Yeah, those code limits on overlays can really catch people off guard, especially when older homes have been through a few rounds of patchwork. Around here, inspectors are strict—two layers max, and anything beyond that’s an instant red flag for insurance. I’ve seen cases where folks tried to sneak in a third layer to save on tear-off costs, but it always comes back to bite them during storm season. You’re right about attic airflow too—if you’re stacking layers, ventilation gets even trickier. Good call paying attention to what’s under the shingles.
I’ve seen cases where folks tried to sneak in a third layer to save on tear-off costs, but it always comes back to bite them during storm season.
It’s wild how often people underestimate the weight factor, too. Three layers of shingles on an old frame? That’s just begging for sagging rafters or worse, especially after a wet winter. I get the temptation to skip the tear-off—less mess, less labor—but you’re just hiding potential rot or soft spots. Plus, like you said, ventilation gets choked off. I’ve crawled through attics that felt like saunas because of this. Sometimes “saving money” up front just means bigger headaches later.
The ventilation issue gets overlooked way too often, especially with multiple layers. I’ve seen moisture get trapped between old and new shingles, and before you know it, there’s mold or even deck rot. Curious if anyone’s had luck with those newer “breathable” synthetic underlayments in a re-roof situation? I’m skeptical they’d make much difference if the layers are already stacked up, but maybe I’m missing something.
I hear you on the ventilation—my last house had two layers and we ended up with a soft spot near the ridge from trapped moisture. I’ve wondered about those synthetic underlayments too, but honestly, if the old shingles are still there, can anything really breathe? Maybe it helps a little, but I’m not convinced it solves the core problem. Anyone actually notice a difference in their attic temps or humidity after using them?
if the old shingles are still there, can anything really breathe? Maybe it helps a little, but I’m not convinced it solves the core problem.
You’re spot on—layering shingles just doesn’t let things dry out the way folks hope. I’ve seen a few attics where synthetic underlayment was used over old shingles, and honestly, the difference in humidity or temp was pretty minimal. The real game changer is always better ventilation or a full tear-off. It’s tempting to save money with a second layer, but those soft spots and trapped moisture can sneak up on you... happened to my neighbor last year, and he’s still dealing with the aftermath.
