I'm modifying the structure of the roof supplied with the building slightly so as to add long skylights above each wall: this entailed leaving off some tongue-and-groove sections and cutting others down. Most of the roof will be covered first with 50mm foil-faced insulation boards and then 9mm plywood: to make this easier to fit and to keep the edges tidy I fitted some roof edge boards supplied with the cabin upside down (they're meant to hang down from the edge of the roof):
Then the insulation sheets can be cut to fit (with a sharp knife) and the boards cut to fit on top (with a marvellous new purchase of a rechargeable circular saw). You can see here the purlins, tongue-and-groove roof boards, insulation and plywood, not to mention the black plastic sheets used to cover the roof EVERY HOUR or so during the rainstorms that plagued the day I chose to put the roof on. Very tedious taking them off, doing some roofing, putting them on, sitting and waiting for the rain to stop, rinse and repeat...
The next delivery was a 4m x 2m piece of polycarbonate roofing sheet, which was also a fun thing to carry down the path:
The skylights needed additional support and had to be raised to a similar level to the eventual roof surface, so I fitted extra rafters both to the ends and in the middle, plus some additional framing round the edges:
Polycarbonate roofing comes as part of a 'system', for which you need all kinds of sealing gaskets, metal strips, plastic fittings etc. - and it's taken a while for me to figure out how it all works (with a few mistakes along the way). However one skylight is now temporarily fitted. Next will be to fit the other, finish the insulation and boarding and cover it all with a rubber sheet - I've chosen this as a slightly more pricy alternative to tar paper, as it will last a lot longer and hopefully will be quicker to fit.