After close to 30 years, the time has come to replace the pressure treated boards on my trailer. There are 10 of them and they are 16' long. They are held to the crossrails with large torx bit self tapping screws. Some have popped the heads off, some have worn thru the boards. The rest are seriously rusted in place. Any suggestions on how I should hold the new boards in place? At the back of the trailer the boards slide into a U channel facing forward. That should hold them there. At the front, I was thinking about welding a piece of steel tubing from side to side on top of the boards to sandwich them down. That should lock them in the front. Best idea I can come up with for the two cross rails is to remove/drill out the old fasteners, and enlarge the holes, then drill up into the boards. Once the holes are all the way thru, I can use regular bolts with lock nuts on the bottom. Thinking about leaving center open and running some PVC tubes in there to hold the poles for my carport canopy. Anybody done this before?
My experience is that a lock washer and nut in that configuration will lose nuts off the bottom at about one for every 300 miles of travel. Double nut bolts or just use screws ftw.
I use 5/4 decking boards on the trailers I build, and space the cross braces accordingly, but when I replace 2x lumber on a trailer someone else built I usually notch the boards and put a 1/4x1 1/2" strip of steel across the top above the cross braces so it is flush with the top of the wood. It's a little more wood work, but then I can bolt it down every 8" or so (or between the boards if you are leaving gaps and/or notching the sides of the boards) and there's a lot less drilling and bolting. I'll usually step up a size or two on the bolts too, 5/16 or 3/8 vs whatever it came with.
Don't try drilling up from the bottom so you can reuse the existing screw holes. It's a huge pain in the rear for very little gain. Just grind the existing screws off smooth with the top of the cross rail and snap off what sticks out the bottom if it's where you need to put a nut. If you are worried about too many holes just weld up the old ones.
I used carriage bolts and fender washers on the deck; washers, lock washers and nut below.
Not a car trailer, but I replaced the decking on my. Snowmobile trailer a couple years ago.
I pried off the old decking, which was probably easier than yours since it was plywood. But you might be able to use an air chisel to snap the heads off, or angle grinder to cut then, and strip the boards.
The original decking was held on by self tapping screws and a piece of angle the overlapped the front edge of the plywood and bolted to the front face of the trailer frame.
Once the old wood was off I used an angle grinder to cut the screws flush with the frame channels so the boards would sit flat. I painted everything with Rust converter and painted the trailer with rustoleum rattle cans.
I placed the new wood on the frame and had a helper drill holes while I followed with new self tapping screws. It went fast and no issues trying to line up holes.
I figured the original wood and screws had lasted 20 years, so I didn’t see a reason to spend a lot of time or effort trying to get improve on it.
I wouldn’t overthink it, and just go with the same self tapping method used for the originals. You got 30 years out of the current boards and hardware. Are you really going to improve on it by enough to justify spending a lot of time and effort trying to do something else?
No Time said:
I wouldn’t overthink it, and just go with the same self tapping method used for the originals. You got 30 years out of the current boards and hardware. Are you really going to improve on it by enough to justify spending a lot of time and effort trying to do something else?
My thought as well. If it were me I'll probably be dead in 30 years, so it would be a lifetime fix. 
The question I have is do you use the trailer for hauling cars only? If so then I would suggest replacing the wood with steel diamond plate. I have an open trailer that came with a full wood deck. I later removed the center boards to make room for poles for a canopy and since I only used it to haul cars I didn't need the center boards anyway.
I later decided to "rebuild" the trailer. I had a steel fab shop cut up some 4X8 ft 1/8" thick steel diamond plate into 16 inch wide pieces, I also had them put a 1" 90 deg. upward bend on one side. I then welded the sheets to the trailer. It has held up a whole lot better then treated lumber.
Based on life with an old trailer with a wood deck I think you should do a quick gut check on Make vs Buy. I found through some research that it was a close call between purchasing new and transferring custom mods over vs the cost and time to rebuild it.
stuart in mn said:
No Time said:
I wouldn’t overthink it, and just go with the same self tapping method used for the originals. You got 30 years out of the current boards and hardware. Are you really going to improve on it by enough to justify spending a lot of time and effort trying to do something else?
My thought as well. If it were me I'll probably be dead in 30 years, so it would be a lifetime fix.
I was going to write the same as No Time. Wreck out the old deck, grind off whatever is left, rust proof and redeck with self-tappers.
Or sell it as-is and buy a new trailer. They hold value well and it may be a better approach than fixing it.
linky
Use this stuff! you'll need to ship it but hardwood you'll do it once. I urethaned a 20ft truck box it looks great and has lasted a long time draging cars in and out.
I went through this with a co-worker. He wanted to replank his 20+ year old trailer. He was trying to overthink how to redo it when I pointed out that the planks on it were as old as the trailer and still holding up even if they were ugly and on their way out. At almost age 60, the new planks would probably outlive him.
