I am currently working on a renovation project where I am converting a old Horse trailer (box) into a mobile bar. As part of this project I have had to replace the old flooring in the box. Previously this had been screwed down using self tapping screws directly into the steel frame and i could feel also that in the past someone had opted for nut and bolt.

I'm looking to get your opinions on how you think I should approach this. I am using a 18mm marine ply and it will have to sit on the 8mm steel frame. My question to the community is how do you think I should secure it down? What fitting to use and is it better to go top-down or down-top?

Just as a note, a lot of the old screws rusted, fused and then snapped off when removing.


You need to consider the spacing of the steel frame.

If the floor, for the loads you expect to put on it (you have an idea?), is not to bounce or sag then you may need to add joists. You don’t mention any and horses tend to be heavy with a small hoof print so it may be ok if you are replacing like with like.

If your new flooring is different then you should check if it will be suitable.

I would fit joists - fix them to the steel and the floor to the joists... but that is my opinion, based on doing a truck for 3 musicians years ago... storage, fold out kitchen, fold out beds etc


Assuming adequate support exists (steel frame structure) for your choice of flooring, I would think flat head stainless-steel machine screws countersunk flush into the ply on top and through-bolted with stainless washers and locking nuts on the underside of the steel frame.

They would not vibrate loose or corrode (but may need occasional tightening due to expansion/contraction of ply and steel frame).

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