Okay, you've raised some important points regarding bonding requirements for your hot tub installation under the pergola. Let's break it down

Key Considerations:
Pergola Posts (Metal)

You are correct, these will require bonding if they are within the defined zone (typically 5 feet horizontally from the inside wall of the hot tub and 12 feet vertically).

Hot Tub Rim Height

You are also correct about the 28" exception in 680.42(B). This is your first line of defense. If the rim of the hot tub is going to be 28" or more above the surrounding surface, you likely won't have to bond the surrounding surface at all.

Pergola Flooring (Vinyl/PVC)

This is your primary question. Since it's non-conductive, you cannot bond it directly. The purpose of bonding is to create an equipotential plane (equal potential) to minimize the risk of shock. You can't bond something that doesn't conduct electricity.

The Slab

The concrete slab is the "perimeter surface" so that's where the height of the rim of the hot tub must be measured from.

Here's how to approach the situation


Determine the Final Height - Before Concrete Pour



Critical Step

Before the concrete is poured, absolutely determine the final height of the hot tub rim relative to the finished concrete slab height. Get the manufacturer's specifications for the hot tub's installed height, including any support structure it sits on. Coordinate with the client and concrete contractor to ensure the final slab height is planned to achieve that 28" clearance, if possible. This is the simplest and most cost-effective solution.2.

If 28" Clearance is Achieved

If you can achieve the 28" height requirement, you're in good shape. You'll still need to bond the metal pergola posts if they are within the defined zone.3.

If 28" Clearance Cannot Be Achieved

This is where it gets more complicated.

Focus on the Zone

Consider the area within the bonding zone (the 5-foot/12-foot mentioned previously).

No Bonding to Non-Conductive Flooring

Again, do not attempt to bond the vinyl/PVC flooring. It won't work, and it's not the correct approach.

Alternative Grounding

If the pergola posts fall within the required equipotential bonding distance as described in 680.26, they must be bonded to the hot tub grounding system with a solid copper conductor, sized as required by the NEC.

Important Considerations



Inspection

Clearly document your reasoning and measurements for the inspector. Be prepared to explain why you're not bonding the vinyl/PVC and why you're relying on the 28" height exception (if applicable) or other grounding measures.

Manufacturer's Instructions

Always follow the hot tub manufacturer's installation instructions. They may have specific bonding requirements that exceed the NEC minimums.

Local Codes

Be aware of local amendments to the NEC. Some jurisdictions may have stricter bonding requirements.

In Summary:

Your best approach is to plan the concrete pour to achieve the 28" height requirement and that removes the requirement to provide equipotential bonding of the perimeter surface around the hot tub. Bond the metal posts to the hot tub grounding system. Do not attempt to bond the non-conductive vinyl/PVC flooring. Communicate clearly with the client, the concrete contractor, and the inspector to ensure a safe and code-compliant installation. Flag for review