ᐅ Roof rafters - How to install tongue-and-groove boards

Good morning everyone!

Our house is currently in the shell stage, and soon we will be insulating the upper floor and installing the tongue-and-groove boards in the attic.

The spacing between the individual rafters is about 60cm (24 inches). What thickness of tongue-and-groove boards should I choose? 22mm (7/8 inch) or thicker?

Yesterday, I had an idea, but I’m not sure how practical it is.

The area to be covered is about 3m (10 feet) wide and 12m (39 feet) long.
In the “normal” approach, the boards would be installed as shown in image 1 (red = rafters/joists, blue = tongue-and-groove boards).

Given the width of 3m (10 feet), it would be much simpler to install as shown in image 2:
Use tongue-and-groove boards cut to a length of about three meters (10 feet) and lay them that way, then add counter battens (green).

Which method do you think is more stable? I assume method 1, right?
How thick/strong do you think the battens should be in method 2?

Thanks a lot for your opinions,
have a nice Sunday!

1). Installing the counter battens does not make 2) any less complex. C.

Well, basically I think it’s easier to install a counter batten than the final tongue-and-groove boarding.

My main concern with the question was about stability, specifically rafters versus counter battens.

Does anyone have an opinion on this?

Regards

That depends on how thick your battens are.

Okay, and which batten thickness would you recommend?

Around 50 by 45 or 50.
However, I would personally choose the first option without the battens. That’s how our floor is also constructed. It’s quick and easy to nail it directly onto that.