NEED ADVICE ON REPLACING AN OLD LEAKY ROOF
Extra taping is one of those things that feels like overkill until you see what happens without it—frost, mold, the whole mess. I get the urge to over-seal, but there’s a fine line before you start trapping moisture where you really don’t want it. As for rigid board in old homes, I’ve wrestled with it in some pretty funky eaves and honestly, it’s not always worth the headache. Sometimes a good dense-pack cellulose or even mineral wool fits those odd angles better, and you don’t end up cursing at 2am trying to cut foam to fit a 120-year-old roofline. Just my two cents...
Sometimes a good dense-pack cellulose or even mineral wool fits those odd angles better, and you don’t end up cursing at 2am trying to cut foam to fit a 120-year-old roofline.
That’s the truth—old houses never have a straight line where you want one. I’ve found mineral wool especially forgiving in those weird nooks, plus it doesn’t mind a bit of moisture if you miss a spot with the vapor barrier. One thing I’d add: don’t skimp on air sealing around penetrations (chimneys, vent pipes, etc). Even if you’re not going crazy with tape everywhere, a little attention there pays off.
On over-sealing, I do think there’s such a thing as too much. Once, I went heavy-handed with poly and tape in an attic, and ended up with condensation issues—had to pull it all back and redo with a smart membrane. Now I always double-check that the assembly can dry in at least one direction.
If you’re replacing the whole roof, it’s tempting to modernize everything, but sometimes matching the old materials (like using skip sheathing with wood shingles) actually keeps things drier long-term. Just depends on what you’re working with...
Now I always double-check that the assembly can dry in at least one direction.
That’s key. I once worked on a Queen Anne with a complicated roofline—mineral wool was a lifesaver for those impossible angles, but the real headache was sealing around all the oddball vent stacks. Skipped the poly that time and used a vapor-smart membrane, which kept things from getting soggy. Matching old skip sheathing is smart, but sometimes you just have to pick your battles depending on how much rot you’re dealing with under there...
Matching old skip sheathing is smart, but sometimes you just have to pick your battles depending on how much rot you’re dealing with under there...
Yeah, that’s the truth. I’ve seen folks get hung up on making everything look original, but if half the rafters are mush, you’re just asking for trouble down the line. Vapor-smart membranes are a solid call—poly always makes me nervous, especially in these older places where nothing’s square and air leaks are everywhere. I’ve had mixed luck with mineral wool myself, but it’s definitely easier to work into weird corners than rigid foam.
Sealing around vent stacks is always a pain. I swear, whoever designed some of these old roofs must’ve hated future roofers. Sometimes you just have to accept a little compromise for the sake of actually getting it watertight and not spending weeks chasing every last detail. Sounds like you made the right calls given what you were up against.
Vapor-smart membranes are a solid call—poly always makes me nervous, especially in these older places where nothing’s square and air leaks are everywhere.
That’s exactly what I’m worried about with our place. Every time I pull up a board, I find another spot that looks like it was patched by someone’s granddad in the '60s. Did you insulate right up to the sheathing, or leave an air gap? I keep reading conflicting advice and don’t want to trap moisture by accident...