Thoughts on mounting railing posts to the outside of the frame?

I’ve always been a fan of mounting posts to the outside of the rim joist with TimberLOKs or those heavy-duty GRK structural screws. It makes the deck feel rock solid compared to trying to block everything out internally. To clean up the look, I usually just run a cedar fascia board over the rim joist before the posts go on, or I use black hex-head screws that match the balusters. It makes the hardware look like a design choice rather than an afterthought. On the footer situation, 10 inches is definitely a tight squeeze. I learned my lesson on a build last summer when I hit a massive rock and my anchor ended up two inches off center. Now I almost always jump up to 12-inch Sonotubes, even if the load doesn't strictly require it. That extra diameter gives you so much more grace when you're trying to line up your post bases, especially when the heavy clay starts fighting back and your hole isn't perfectly plumb. It’s a bit more concrete to mix, but it saves hours of headache during the framing stage.

I actually prefer mounting posts inside the rim joist every time. When you bolt them to the outside, you’re putting a lot of torque on that single rim joist, and I’ve seen them start to pull away or twist over time, even with structural screws. If you block them in with 2x8s and use through-bolts with oversized washers, that railing isn't going anywhere. It takes more time, sure, but it keeps the lines of the deck much cleaner without having to mess with fascia later.

On the footers, 10 inches in heavy clay is pretty tight. I ussually bump up to 16-inch flared bases like a Bigfoot. In my experience, clay expands and contracts so much with the seasons that a narrow pier can shift or sink if the drainage isn't perfect. Having that extra width gives you a few inches of "forgiveness" when you’re trying to line up your Simpson post bases perfectly with a string line.

As for the balusters, those face-mounted metal ones are fast, but I find they can rattle in high wind. I still prefer the look of 2x2 cedar. If you coat the ends in a wood sealer before installation, they’ll last way longer than people think, and you don't get that industrial look that metal sometimes brings to a backyard.

I'm with ya on those metal balusters. Wood ones are a total time sink and they always warp or rot out way faster than you'd think. It's not just the maintanence—they stay straight, which keeps the whole deck lookin' sharp for years. As for the footers, if you're stuck in heavy clay again, just rent a power auger. It'll kick your teeth in if you hit a big root, but it beats hand-diggin' every time. I'd way rather over-dig a bit than spend all day tryin' to be perfect with a 10-inch hole.

While the structural integrity of exterior-mounted posts is certainly bolstered by the use of modern fasteners, one must meticulously account for the potential for moisture entrapment behind the post, as capillary action can draw water into that interface and lead to premature decay of the rim joist if a proper drainage gap or flashing is not implemented. Regarding your footer diameter concerns, I find that a 12-inch diameter hole is essentially the minimum functional standard for 4x4 or 6x6 posts beacuse it facilitates the use of adjustable standoff bases, wich are indispensable for achieving precise lateral alignment across a sixteen-foot span when your initial excavation inevitably drifts from the string line.

Next time, skip the hand-digging and the 10-inch tubes altogether. I always spec 16-inch Bigfoot Systems footers for clay. That wider bell at the bottom prevents frost heave way better than a straight pillar, and the top gives you a massive landing zone for your Simpson Strong-Tie ABA66 post bases. As for the balusters, you made the right call with the screw-on DeckoRail connectors. I’ve seen 2x2 cedar pickets look like pretzels after two seasons in the sun. If you're worried about the exterior post look, just slap some PostShield sleeves over them. It hides the fasteners and looks way more custom than a bare 4x4.

Quick update—the suggestion about using a cedar fascia to cover the hardware is genius, I’ll definitly do that next time. I am a bit worried about the moisture entrapment and capillary action someone mentioned, though. Do you guys think adding a small spacer between the post and rim joist whould help prevent rot without sacrificing the stability I got from the structural screws?