I’ve seen a lot of roofs where the flashing looked okay from the outside, but water had already crept under and started rusting things out. Once, after a hailstorm, we pulled off some “good” flashing and found rot that had probably been there for years. Inspectors can be a wild card, but honestly, I’d rather just swap it out and know it’s solid—especially with green roofs where drainage is even more critical. It’s not always fun for the budget, but chasing leaks later is worse.
Flashing’s one of those things that’ll bite you if you get complacent. I’ve lost count of how many “fine” flashings I’ve pulled off only to find a science experiment growing underneath. Especially with green roofs—if the drainage isn’t dialed in, water finds every weak spot. I get wanting to save a few bucks, but honestly, swapping out questionable flashing is way cheaper than tearing up a soggy roof deck later. Sometimes it feels like overkill, but it’s saved me headaches more than once.
- Not disagreeing that flashing is critical, but I’ve seen plenty of green roofs where the *real* culprit was poor membrane detailing, not just the metalwork.
- In storm-prone areas (I’m in the Midwest), wind-driven rain finds its way past even “perfect” flashing if the waterproofing layer underneath isn’t continuous or gets punctured during install.
- Sometimes folks focus so much on swapping out old flashing, they miss checking for membrane laps, penetrations, or even fastener holes—those can be just as risky for leaks and rot.
- I get the urge to replace anything questionable, but over-flashing can actually create more seams and potential failure points if it’s not integrated right with the rest of the system.
- On a recent job after a hailstorm, we found water tracking under brand new flashing because someone skipped a primer coat on the membrane—looked fine from above, but moisture still got in.
- For green roofs especially, I’d say:
- Prioritize continuous waterproofing first.
- Use compatible materials (some metals react with certain membranes).
- Make sure drainage mats aren’t blocking scuppers or outlets—seen that cause more ponding than bad flashing ever did.
Not saying don’t replace sketchy flashing, just that it’s one piece of a bigger puzzle. Sometimes it’s what you *don’t* see that causes trouble down the line... especially once plants start growing and hiding everything.
Couldn’t agree more about the hidden issues—membrane detailing is where I’ve seen most green roof headaches start, not just the flashy (pun intended) metal bits. I manage a couple buildings with green roofs here in Chicago, and after our last big storm, we had water sneaking in at a spot that looked “perfect” from the outside. Turned out, someone got lazy with the membrane overlap behind a parapet. Flashing was brand new, but it didn’t matter.
Honestly, I’ve learned the hard way that you can throw all the shiny new flashing you want at a problem, but if the waterproofing layer underneath isn’t continuous, you’re just asking for trouble. And yeah, over-flashing is a real thing—more seams, more places for water to get in, especially if the crew’s in a rush.
One thing I’d add: don’t forget about what’s happening *under* the plants. We had a drainage mat shift during install and block a scupper—took weeks to figure out why water was pooling. Sometimes it’s the stuff you can’t see that’ll drive you nuts later.
Sometimes it’s the stuff you can’t see that’ll drive you nuts later.
That’s the part that gets me every time. I tried to save a few bucks by skipping a full inspection after my install, and sure enough, a year later I had a mystery leak. Ended up being a tiny gap under the soil where the membrane didn’t quite meet up. Lesson learned—cheap now, expensive later.