-
I don't think that's what's stopping folks from DIYing it to be fair!
I'd be surprised if it wasn't at least a little part of it — height means scaffolding, scaffolding means other people and timelines, other people and timelines can mean DIY is out of the question
Plus no planning permission or building control required I guess too
slippers-
Of course it's part of it, but you'd still need to learn how to cut and measure beams, assemble a frame, build a durable, insulated watertight roof that won't blow off in a gale, put up stud walls, route services (OK, a GR just needs electric unless it's a palace), apply cladding, insulate it, put down a floor, but the windows in... it's endless. And it has to last decades so don't make a minor mistake that means the whole thing is fucked in seven years of UK weather ok?
No planning, well, kind of. They are generally PD but there's loads of shit you can pull to build something far larger than what PD should allow (which is fuck all) but you need the expertise to pull that off too.
Howard
The skills (and equipment!) needed to do a garden room* properly are the same as doing a loft conversion properly. OK, that might be at height, but I don't think that's what's stopping folks from DIYing it to be fair!
* not a summerhouse, that's just a big shed.