Been there myself—you're definitely not alone in this. Had a similar scenario about five years back, bought a house with a green roof that turned into a swamp after every rain. The previous owner meant well, but drainage wasn't their strong suit apparently. Before you rip everything out completely though, you might wanna check if you can retrofit a drainage mat underneath. If the structure itself is solid and just lacking slope, sometimes you can carefully remove the vegetation layer, add a proper drainage mat system (something like a dimpled membrane), and then rebuild the growing medium on top. It's not a quick fix, and you'll probably lose a weekend or two, but it's doable.
But honestly, if you're already seeing moldy ceilings and soggy insulation, it might be safer to tear it down and start fresh. Like you said:
"Previous owner had slapped together this DIY green roof without proper slope or drainage layers... total nightmare."
If the DIY job is that sketchy, starting from scratch might be the less stressful route in the long run. Either way, don't get discouraged—once you do it right, green roofs are awesome.
If you're already seeing mold and wet insulation, retrofitting might be too little too late. I'd strip it down, fix the slope issue first, then rebuild properly—otherwise you're just kicking the can down the road... learned that one the hard way myself.
Yeah, mold and wet insulation are definitely red flags... but do you really think retrofitting is always a lost cause? I've seen cases where addressing drainage and ventilation issues carefully can salvage things without a total teardown. Still, you're probably right about the slope—if that's off, you're fighting an uphill battle (literally). Good on you for sharing your experience though; roofing lessons seem to come with a steep learning curve, don't they?
Retrofitting can work, sure, but honestly I've seen it go sideways more often than not. Had a property a few years back where we tried exactly what you're suggesting—addressed drainage, improved ventilation, even put in extra flashing. Looked good on paper, but within a year we were chasing leaks again. Turns out the slope was just subtly off enough to keep water pooling in weird spots. Eventually had to bite the bullet and redo the whole thing anyway.
Not saying it's impossible, just that sometimes the bandaid fixes end up costing more in the long run. If your slope is decent and you catch it early enough, you might get lucky...but from experience, roofs have a way of making their point pretty clearly when they're unhappy.
Yeah, seen this happen plenty. Retrofitting can buy you time, but if the underlying slope or decking is off, you're just delaying the inevitable. I'd double-check slope measurements carefully first—sometimes it's subtle enough to miss at first glance...
