carcassing

Hello! My 5x2 are slightly too short to go from ridge beam to eaves when framing out my velux - is it possible to join two pieces (which themselves will be bolted to existing rafters) or does that contravene building regs?

Anyone done this? My local timber merchants are doing 22 x 150 sawn treated at a decent price, I've been using it for a lashup (fixing to bowed and dropped joists to give me a level ish structure to support a floor) - the original plan was to use 22mm T & G chipboard (which I loathe but it is a...