18 or 22mm chipboard flooring?

Herzlos

I'm re-flooring a storage room at the back of a garage after some moisture damage, which is currently ~19mm thick (I'm assuming 18mm that's expanded).

The builders yard provides chipboard in 18 and 22mm, so I was going to go for 18mm as it's closer to the original stuff, but I'm unsure as to whether it'll be strong enough. I assume so or it won't be sold.

Is there a guide on where to use each thickness, or is it just defined by the span gap between supporting beams?

Edit: Some info from Wickes shows that 18mm is for 400mm spans, and 22mm can go up to 600mm. Does it make sense to go for more spans and thinner board, or less spans and thicker board?

Furts

The Wickes info is correct. I would add that all chipboard flooring, should(!), be green moisture resistant grade P5.

It is your choice what you go for. Remember these are minimum recommended standards - you can exceed them if you wish to do so.

With works to my home I went for 22mm chipboard on 400 centres. The result was no flexing, or squeaking, and better sound insulation.