Purlin in loft

Just need a second opinion from a builder please....i'm looking to make more space in my loft for storage. I don't want a full blown loft conversion/room. Builder has suggested taking out the A-line posts and putting in a purlin across the roof. (I think he said they would be supported down to the floor though).
Just wondering if that's the right way to go about it?.....Do I need building regs?....(just read I need them to fit a new boiler - which I did, and didn't get regs, just booked a plumber!).