Weighing the pros and cons: full roof removal vs. just adding a new layer

Had a similar debate last year on a 12-unit building - flat roof, lots of old patches. The quick fix was tempting (just slap another layer on and hope for the best), but we ended up doing a full tear-off. Messy, noisy, and not cheap, but at least we found some nasty rot before it got worse. If you’re in a wet climate like us, that “sandwich” effect is no joke. I get why folks double up, but I’d rather deal with the pain now than leaks in the middle of January...

If you’re in a wet climate like us, that “sandwich” effect is no joke.

That right there is what gets a lot of folks in trouble. I’ve seen more than a few buildings where they just kept stacking layers and, sure, it looks fine for a while, but underneath? It’s basically a soggy mess waiting to happen. Especially with flat roofs - water just loves to find any little crack and then it’s trapped between layers. Next thing you know, you’re dealing with mold or rot you can’t even see until it’s a real problem.

I get the temptation to go the quick route, though. Tearing off an old roof is loud, messy, and tenants complain about the noise. Plus, the price tag isn’t fun. But in my experience (and I’ve patched up more storm damage than I care to remember), those “sandwich” roofs almost always come back to bite you. The insulation gets soaked, you start getting leaks in weird spots, and good luck finding where the water’s actually getting in.

One thing I’d add - sometimes local codes won’t even let you do a second layer anymore. Depends on where you are, but worth checking before you get too far down that road.

I’ve seen some folks try to save money by just patching the worst spots instead of doing a full tear-off or overlay. Sometimes that buys you a year or two if you’re really strapped for cash, but honestly? If there’s already patchwork all over and you’re seeing signs of water inside, it’s probably time to bite the bullet.

Full tear-off isn’t cheap, but at least you know what’s going on under there. And if you’re in a wet area or somewhere with heavy storms (like us), peace of mind is worth something too. Nothing worse than scrambling around in January trying to find where that drip is coming from...

Curious if anyone’s had luck with those spray-on coatings as a stopgap? I’ve seen mixed results - sometimes they buy time, sometimes they just peel right off after one bad winter.

Had a similar situation last year with a low-slope roof on one of my buildings. We tried a spray-on coating as a temporary fix, but honestly, it didn’t hold up through the first heavy rain - started peeling at the seams. Ended up doing a full tear-off anyway. It was noisy and tenants weren’t thrilled, but at least we finally stopped chasing leaks every time it stormed. Sometimes the headache just isn’t worth the shortcut.

I get where you’re coming from - sometimes the quick fixes just don’t hold up, especially with low-slope roofs. But I’d push back a bit on the idea that all coatings are just temporary bandaids. The trick is making sure you’re using the right type for your roof and climate, and that prep is done right. I’ve seen silicone-based coatings on commercial roofs last years with proper prep - cleaning, priming, and sealing all seams beforehand. If the seams aren’t reinforced or if there’s any moisture trapped, yeah, it’ll peel or bubble.

That said, I totally agree that nothing beats a full tear-off for peace of mind, especially if you’re already chasing leaks. But sometimes adding a new layer (if code allows) can work out, especially if you’re looking to add insulation or reduce landfill waste. I went with a green roof overlay on my own place - took more upfront planning but it’s been solid so far, and the energy savings are noticeable.

Noise is definitely a pain during big jobs though. My tenants still joke about the “roofquake” last spring...

I hear you on the coatings - my neighbor did a silicone one on his flat roof and it’s held up way better than I expected, but he was obsessive about cleaning and sealing every little seam. For me, I went the tear-off route last year because I had a couple of soft spots and didn’t want to risk covering up rot. It was pricier and loud as heck (my dog still freaks out at ladders), but now I don’t worry every time it rains. Did you notice any issues with weight when you added your green roof layer? That’s the one thing that’s kept me from trying it - just not sure my old rafters could handle it.