Hi,
I have a quantity of tongue and groove larch floorboards which I want to lay over an existing floor (plywood on pozistruts). I really don't want to remove the plywood. Do I a) float the glued floorboards on top of some type of membrane, b) secret nail directly into the joists on the pozistruts (possibly on top of some type of membrane?), or c) something else?
Help!!

There is a floor board glue called sikaflex looks good have not tried
it my self. See flooringguide.com.

Sika products are rather expensive. Normal PVAC glue in bottles to glue the T&G for floating installation on (sound) insulation (2 - 3mm) might be a (cheape) better solution.