I remember talking to a guy at Lumbermart (looks quite senior and experienced, like a boss) during a fair. He actually told me the existing parquet floor can be used to replace the batten, which means you just need to lay the floor board on top of the existing parquet. It makes some sense, because the parquet is also made of hardwood and is already level. The only disadvantage is that there are no space for the wood to 'breath'. I supposed it is the same case as S4S floor boards.

I'm just repeating that that guy told me. I, too, removed my existing parquet before laying the new battens and flooring. That's the right way to do. But if you have cost/timing concern, well you need to make sacrifices then.

I can't imagine how is your existing parquet floor 'uneven'. It cannot be more uneven than the cement floor after removing the parquets, due to the glue and parquet residue, right?

Also, you say the parquet is too thin to drive nails through? Hmm isn't it easier to drive nails through if it is thin? Cengal batten is 10mm. How thick is your parquet?

The timber flooring work is undergoing at my house currently, so a lot of things are still fresh in my mind .

1. They actually glue the 10mm Cengal batten to the floor, and then nail it down using the nail gun, so yes, the nail is driven into the cement subfloor.

2. After that, the timber planks (mine is 18mm) are laid and glued on top of the Cengal batten. Nails are driven at 45 degrees angle into the groove onto the Cengal batten. I'm not sure if the nail can reach the cement subfloor, but I think it doesn't matter.

3. If parquet is used, I don't think it will pop up easily after you lay the timber planks on top, because timber planks are a lot wider and longer. You will need many parquet to pop up simultaneously in order for the timber plank to pop up. Also, remember you will be nailing down the timber planks.

4. Yes, I have my concrete floor hacked, redone, and wait for a month to cure .