Copper mesh is definitely the way to go for long-term mouse proofing, especially in damp climates. I used to rely on steel wool too, but after a couple of rainy seasons here, it just crumbled away and the mice were right back at it. The upfront cost of copper stings a bit, but I haven’t had to redo any of those spots in years, so it’s paid off.
On shims, composite ones have made a big difference for me. I tried using pine for a while—mainly because it was cheap and easy to cut—but like you said, it compressed over time, especially when my place got humid in the summer. That threw my window alignment out of whack and I ended up having to re-level a couple of them. With composite, I just cut to size, pop them in, and forget about them. No swelling, no splitting.
One thing I’d add—if you’re working off-grid and don’t want to haul a bunch of stuff in, pre-cutting your copper mesh and composite shims before you head out saves a lot of hassle. Learned that the hard way after a few too many trips back to the truck...
I hear you on copper mesh—it’s got a lot going for it, especially if you’re dealing with persistent critters. I do want to throw out there, though, that I’ve had some luck with stainless steel mesh in certain spots. It’s not as foolproof as copper in the long run (and it’ll rust if you get standing water), but if you’re working with a tight budget or just need a quick fix until you can get back out there with better materials, it’s held up surprisingly well for me—at least for a season or two. Sometimes those little wins keep the project moving.
On the shims, composite is definitely easier than fussing around with warped wood when it gets humid. That said, I ran into an issue last fall where my composite shims actually slipped a bit because they were so smooth—especially in a spot where the window frame wasn’t perfectly square. Ended up wedging in some leftover cedar shims alongside them just to keep everything locked in place. Not ideal, but sometimes you’ve just gotta work with what you’ve got on hand. If I had to do it again, I’d probably rough up the surface of the composite ones or use some adhesive.
And yeah, pre-cutting everything before heading off-grid does save time, but I always seem to forget something or mis-measure at least one spot. Now I just toss an extra small handsaw and utility knife in my bag—adds a pound or two, but worth it for peace of mind when I’m 40 minutes from the nearest hardware store.
Funny how these little details end up mattering more than the big stuff sometimes...