Lay tongue and groove boards in the attic

Thanks for your opinions. I will have the posts converge on the beam. I will measure which length I need to order so that I have as little waste as possible...

I'll join in right away. Rauspund is probably the better option for the attic, so OSB boards? Anyone have a tip on where to get something cheap (possibly online?) Or rather, what is cheap, what are the usual prices? Thanks!

And someone else who is joining in.

Can Rauspund also be used as counter battens? Or is something else better recommended?

Best regards

As counter battens, the cheapest formwork boards are sufficient. I would also buy tongue and groove boards at the local building materials or timber dealer. The shipping costs online are too high. I recently paid around 1,- Euro/m including tax. Delivered free to the house. Bought 240 m. 240 m 225,- Euro.