Best way to keep critters out without ruining the look?

I ran into the same headache on a 12x20 steel frame project I did using NewTechWood last summer. Instead of lattice, I used black vinyl-coated 1/2-inch hardware cloth. I dug a trench about 10 inches deep around the perimeter and ran the mesh down and then angled it outward in an 'L' shape before backfilling with crushed gravel. It’s been a year and we haven't seen a single groundhog or stray cat under there.

For the look, I fastened vertical composite fascia strips over the mesh, leaving a 3/4-inch gap between each slat. It matches the modern vibe of the steel tubes and keeps the airflow moving so the underside doesn't get swampy. I used #10 self-drilling Tek screws to attach the slats directly to the 2x6 perimeter. Just make sure you don't skip the gravel over the buried mesh; it realy helps with drainage and stops things from digging right at the edge.

Honestly, I’d reconsider burying mesh against a steel frame. Even with drainage holes, trapping damp soil and organic debris right against those screw piles is a recipe for accelerated corrosion over the next decade. I tried the hardware cloth method on a similar build with Fortress Evolution framing, and within two seasons, the trench just turned into a compost bin for wet leaves that never dried out. I went with a heavy-gauge aluminum slat system instead. I used 1x3 black aluminum tubes spaced about 3/4 of an inch apart, mounted vertically. It gives that clean, architectural look that matches the 2x6 perimeter perfectly. Because there’s a gap at the bottom just above a bed of 3-inch river rock, air flows freely under the joists. Animals hate the noise of the rocks shifting if they try to dig, and you aren't creating a moisture trap against your steel. Since you're already tapping machine screws into the frame, it’s easy to bolt on some small L-brackets to hold the slats. It’s a bit more work than a mesh trench, but it’ll save your frame and look a lot more intentional than buried wire.

That steel frame sounds absolutely beastly! I'm just getting started with my first DIY deck and seeing a 16x24 build is making me so hyped to get my hands dirty. Since you mentioned tapping machine screws into those 2x6 tubes, do you need a heavy-duty drill or some kind of special lubricant for the bits? I'm terrified of snapping a tap halfway thru a joist and ruining the whole look! Also, are you guys finding that the hidden clips work okay with the steel expansion, or do they tend to rattle after a summer of heat?

Spot on with the L-shaped mesh and gravel combo. It’s the only way to stop those persistent skunks from digging. I'd just suggest one more thing: use stainless steel zip ties or heavy-duty clips to secure that hardware cloth to your screw piles before you backfill.

If you use standard galvanized ties, they’ll snap from the soil acidity way before the vinyl-coated mesh does. Keeping that mesh tight against the piles ensures there are zero gaps for mice to squeeze trough where the frame meets the foundation.