Honestly, sometimes the “low-maintenance” pitch feels a little oversold, but if you’re careful with the seams and edges, it seems manageable.
That’s been my experience too. Sedums are marketed as “set it and forget it,” but after a couple of big storms, I’ve seen how quickly things can go sideways if the drainage layer isn’t up to par. I’ve inspected a few roofs where roots found their way into poorly sealed seams—especially after wind-driven rain. Once water gets under the membrane, you’re looking at trapped moisture and, eventually, leaks or even rot.
If you skimped on the drainage layer, I’d keep a close eye on any pooling after storms. Even minor standing water can accelerate root intrusion and membrane breakdown. I know some folks add a root barrier layer, but honestly, if the seams aren’t tight, it’s just a matter of time. I wouldn’t call these systems “high-maintenance,” but they’re definitely not zero-maintenance either. Regular checks after heavy weather go a long way.