Finally tackled that metal edging thing on my roof

I get the paranoia, especially with older metal roofs. I’ve managed a few properties with roofs pushing 30 years, and I’ve seen those hybrids used in all sorts of ways - sometimes they hold up, sometimes not so much. The biggest issue I’ve run into is that on older metal, especially if there’s any rust or the paint’s chalked up, the hybrid sealants don’t always bond like they’re supposed to. You might get a good seal for a year or two, but after a couple freeze-thaw cycles, I’ve seen them start to peel at the edges or just turn into this sticky mess that collects dirt and looks awful.

One thing I’ve noticed: if you’re dealing with a roof that’s already got some movement (panels flexing, fasteners loosening), the hybrids seem to struggle more. They’re flexible, but not miracle workers. I’ve had better luck with butyl tape under the flashing, then a bead of hybrid on top - sort of a belt-and-suspenders approach. It’s not pretty, but it’s kept water out longer than just the sealant alone.

Winter’s the real test. Last year, after a brutal cold snap, I checked a spot where we’d used hybrid on an old ridge cap. The sealant was still there, but it had shrunk back from the metal, leaving a tiny gap. Not enough for a flood, but enough to let in wind-driven rain. Had to scrape it out and redo it in the spring. Annoying, but better than a full replacement.

If you’re set on using hybrids, prep is everything. Wire brush, clean with alcohol, make sure it’s bone dry. Even then, I’d plan on checking it every year, especially after a rough winter. I wouldn’t trust it to be “set it and forget it” on anything older than 10-15 years. Newer roofs, maybe, but the old stuff just doesn’t play nice with modern goop.

Curious if anyone’s found a hybrid that actually lasts more than a couple seasons on old metal. I haven’t, but maybe I’m just unlucky...

That’s been my experience too - hybrids just don’t seem to last on old metal, no matter how careful you are with prep. I’ve had better luck layering butyl tape and then a thin bead of sealant, like you mentioned. One thing I’d add: if there’s any hint of rust, I’ll hit it with a rust converter first. Not perfect, but it seems to help the bond a bit. Still, annual touch-ups are pretty much unavoidable on anything over 15 years old in my climate (lots of freeze-thaw). It’s a pain, but beats chasing leaks all winter.

That layering method with butyl tape really does seem to be the most forgiving on older metal, especially when you’re dealing with years of patchwork repairs. I’m with you on the rust converter - skipping that step has bitten me a couple times, especially in spots where water pools up after a thaw. One thing I’ve started doing is lightly sanding the area even after using the converter, just to make sure there’s no loose scale left. Not sure if it’s overkill, but I figure every bit helps.

Annual touch-ups are definitely the norm here too (Midwest winters, so I know the freeze-thaw pain). Sometimes I wonder if it’s worth trying those newer self-leveling sealants, but I’ve had mixed results - the flexibility sounds good in theory, but they seem to peel faster on really old roofs.

Out of curiosity, has anyone tried priming the metal after rust conversion and before the butyl? I keep seeing conflicting advice on whether that helps or just creates another layer for things to fail. Always feels like a balancing act between over-prepping and just getting the job done before the next storm rolls in...

I’ve wondered about the primer step too, especially since every extra product adds to the cost and time. Has anyone noticed if priming actually makes a difference in how long the butyl holds up? I’m always torn between following all the steps and just sticking with what’s worked before. Also, does skipping primer ever cause issues with adhesion, or is it mostly just a peace-of-mind thing? My budget’s tight, so I hate buying stuff that doesn’t really help in the long run.

Has anyone noticed if priming actually makes a difference in how long the butyl holds up?

I’ve done both - primed and unprimed - on different sections over the years. Honestly, on clean metal, I didn’t see a huge difference in adhesion at first, but after a couple seasons, the primed spots looked better. That said, if you’re working with new, clean metal and you’re careful with prep, skipping primer hasn’t bitten me yet. But if there’s any dust or oxidation, primer really does help. I get the budget thing... sometimes it feels like these “extra” steps are just peace of mind, but they can save you hassle down the road.