I'm stripping down an 18' car trailer and sandblasting, repainting, rewiring, redecking, re-fendering, and adding a winch and battery.

My main question is, what is the best coating for the wood decking? I plan on using 16' pine 2x8's (plus small 2' board for the dovetail).

 

I would personally use pressure treated 2x6. Then it doesn't need to be coated.

 

There's lots of different finishes that would work well, and they all will need to be refinished at some point. I'd be tempted to leave the bottom of the planks uncoated for that reason,so moisture can migrate through if it gets in through a void. Pressure treated is certainly an option, but that pressure treating is very corrosive to any fastener that isn't stainless steel. it will also corrode the steel frame of the trailer where it contacts unless that is very well painted first. You wouldn't believe the corrosion I've seen in even the better quality galvanized nails when I've done repair work on pressure treated decks.

 

DO NOT use the new treated (ACQ2) lumber on your steel trailer if you intend to keep it, just like 95van stated, it will eat the metal, ESSPECIALLY in high mositure conditions...the moisture literally feeds the fire that will eat your trailer frame alive....ask how many thousands I spent in material and man hours sending my guys out fixing all the damage done by this new sh.t, and supposedly the manufacturers "had no idea"....yeah right. I could burn up a page about this.

If I were to ever own a wood decked car/utility trailer I would buy the wood they use on OTR trailer floors, it's a tounge and groove set-up, wood is like a rock already, and when I ran the OTR repair shop and redecked trailers or owner ops would buy new trailers, the first thing the owner ops would do is get some of our used engine oil and mix it with linseed oil and apply to the decking and let it sit in the sun and dry...gave it a rock solid finish. We hauled 90% heavy equpiment and when the trailer were done in this fashion the tracks on the smaller D series cats would'nt even dent the wood...usually we had to put plywood down on the deck to protect it...but when the decks were treated with the used motor oil/linseed oil finish...after it fully cured that was the toughest stuff I ever seen...sounds weird but it worked VERY well!!!

just dont use treated...would rather see you use normal construction grade lumber and paint it/seal/stain it knowing it will only last awhile, but at least your frame will remain intact. my vote for 2x6's too, 2x8's warp/cup like crazy with just a few wwet/sun cycles.

 

That's funny. A friend of mine said that oil leaks from vehicles/equipment on his trailer is what saved the decking. Makes sense though.

If a guy was to paint, stain, or seal it, what would be the best option?

Would a hardwood be preferrable to pine? I would think it would be more durable, but it would weigh considerably more. I could maybe get some rough sawn oak or ash boards as I have a relative with a sawmill set-up (who mainly trashed the deck of the trailer by the way, so he owes me).

 

see what it'd take to diamond plate it. I've had a few frinds who ended up going that route and like the steel open trailers I have...they're sold on no more wood flooring. Just price it out once and see how they treat you locally on steel pricing.

A good hardwood would be ideal, but if your buddy has a mill, that will mean your getting the boards cut fresh, and that is not a good thing either unless he has a big oven to dry it out in. too much moisture fresh off the log, esspeciually once you start getting into the center of the tree. So these would have to sit for a while before they'd be "stable" enough to use and not warp/cup like crazy within a day-week of installation.

 

You understand the trade off between hardwood and pine perfectly.
I've never checked with a moisture meter, but I don't believe the center of a tree contains more moisture than the outside. As a tree grows, moisture is drawn up from the roots throgh the bark of the tree, not the middle. In 20+ years of working as a carpenter and reading about wood working, I've never heard that claim made before. Not tryong to slam anyone here, but I just don't believe that is correct. Rough cut lumber is fairly dry after curing for a year; and if cured under a covered shed for a year or more - I've noticed it behaves pretty much like kiln dried, with no shrinking when used for trim inside a home. Using used motor oil for cheap waterproofing is an idea that's as old as the hills, my wife's great uncle has a wood fence he protected that way. Perhaps not the most environmentally correct way, but it works. So does boiled linseed oil ( I think its pretty much all boiled now - but if it isn't, it will stay gummy instead of drying ). I find the idea of mixing them interesting.

 

I am counting on my flooring being replaced almost annually, so I am just using 2x6s on the tread areas, and 3/4" ply in the middle. It's a 16' deck, 4' beavertail, and 6 1/2' between the siderails. I am making sideboards to bolt to the rails, and a rear board that fits into a couple stake pockets in the deck to carry gravel and the like.
I have added more bracing to the floor to help with capacity.

 

Silly question, but is it an enclosed or open trailer?

 

It's an open steel flatbed. 16ft + 2ft dovetail. I see you are in Fargo. I am in Thief River Falls, MN. I lived in Fargo for 4 years while going to school at NDSU.