over time, as the boards continue to shrink these gaps could open back up. That seems to suggest that ply would be better, but it may never be an issue with a flexible caulk or in our life spans.

[aggie79]

I wouldn't use pressure treated lumber anywhere in a build. The chemical treatment is quite toxic. Also, the bottom of the trailer gets very little moisture. Roofing tar will work but there other solutions too. For example, a couple of coats of latex paint will suffice.

Certainly, remove the 2x8s. There will be no way to control the shrinkage and gaps between boards. I assume that your trailer deck has perimeter angle iron with one leg up. Maybe you could rip the 2x8s down to 2x2s for a perimeter ledger for clearance over the angle iron. Then use 1x or 2x material to build a sub-frame, extending out the 6" beyond the trailer deck and underneath the plywood joints, and top it off with 1/2" plywood.

This is what Jerry did on his fine RetroKamper build:



Here's a link to his build journal: http://www.tnttt.com/viewtopic.php?p=611416#p611416

[vigilant1]

I'm inclined to keep the 2x8 deck and make do. 25 pounds vs. 4 hours.

The difference in weight is just 25 lbs? Seems too low for a difference in thickness of 3/4" of wood over an area of 5' x 8'. Is the glue in plywood that heavy?
If you keep the 2"x8"s, I wouldn't count on the gaps staying filed with any caulking products. There's a lot of seasonal change in the width of those boards, plus warpage and the rattling/jostling/racking that a trailer gets.

[Boreal]

I wouldn't use pressure treated lumber anywhere in a build. The chemical treatment is quite toxic...

Thanks for the comments and suggestions. I don't think that PT lumber is as dangerous as you think it is. It's not the old stuff, the CCA anymore. I wouldn't burn it in the fireplace, but I'm comfortable using it to build raised beds and stuff. I think the threat of EPS foam burning would ruin my day rather faster.

Aside from that I think I'm now convinced not to shirk my duties, and do the right thing by removing the boards. Looks like I'll save over a hundred pounds, which is nothing to ignore. The install will be easy, and I'll just have to shim the front and back (they lay flat on the structural members. There's going to be a 9" deep storage area in the box area, but I have to lever out over the box, since the walls are structural. That's fine; saved myself 600 bucks as compared to the alternative trailer which was truly flatbed.

[Boreal]

The difference in weight is just 25 lbs...

I goofed, forgetting that I'm using only 5/8 of two sheets of plywood.

So, installed weight of the PT 2x8 is ( I estimate) 210#. Plywood is 75# a sheet, so5/8 of 150, or 96#. I'll be saving 110#, which is not for nothing.

Looks like that's the more elegant solution.

[vigilant1]

Looks like that's the more elegant solution.

And you'll sleep better over that basement floor knowing you did the "right thing"! I'd probably swap the boards out, too, but it might depend on whether I had a good alternative use for the 2 x 8s.
Best of luck.