Just finished my first 8x10 deck — a few observations

I went trough the exact same internal debate about 4x4 posts when I put up my small platform deck three years ago. I ended up sticking with the 4x4s to save some cash, and honestly, for an 8x10 footprint, they’ve stayed perfectly plumb even through some heavy snow loads. You’re right about the look, though; 6x6s have that chunky, high-end feel, but as long as you hit those 48-inch depths, you aren't going to deal with any frost heave issues.

Those metal stringers are a smart move. I tried cutting my own treads for a set of stairs once and messed up the rise and run so badly I had to scrap the whole thing and buy the pre-made steel ones. It saves so much frustration. For the horizontal privacy slats, I found that adding a vertical 2x2 support right in the middle of the run helps prevent the boards from warping over time, expecially if you used cedar or pressure-treated pine. The leveling is always the hardest part. I spent nearly ten hours shimming and adjusting my ledger board becasue my house siding wasn't perfectly square. Keeping the budget under $1500 is impressive; I ended up closer to $2200 once I added the stain and the Camo hidden fasteners.

I acutally ended up ripping out my 4x4 posts after the first winter and swapping them for 6x6s. Even though the math said 4x4s were fine for my 10x12, I couldn't stand the slight vibration every time the dog ran across the boards. The 6x6s provide a much more solid base, expecially when you're bolting thru for the rim joists using those heavy-duty Simpson Strong-Tie SDWS screws. For the stairs, those metal stringers can be a bit of a double-edged sword. I tried the pre-made steel ones from the big box store on my side porch, but they didn't quite line up with my specific grade, leaving me with a weirdly high bottom step. I eventually went back to old-school 2x12 pressure-treated lumber and a framing square. It took more time to cut the notches, but getting that 7-inch rise exactly right across the whole run made the transition to the grass much safer. Horizontal railings look sharp, but keep an eye on the tension over the next year. If you used cedar or green treated wood for those slats, they tend to bow as they dry out in the sun. I had to go back and add vertical blocking every three feet just to keep the lines looking crisp and prevent the gaps from getting uneven.

Spot on about those metal stringers being a lifesaver for the rise and run. One thing people often overlook with those is the transition at the bottom. Since you went 48 inches deep on the posts, I'm assuming you're in a freeze-thaw zone; I found that mounting the base of those metal stringers onto a small concrete landing pad rather than just dirt or gravel keeps the whole assembly from shifting and pulling at your rim joist over time. It really helps keep those thick wooden treads perfectly level year-round.

While 48-inch depths mitigate frost heave, I am curious wether you utilized galvanized post bases or opted for direct burial, as the latter significantly accelerates fungal decay at the grade line regardless of your concrete footing's integrity. Regarding those horizontal privacy slats, ensure you factored in the specific gravity and moisture content of your timber choice, as a lack of adequate gapping between those boards will inevitably lead to buckling when the hygroscopic expansion occurs during the humid summer months. Did you remember to coat the field-cut ends of your pressure-treated lumber with a copper naphthenate solution to maintain the chemical barrier?

Solid price point for that build. Don't sweat the 4x4s too much, they're plenty for an 8x10. I'm more curious about those horizontal slats—did you gap 'em for airflow? I didn't on my first go and they turned into a total sail during a summer storm. Almost took the railing down with it. If they're tight, you might wanna keep an eye on 'em when the wind picks up.

Quick update — the tip about the stringer transition at the bottom was huge, it feels much more secure now. However, I’m definitly noticing that slight vibration someone mentioned when the dog runs across. Since I allready did direct burial for the posts, do you think adding some diagonal bracing between the 4x4s whould help stiffen things up, or is that just a band-aid for not using 6x6s?