a builder I work for always allows 5mm for skim on his frames. Hes adamant it's a better job because it's thicker. So ive just started skimming up to them instead of flush. **** em
Aren't you the lucky one!
Idiot I do work for buys 6" frames in bulk & uses them on everything ... I often have to make up 25mm either side of the door frame.
I don't have a problem with it personally, most my work is following rough bastards around & would get a bit bored just skimming pristine board work.