I get where you’re coming from about the cement, but honestly, I’m not convinced it’s always the best fix.
Thing is, once that stuff cracks in the cold (which it does, even the “flexible” kind), you’re back to square one. I’ve actually had better luck swapping out the plastic vents for metal, then just using a solid bead of high-grade sealant—less mess, and seems to handle freeze-thaw cycles better. Cement just feels like a band-aid sometimes, especially up north where temps swing hard.“I’d rather scrape off a little extra cement than deal with water stains and mold later.”
Cement just feels like a band-aid sometimes, especially up north where temps swing hard.
I hear you on the cement. Tried it on my shed roof a couple winters back—looked solid at first, but once that deep freeze hit, I noticed hairline cracks by spring. Water found its way in anyway, and I ended up with a soggy patch of insulation. Swapped to metal vents after that, used a polyurethane sealant around the edges, and haven’t had an issue since. The plastic ones just didn’t cut it for me, either. They got brittle and warped after a couple years of sun and cold.
Honestly, the mushroom-style vents seem to work fine if you go with metal and take your time sealing them right. Less maintenance, too. I’m in central Minnesota, so those temp swings are no joke. Cement might be quick, but it’s not worth redoing every year. Just my two cents from messing around with too many shed roofs over the years.
I put in two of those metal mushroom vents last fall, after fighting with condensation all winter before. Here’s what I did: marked the holes, cut with a jigsaw, set the vent in, then used a thick bead of polyurethane sealant under the flange and around the screws. Didn’t bother with cement—just doesn’t hold up here (I’m in northern Wisconsin). No leaks so far, even after a couple freeze-thaw cycles. If you’re on the fence, just double-check your sealant job and you should be good.