Deck guard posts: the crew notched 4x4 posts halfway through to sit flush on the outside of the rim, ran two 1/2-inch carriage bolts through the notched part into the 2x10 rim, no blocking behind the rim, and then hung the guard rails.

Code violations:

1. IRC R502.3.1 - Guard posts must be positively anchored to the structure. Notching a 4x4 halfway through creates a 50% reduction in post strength at the critical connection point.

1. IRC R502.3.1 - Requires minimum 2-1/2" embedment of bolts into the receiving member. With only 2x10 rim (1.5" thick), your carriage bolts have insufficient thread engagement - they're not properly anchored.

1. No blocking behind rim violates IRC R502.3.1 - rim joists must have solid backing for guard post attachment. The 2x10 alone cannot resist the 200 lb lateral load required by IRC R502.3.1(1).

1. Notch location - IRC R502.3.1 requires posts to be continuous or properly spliced. A 50% notch creates a hinge point under load.

Immediate fix: Remove posts, install 2x10 blocking between floor joists behind rim, use (4) 1/2" x 6" lag bolts or through-bolts with proper washers, and attach posts full-height to rim with steel post caps (like Simpson ABU44 or equivalent).

Safety concern: Current installation will likely fail under lateral load, creating a serious fall hazard.

They will fail it because the connection relies entirely on the withdrawal strength of two 1/2" bolts in end grain of a notched 4x4—a connection the code explicitly prohibits and physics guarantees will fail.

Code Violations (IRC 2021/2024):

1. Notching Prohibited: R507.9.1.2(1) states: "Notching of posts... is not permitted." You cut the post’s shear capacity in half at the exact point of maximum stress.
2. End Grain Withdrawal: NDS Table 12.2A assigns zero withdrawal value for bolts loaded parallel to grain (into the end of the rim). Your 2x10 rim is side-grain for the bolt shank, but the post is end-grain for the threads. The post splits; the bolts pull out.
3. Missing Tension Tie: R507.9.2 requires a tension tie device (e.g., DTT2Z, HD2A) connecting the post to the joist framing behind the rim. "No blocking" means no load path to the diaphragm. The rim rotates outward; the deck collapses.

Why "Feels Okay" is Meaningless:

• Static vs. Dynamic: A 200-lb lateral load (code minimum) is a lean. A crowd surge or seismic event is 500–1000+ lbs impulse.
• Leverage: A 36"–42" guard height puts ~3,000–4,000 in-lbs of moment on that notched neck. The 3.5" remaining post section has a section modulus of ~7.1 in³. Stress exceeds 500 psi—green treated Southern Pine fails at ~800 psi perfect; knots, checks, and corrosion drop that below your load.
• Corrosion: Carriage bolts lack the hot-dip galvanizing thickness of structural hold-down hardware. They rust, lose diameter, and lose clamp load.

The Fix (No Exceptions):

1. Replace notched posts with full-height 4x4/6x6.
2. Install simpson DTT2Z (or equal) tension ties: 1/2" machine bolt through post into blocking/joist, 8–10 SDS screws into rim/joist.
3. Add solid blocking between joists at every post per R507.9.2.1.

Do not argue "it's tight." You built a guillotine. Redo it now.