"Ended up adding some silica gel packs in strategic spots and a small battery-powered fan to circulate air occasionally."
Totally agree about the silica gel packs—they're underrated. Curious though, did you consider using a moisture barrier under the shelter's floor slab? When we prepped ours, we added a thick polyethylene sheet before pouring concrete. It wasn't expensive and seems to have helped reduce condensation issues significantly. Still get some dampness after major storms, but nothing too annoying...yet. Did anyone else try something similar?
We went with silica packs too, and honestly they've been doing alright. I thought about a moisture barrier briefly, but we were in a rush to pour the slab before the rainy season hit, so it slipped my mind. Kinda regret that now, haha. Right after heavy rains, we notice a bit of dampness on the walls—nothing crazy, but enough to make me wonder if polyethylene would've been worth the extra step. A friend of mine swears by sealing the concrete itself with one of those penetrating sealers. Said it cut down moisture dramatically in his basement. Might give that a shot if things get worse, but for now the silica and a small rechargeable fan seem to do the trick pretty well.
"Right after heavy rains, we notice a bit of dampness on the walls—nothing crazy, but enough to make me wonder if polyethylene would've been worth the extra step."
Honestly, polyethylene barriers can help quite a bit, but they're not always foolproof. I've seen cases where moisture still finds its way in through tiny gaps or seams. Your friend's suggestion about penetrating sealers is actually pretty solid advice. They chemically bond with the concrete, making it harder for moisture to seep through. Might be worth trying down the road if the silica packs and fan combo starts struggling...
Have you checked your drainage setup outside? Sometimes tweaking the grading or adding a rain garden nearby can cut down moisture issues inside...might be easier (and greener) than sealing everything up chemically.
Totally agree on the drainage angle—good call. One thing I'd add: make sure your downspouts actually direct water away from the shelter. I had mine dumping too close at first...just extending them a few feet made a noticeable difference inside.
