Putting new wood on trailer

I'm fixing up a older utility trailer and I'm going to put new wood on it (didn't have any when I got it) What kind of hardware should I use to attach the new boards? It will be treated wood so corrosion is a concern. Mike

Stainless steel carriage bolts, stainless lag bolts, deck screws meant for treated wood- next step up from galvanized, sort of gold color. Self tapping screw meant for trailer use. I use 3/4 treated plywood on a couple recent small trailers with 1/4 inch carriage bolts and lag bolts. RN

depends on how you want to do it Mine are fastened on the ends , I have angle iron caps , [sandwiched] the ends and welded in three places along the width, the boards are free to expand as they will get wet and contract upon drying, If you don't seal them every so often they will split if bolted and need replaced more often.

I think you should use galvanized hardware for treated lumber to resist rust.

I assume the trailer has flat steel surfaces to attach the floor to and that you have prepared the surface and repainted it and have rewelded any cracks.

My observation is that the treated lumber, which has been pressure treated green, will warp as it dries unless it is fastened securely. There is treated lumber availiable which has been dried before treating and If you haven't already got your lumber I would look into that.

Commercial trailer makers use a self tapping special screw. Don't know if they are availiable to the public. They are flush with the surface of the wood when installed. Don't know if they are availiable galvanized.

I don't like to use carriage bolts. While they have a round top and the cargo won't catch on them, the soft lumber won't hold the bolt tight to retighten sometime in the future or remove if you need to change the boards. You will have to cut them off. Hex head machine bolts with a washer under them can be tightened, retightened, or removed at will, but they may catch on the cargo. If you are using 2 inch thick boards you could counter sink the holes so as to get the bolt heads below wood level, using machine bolts and washers.

Assuming you are using 6 or 8 inch wide boards, you need 2 bolts for every support and 2 in each end. Probably 1 bolt in every other cross support would be sufficient. Don't know how wide apart your cross members are, but on commercial trailers they are 18 inches apart.

That's the only choices I'm aware of. I'll repeat the advice to use galvanized hardware. Wouldn't hurt to grease the bolts to resist rust also.

KEH

I worked in a factory making box trucks and the floor used similar screws like you described but we drilled a hole that was slightly smaller than the screw which required a impact to install, they had a star type drive to them. As far as the wood goes would I be better of getting untreated wood and sealing it to avoid the warping?

I just put a deck on a small 6x12" trailer I built and found some self drilling screws at Lowe"s. They were for attaching wood to metal studs, and have big diameter countersunk heads. I had to predrill the holes first and they were a bit expensive - around $25 for a small box. I would stay away from carriage bolts. They"re easy to install but you end up having to cut them if you ever need to remove them. The self drilling screws will probably end up rusting in the holes and will break if you try to take them out, too.

Log onto mcmaster dot com. They have all kind of bolts.

I have a 16ft flat bed and just hold the boards in at the end with a peice of angle iron welded to the end frames.

You can use flat bar at each end of the boards instead and just bolt it down on each side. That makes it easier if you ever have to replace a board or the whole floor sometime down the road. I sure wouldn't use any kind of bolts on a traier shorter than 20ft.

I use 1/4 or 5/16 inch self tapping countersunk head screws that drive in with a Torx bit.I buy them by the bag at Fastenal.Mark

Mike, most of the truck bed screws are 2 1/2X1/4 coarse thread self drilling that use a #30 torx bit to drive them. There's a couple of little wings that stick out just above the drill part of the screw. Use two drills, one to drill a hole just a bit smaller than the screw's drill bit. The other drill drives the screw in with the #30 torx bit and should go slow and have a fair amount of power. These screws won't rust off for a long time unless they are exposed to manure.

How thick is the framework? I know these things will go through 3/16 without twisting off. Jim

Re treated vs untreated lumber. All treated lumber dosen't warp. The pieces I have seen warp had obvious defects in the wood. Pick through pile and get straight grained wood with few knots. However, I prefer white oak lumber, again picked for straight grain and few small knots (or no knots). If you can find a local sawmill you could pick out a log with no branches and get him to saw that one, however you would be expected to take all the lumber from it with whatever unseen defects. For a small trailer 1 inch thick boards of oak would be fine, if having a log sawed I would want the boards 1 1/4 inches thich to allow for shrinkage when drying. If you install green boards and bolt the ends the board will shrink and probably have some small splits. Spaces between the boards will widen as the wood dries. Green oak would really need to air dry. Probably 6 months dried under shelter would be enough. You could Google "air drying lumber."

I like to coat the boards with used motor oil, on both sides before installition, once every year or to afterward. Galvanized bolts would still be better since tanic acid in the oak will react with the steel bolts and the wood will rot around the bolt. However this won't happed for a long time, especiall if the wood is oiled, and IME an oak floor with ordinary not plated hardware will last 20 years.(I'm in SC)

I use 8 inch wide boards. Wider ones are more likely to split. The sapwood, lighter in color and just under the bark, decays quickly so don't use boards that have sapwood in it.

Like to see pics of trailer when finished.

KEH

Its Foundation Grade treated lumber that's kiln dried after treatment. I decked a trailer about 5 years ago with 2x6 and 2x8 covering 16'. Crosswise planks. They are HEAVY, but so far there are NO cracks opened up from the wood drying. One plank has warped about a half inch in the middle of the span between frame rails. I clamped each plank tight against its neighbor and used the trailer deck screws that I bought from McMaster-Carr that are now more available than they were those years ago. I've not tried to remove any. I expect many won't come out easily since I've used the trailer to haul a tank of 32% liquid N fertilizer and it has spilled when the vendor over filled that tank. Running only 325 gallons through a 6" diameter hose makes it hard to shut off precisely. That's nearly 3600 pounds of fertilizer, on a couple axles, it works fine. Spills have been hosed off, but the countersunk screw heads probably didn't get cleaned. With the empty plastic tank in place, the trailer weighs right at 2000 pounds.

Gerald J.