I will create a doorway in an exterior wall consisting of vertical 3-inch tongue-and-groove planks. Likely load-bearing. 
I plan to insert a 45x195 above the intended hole in the plank wall before opening it up. That is, I intend to rout in two inches deep.
Now, this might be a bit troublesome, even with a circular saw. I'm afraid there might be a lot of nails too.
The idea struck me to attach the plank on the outside and pepper it with nails into the planks. If that's sufficient, it's much easier.
On the inside, I will leave the wallpaper intact so that it's just a matter of attaching the trim without having to wallpaper over, so going right through to recess it is not a good idea.
I plan to insert a 45x195 above the intended hole in the plank wall before opening it up. That is, I intend to rout in two inches deep.
Now, this might be a bit troublesome, even with a circular saw. I'm afraid there might be a lot of nails too.
The idea struck me to attach the plank on the outside and pepper it with nails into the planks. If that's sufficient, it's much easier.
On the inside, I will leave the wallpaper intact so that it's just a matter of attaching the trim without having to wallpaper over, so going right through to recess it is not a good idea.
Do you have the ability to check if a roof truss or beam rests directly over the hole you are going to open?
If you're a bit lucky, the hole is right between two roof trusses and then you barely need to do any load distribution at all.
If you're a bit lucky, the hole is right between two roof trusses and then you barely need to do any load distribution at all.
This page might be good to read: https://www.traguiden.se/planering/...us---generellt/oppningar-i-trakonstruktioner/
What about building permits/building notifications?
What about building permits/building notifications?
Is a two-story house (from 1937) and this is on the ground floor. No window above the intended opening. The intermediate floor to the second floor is about 450mm c/c, if judging by the floor structure down to the basement.