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I have a small utility trailer ta her has a corrugated metal floor. Not sturdy enough to haul my motorcycle so I want to install a wood floor using 5/4”x 6” treated lumber. My question is what is the proper self tapping screws to attach wood to 1/8” angle iron. Some videos suggest 12-24x1 1/2 inch self tapping screws, but I cannot find those locally at any of the big box stores and have no idea what a comparable screw would work.

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  • You're looking for something like this which are in stock at my local store. Those might be too long, but that's the basic idea.
    – JPhi1618
    Commented Oct 28, 2019 at 16:01
  • wouldn't anchoring the wood so tightly cause buckling as seasons change?
    – dandavis
    Commented Oct 28, 2019 at 16:56
  • DIY Trailer improvement? Corrugated metal for a floor, what? Self tapping screws for 1/8" steel, X +dozens of screws, that sounds like hours of work. Consider drilling holes and attaching wood runners or perlins with bolts/nuts and then screwing deck boards to them.
    – Alaska Man
    Commented Apr 22, 2021 at 19:57

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I strongly suggest that you upgrade to 2x6 (1.5 x 5.5") The extra quarter inch makes a big difference.

I would suggest using the hex head screws used to fasten down sheet metal roofing. You can get them in various lengths. They take a 3/8" socket.

Self tapping screws are fine for sheet metal -- say up to about 18 ga. I wouldn't want to use them on something like 1/8" steel.

Drill your holes in the frame before putting the planks in place. This allows you to drill DOWN instead of up, with no risk of getting metal shavings in your eye. You still will have to put the screws in from the bottom.

You also may want to put a pair of boards under the motor cycle. The motor cycle is a point load -- all the weight is on the two tire footprints. This is at most on two planks for each.

I have a 5x10 trailer with 2x6 running crosswise. I use it to haul up to a ton of trees, but that's well distributed. I've noticed a certain springiness on the deck, and would want a stronger deck to use to haul my ATV or compact tractor.

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    I do agree with 2x6 but my flatbed trailer is put together with flat head torx self tapping screws , I know this as I have had to replace some of the boards. I do use tek, screws into 3/8 steel I beam regularly I use #14 at 3/4 and 1-1/2” quite often to mount hardware as long as the drilling tip is longer than the thickness of the metal they work for me, if going through thicker material they may work but sometimes break off.
    – Ed Beal
    Commented Oct 28, 2019 at 17:00
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sturdy enough to haul my motorcycle

If you care about your bike and don't want to see it pass you on the highway, use stainless or galvanized carriage bolts @ 1/4 or 5/16 or 3/8 size with a nylock otherwise a nut with lock washers to hold the wood floor board down. And you might want to bolt in some cross piece 1x1 or 2x2 inch angle iron to further support the wood floor as necessary to old a 500+ lb bike. And make sure your tie down anchor points are into a good part of the frame. don't underestimate the forces the bike will see on the trailer bouncing down the road. I wouldn't use self tapping on anything except maybe the trailer lights and license plate.

look at wood uses in floors in horse trailers for a good reference...

https://www.doubledtrailers.com/horse-trailer-floor-failure/

https://www.equispirit.com/info/trailer-talk/horse-trailer-flooring.htm

and i wouldn't buy 2x6 pressure treat from depot or lowes it's garbage, find a lumber yard that sells straight (not warped cracked) wood

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