im having trouble with the first jack rafter measurement to keep all the rafters on 400 centres. Can anyone advise ? Thanks
Your last rafter should abut the hip at the ridge , then all you do is hook your tape on the last rafter and mark 400mm across onto the hip , put a pencil mark on the hip. Then measure from pencil mark to a 400mm mark on the wall plate.. Or you can use a ready reckoner, in the book it tells you how much jack rafters decrease by .. what’s the pitch of your roof ?
Thanks shytot My roof is 42 so my jacks decrease 538 mm But from what point on the jack side cut do I measure? Long side , middle or short side. Cheers
I measure from the long side . Just treat it exactly the same as you cut your common rafter, what ever method you use to measure a CR do exactly the same for Jacks .