Welcome to Workshop. It's terrific to have you join the community. I'm sure you will find this is a friendly place where there are loads of people happy to share their experience and knowledge.
Workshop members like our resident flooring expert @PJA might have some suggestions for you.
Can I ask why you're considering using fence pailings rather than a timber flooring product? This article might be a helpful starting point - how to choose the right type of flooring. It includes various options, including timber-look vinyl flooring, which can be easy to install and laid over your concrete.
It doesn't sound like a good idea. There's plenty of low-cost flooring solutions that will look good. Or if your concrete is in good shape you might consider a polished concrete floor? Usually a "floating floor" will be cheaper though.
I knew a bloke who loved the hats that they make out of drink cans and decided to make a car the same way. It didn't last very long, because, of course, it was just a novelty.
I too, loved timber floors; timber walls, timer furniture and especially timber fences; and you could probably make a timber fence out of a large variety of timbers. Floors however, well that is a different story.
We rid ourselves of our Carpet in the living areas of the house and the life span of vinyls is 5 – 10 years. Put simply, fence palings are the wrong timber and are not intended for flooring.
It is the ‘look’ you are after, rather than the actual product.
You may be aware that I am a great lover of laminate flooring. It is more durable and far cheaper than timber or bamboo and requires very little maintenance, unlike my ex.
Bunnings have a huge range of timber design laminates and some that have that antique weathered look. Well worth checking out.
If you are heart set on the palings and have unlimited funds, I would suggest that you select a flooring timber and have it dressed and cut to look like palings.
Best of luck with your project.