I’ve seen a few green roof patches on low-slope sheds, but I always wondered about drainage and weight over time. Did you have to reinforce the structure at all, or did it just sit right on top? I’d be worried about moisture getting trapped underneath, especially in wetter climates.
I’d be worried about moisture getting trapped underneath, especially in wetter climates.
That’s a legit concern. I helped my uncle put a green roof on his old garden shed last spring, and we definitely had to think about drainage and weight. His shed was already pretty sturdy, but we still added a couple of extra joists just to be safe. The soil and plants aren’t light, especially after a good rain—honestly, it surprised me how much heavier it got.
As for moisture, we used a waterproof membrane under everything, then put down a layer of gravel before the soil mix. That seemed to help with drainage, but I still check on it every few weeks. He lives in the Pacific Northwest where it rains all the time, so I get what you mean about water getting trapped. So far, no leaks or rot underneath (fingers crossed), but I’ve heard stories from folks who skipped the membrane and ended up with moldy plywood after a season or two.
If you’re thinking about doing something similar, I’d say don’t skimp on the prep work. It’s tempting to just throw some dirt and sedum up there and call it good, but that’s when problems start creeping in. And yeah, tarps are fine for an emergency leak fix—I’ve used them myself—but they’re not gonna hold up long-term if water keeps pooling underneath.
It’s kind of wild how much planning goes into even small green roofs. Not sure I’d trust one on anything bigger than a shed unless you really know what you’re doing... or have deep pockets for reinforcements. But when it works out, they look awesome and keep things cooler inside during summer. Just gotta stay on top of maintenance—or at least keep an eye out for soggy corners!
Tarping definitely works as a quick fix, but I’d never trust it for more than a few weeks—especially in a rainy climate. I had to tarp my garage roof after a storm last fall. Used a heavy-duty 12-mil tarp, secured it with 2x4s screwed right into the rafters, and weighted the edges with bricks. It kept the water out for about a month, but after a couple of big windstorms, it started to shift and water found its way underneath. The plywood underneath was damp but not rotten yet, so I got lucky.
One thing I’ve noticed is that tarps don’t breathe at all. If there’s any moisture already in the roof deck or attic, it just sits there and can start to grow mold. In my case, I propped the tarp up a bit in the middle to let water run off, but you still get condensation underneath when the temps swing. Not ideal if you’re dealing with an older roof or questionable decking.
For anything longer than a few days or a week, I’d go with a peel-and-stick underlayment as a temporary patch, especially over plywood. It sticks better, seals around nails, and doesn’t trap moisture quite as badly. Costs more than a tarp, but it buys you time until you can get a real repair done.
I get why people use tarps—they’re cheap and fast—but they’re really just buying you time. If you leave one up too long, you might be looking at replacing decking or even rafters, depending on how much water sneaks in. And yeah, like you said, if water pools anywhere, it’ll find its way through eventually.
Green roofs are a whole different beast. I’ve never built one myself, but I’ve helped friends plan them. The drainage layers and membranes make all the difference—just like with a regular roof, moisture management is everything. If you skip steps or try to save money on materials, you’ll pay for it later.
Long story short: tarp if you have to, but don’t wait too long to get a proper fix. And if you’re in a wet area, check under that tarp every few days for soft spots or mold. It’s amazing how fast things can go sideways when water gets involved...
I get the concern about tarps trapping moisture, but honestly, peel-and-stick underlayment isn’t always in the budget, especially if you’re dealing with a big area.
For me, a $30 tarp kept things dry through two months of rain—wasn’t perfect, but it beat letting water pour in. Just gotta check under it now and then. Sometimes cheap and fast is all you can do.“Costs more than a tarp, but it buys you time until you can get a real repair done.”
I get being on a budget—my roof’s got a weird pitch and just getting a quote for underlayment nearly made me choke. I did the tarp thing too, but I noticed mold starting after a few weeks. Maybe it’s my humid area (southeast), but now I’m paranoid about what’s going on under there. Still, like you said, sometimes it’s all you can do short-term. Just wish there was a cheap fix that didn’t have trade-offs...