My new (old) garage needs a new floor.

There were railway sleepers laid out, and I’d thought of over boarding them to make a flat floor, but when I started looking into it, the sleepers had gone rotten from below.

The section I need to concrete is 16’ x 12’. Guess the concrete needs to be 4” thick, so to my guesstimate that would need about 2 cubic metres of concrete?

The base is old cobble stones, so damp proof membrane would be needed. Thinking about putting board over the concrete afterwards, and possibly Lino for easy clean and warmth underfoot.

So - guess I shutter sections off so I can make level - about 4’ wide?

Also, should I get readymix or get a mixer and mix as I go?