That’s pretty much where I landed, too. I kept thinking about how much easier (and cheaper) it’d be to just slap another layer on, but then I started poking around and found some soft spots near the vent stack. Made me nervous about what I’d be hiding under there. Plus, my neighbor did an overlay a few years back and now he’s dealing with sagging rafters—definitely not worth the short-term savings in my book. Full tear-off hurt the wallet, but at least now I know what’s up there and don’t have to stress every time it rains.
We ended up doing a full tear-off last year after finding some moisture under the old shingles. I get why people go for the overlay—saves cash up front and seems less hassle—but once I saw the state of the decking in spots, it was a no-brainer. If there’s already soft wood, another layer just hides trouble and adds weight. Cost stung, but peace of mind is worth it, especially in a place like ours where we get heavy spring storms.
I get the peace of mind thing, but I’ll admit I went the overlay route on my garage roof last year. Decking was still solid, and honestly, I just didn’t have the budget (or the patience) for a full tear-off. I checked for soft spots with a broom handle—highly scientific, I know—and patched a couple minor areas before adding the new layer. Not saying it’s perfect, but for a low-traffic, low-leak zone, it’s held up fine through two Midwest winters. Sometimes “good enough” really is good enough... at least until I win the lottery.
I see this a lot, especially on detached garages or sheds. If the decking’s solid and you’re not stacking up layers, overlays can buy you time. I’d just keep an eye out for trapped moisture—sometimes it sneaks in under that second layer and causes headaches down the line.
