I have four roofs in my pile of hive parts to repair. I say "repair", but pretty much all I'm keeping is the metal sheet of the roof cover. This evening I took three of them apart and cut ply/OSB to fit under each roof cover from the scraps I picked up the other day. The covers are all different sizes, varying by about 15mm. In my woodpile I found some offcuts of gravel board that have been lying about for years. I planed them down to 16mm to make some of the sides (which should give me 5mm clearance all round on a wooden hive for the smallest one) and discovered in the process that a few of the offcuts are actually cedar. I still need some more, but I'll focus on what I have for the time being, which is enough to complete two . Hopefully I should be able to get them done tomorrow and I'll have a hunt around to see if I can find enough bits to do the other two as well. The roofs I have are many and varied in design, particularly when it comes to the depth. I've decided to standardise at 100mm plus the thickness of whatever sheet material I used. Obviously they'll have no vents, which is one of the reasons I'm not re-using most of the original timber. I did notice on at least one that the mesh over the vent openings had been completely propolised up, which probably says everything you need to know about what the bees think about them.
I have a vague recollection that I've been told that PVA doesn't work very well with cedar because of the oils in the wood, but I'll have to check on that. If polyurethane is better then I have some of that as well so it shouldn't be an issue.
The waste from cutting down the OSB left me with enough to make three more dummy boards, so I cut those down to size. I don't desperately need any more right now, but there wasn't much else I could do with the waste and they'll surely come in handy one day.
The waste from planing down the gravel boards was, err, voluminous

It filled two sacks. Fortunately I have a use for it. More of that another time, though it has just struck me that I could use it for making an old-fashioned style "quilts" to go over a crown board
James