Loft boarding - gap around the edges?

[gwernybwch]

Hi all,

I'm about to start to fit chip boarding to my loft (Victorian end terrace),

I know that I have to leave a gap so that the chip board shouldn't touch the eaves (to allow air flow), but is there a recommended or minimum gap that is required?

Similarly should there be a gap between the chip board and the gable end wall? The reason that I ask is that I was thinking of insulating the gable end in the attic (by adding a 'stud wall' and fitting celotex).

Thanks in advance for any replies.