Timber framing opening for 838mm door?

[theflyingpig]

Hi all,

When I look at structural opening tables for different door sizes the most common reccomendation for an 838mm door seems to be 904mm...
I'm a bit confused by that! Surely the liner is only adding 40mm?
If I was building a stud wall and wanted to leave an opening for am 838mm door, what width opening in the framing would people reccomend?

Thanks!

 

[Notch7]

Door linings should be about 27mm

so 838+ 5 for door margin + 27 + 27 + 10 to allow pack lining square into structural opening = 907

so make structural opening 905mm or 910mm

 

[theflyingpig]

Thank you!