Tesla V3/V4 Supercharger Pad: Concrete Spec Guide

Quick answer: The working concrete spec for an 8-stall Tesla V3 or V4 Supercharger pad in NC is an 8-inch slab on 8 inches of compacted ABC stone, #4 rebar at 12 inches on center each way, two 2-inch PVC conduit stubs per stall for the 1,000 VDC feeder plus one 1-inch conduit for communications, a separately poured 10-inch PSA cabinet pad with #5 rebar at 10 inches on center, a bonded ground ring with two 8-foot ground rods per PSA cabinet tied into the rebar mat, and a 4,500 PSI air-entrained mix that reaches equipment-install strength in 7 days and full 28-day strength before the site goes live. Turnkey NC pricing runs $8,500 to $16,000 per stall for the concrete work only. The stub-out geometry, the anchor-bolt pull-out capacity, and the ground-resistance test are the three items that pass or fail the Tesla site-acceptance walk — everything else is downstream of getting those right at the pour.

V3 vs V4 pad footprint: what changes and what does not

The concrete pad scope for a Tesla Supercharger has shifted meaningfully between the V3 (Superchargerv3) architecture that dominated 2019 through 2023 and the V4 architecture that is standard on new builds from mid-2024 forward. The stall bay itself has not changed much — 10 feet wide by 18 to 20 feet long, aligned to standard parking-bay geometry, with wheel stops at the head of the stall and the stall connector reaching from the passenger-side rear quarter of the parked vehicle.

What has changed is the cabinet architecture. V3 sites use a per-stall charging cabinet — one cabinet, one stall, with the cabinet set on a small footprint pad immediately behind the wheel stop. V4 sites use a Power Sharing Architecture (PSA) cabinet that consolidates power for 4 to 8 stalls into a single shared cabinet set at the head of the stall row. The PSA cabinet is bigger, heavier, and carries more anchor-bolt loading than the per-stall V3 cabinet — 4,000 to 6,000 pounds fully loaded, with anchor-bolt pull-out tension rated at 12,000 pounds sustained per Tesla's site-acceptance criteria. The concrete work under the cabinet is scoped separately from the stall bay pours and gets its own thickness and reinforcement spec.

Electrify America, EVgo, and ChargePoint DC fast-charger sites follow the same concrete pattern with different vendor-specific cabinet dimensions and anchor patterns. The stall-bay pour is essentially identical scope; the cabinet pad geometry is vendor-specific and comes off the design package.

8-inch slab, #4 rebar at 12 inches: the stall-bay working spec

The honest working spec for the Supercharger stall bay is an 8-inch slab on 8 inches of compacted ABC stone, reinforced with #4 rebar (0.500-inch diameter) at 12 inches on center each way. The load profile on the stall is not extreme relative to the commercial floor scopes we cover in our forklift-rated warehouse floor guide — passenger EVs weigh 4,000 to 6,500 pounds curb weight and pull in on rubber tires — but the slab has to carry three loads that a parking-lot slab does not: the cable-management arm loads that reach across the stall, the anchor-bolt tension pattern from the stall connector post, and the freeze-thaw cycling that will crack a thinner slab within 3 to 5 years in Piedmont NC winters.

The 8-inch slab clears all three of those loads. Below that thickness — the 4- to 6-inch parking-lot default — the slab will settle at the anchor-bolt corners within 12 to 24 months, crack around the stall connector post base, and start failing the equipment-alignment tolerance that Tesla's monthly site-quality audits check for. The rebar spec matters as much as the thickness: welded wire fabric fails to hold cracks tight under the anchor-bolt tension and the freeze-thaw cycling, and the crack widths open above the 1/8-inch threshold that starts feeding water into the substrate.

Subgrade compaction to 95 percent modified Proctor across the 8-inch ABC base is the line item that separates a real Supercharger pad from a shortcut pour. Inadequate compaction is the failure mode that shows up 18 to 30 months after commissioning — the slab settles non-uniformly under the cable-management arm loading, the stall connector post drifts out of alignment tolerance, and the site fails the next quality audit.

PSA cabinet pad: 10-inch slab, #5 rebar, 12,000-pound anchor pull-out

The V4 PSA cabinet pad is a separately poured, more heavily reinforced slab set at the head of the stall row. The working spec is a 10-inch slab minimum on 10 inches of compacted ABC stone, reinforced with #5 rebar (0.625-inch diameter) at 10 inches on center each way, poured 4 to 6 inches above finished grade so the cabinet base plate stays out of standing water. The anchor-bolt pattern is set into the rebar cage before the pour, with the anchor bolts pre-positioned to the cabinet base plate template supplied in the Tesla design package.

The anchor-bolt pull-out capacity has to test at 12,000 pounds sustained per Tesla's site-acceptance criteria. That test is run at commissioning with a hydraulic pull-tester on each anchor bolt — the concrete cannot pull out, the bolt cannot yield, and the epoxy-set bolts (if used) cannot debond. Meeting the 12,000-pound target on cast-in-place anchor bolts requires the 10-inch slab with the tight rebar spacing plus properly consolidated concrete at 4,500 PSI minimum. Undersizing any of those three items — thinner slab, wider rebar spacing, lower PSI mix — is a failed pull-out test and a $8,000 to $25,000 rework per cabinet.

Conduit pre-set: two 2-inch DC + one 1-inch comms per stall

The conduit pre-set is where most Supercharger pad pours fail their site-acceptance survey. The stubs land 2 to 6 inches off the required position, the sweep radius is too tight, or the stub height is wrong for the equipment cabinet — and the electrician has to core-drill and re-run instead of connecting straight in. The pre-pour geometry work is the make-or-break line item.

The working sequence: (1) pull the Tesla site design package and pin the exact stub-out location, spacing, and stub height for each conduit before rebar tie-in. Use laser layout for the geometry, not a tape measure. (2) Set two 2-inch schedule 40 PVC conduits per stall for the 1,000 VDC feeder from the PSA cabinet to the stall connector — stub height typically 4 to 6 inches above the finished pad, sweep radius 24 inches minimum. (3) Set one 1-inch schedule 40 PVC conduit per stall for the communications and monitoring cables — same stub height, tighter sweep radius acceptable at 12 inches. (4) Strap the stubs to the rebar mat with two-strap ties at the sweep and at the stub top so nothing moves during the pour. (5) Cap the stub tops with rated end-caps to prevent concrete intrusion. (6) Photograph and dimensioned-verify every stub position against the design package before the pour releases.

The pre-pour verification photograph is the audit trail that saves the site if the survey catches a stub 3 inches off — Tesla accepts a pre-pour verified photograph as evidence of good-faith construction, and the workaround is usually a shorter cable pigtail off the cabinet instead of a saw-cut concrete rework. The same pre-pour verification discipline we apply on residential work in our final-payment inspection checklist applies scaled up: document before you pour, not after.

Grounding: bonded ring, supplemental rods, rebar tie-in

Grounding for a Supercharger installation is more than the equipment ground bond — the site needs a bonded ground ring around the PSA cabinet pad, supplemental ground rods driven at the cabinet corners, and the rebar mat in the concrete tied into the ground ring as a supplementary ground electrode. This is the code path Tesla's design package specifies, and it is more work than a standard 480V panel install.

The working spec: (1) two 8-foot copper-clad steel ground rods driven at the front-left and front-right corners of the PSA cabinet pad, cad-welded to a #6 bare copper ground conductor that rings the pad perimeter. (2) The rebar mat in the pad bonded to the ground ring at four points with #6 bare copper cad-welded jumpers — this makes the rebar a supplementary ground electrode per NEC 250.52(A)(3). (3) The equipment grounding conductor from the PSA cabinet frame bonded to the ground ring at the cabinet ground lug. (4) A ground-resistance test at commissioning that reads below 25 ohms per NEC 250.53(A)(2). Most NC Piedmont soils read 40 to 80 ohms on a single rod, which is why the ring-and-rebar path is required rather than a single ground electrode.

The bonded rebar mat has to be planned before the rebar tie-in, not after. Dropping a cad-weld connection into cured concrete is not the path — the concrete has to break, the connection has to core, and the whole thing has to re-pour. The rebar mat, the ground ring, and the cad-weld points get spec'd on the shop drawing and installed together as one operation.

4,500 PSI air-entrained mix and 7-day equipment install

The concrete mix for a Supercharger pad is 4,500 PSI compressive strength minimum, air-entrained at 5 to 7 percent for NC freeze-thaw exposure, with a water-to-cement ratio capped at 0.45 to limit drying shrinkage. The same low-shrinkage discipline we specify for data-center floors applies scaled to Supercharger scope — a shrinkage-reducing admixture in the mix is the difference between a pad that hits FF spec at the anchor-bolt corners and a pad that cracks around the cabinet within a year.

The cure schedule matters as much as the mix. The pad reaches 3,000 PSI at 3 days, 4,500 PSI at 7 days, and full 28-day strength at 28 days. Tesla and the third-party site-integration contractor can install the PSA cabinet and stall connector posts at the 7-day mark once the pad clears 4,500 PSI on cylinder break tests, but the site cannot go live for public charging until the pad clears the 28-day cure and the ground-resistance test passes. The cure-blanket schedule follows ACI 308R — moist cure for 7 days at 50 to 90 degrees ambient, protection against freezing for the first 24 hours below 40 degrees ambient. Skipping cure protection to speed up the equipment-install schedule is a failed pull-out test at day 30, not a saved week.

NC market notes

Three regional patterns shape Supercharger and DC fast-charger pad work across the state.

The Charlotte / Concord I-85 corridor. Highest density of Tesla Supercharger stalls in the Carolinas, with hub sites at Concord Mills, the Rock Hill overflow, and I-85 corridor pull-offs carrying Atlanta-to-Richmond traffic. Site developers in this corridor spec V4 PSA architecture on all new builds and V3-to-V4 retrofits on the older stations. Cabarrus and Mecklenburg engineering reviews run 5 to 10 business days for EV site-permit packages. Carolina Sunrock and Vulcan both carry the 4,500 PSI air-entrained mix at the volume required for the Concord Mills-scale sites.

The RTP / I-40 corridor. Business-travel and commuter-oriented charging at Brier Creek, Cary Crossroads, and RTP-adjacent hubs. Wake and Durham county EV permit packages run 7 to 14 business days. Site pours in this corridor tend to run smaller (4 to 8 stalls) and integrate with existing shopping-center or office-park parking lots — which means saw-cut, tearout, and re-integration to the existing lot grading is scope that a bare-lot Concord Mills-style build does not carry.

The I-77 mountain-approach corridor. Hickory, Statesville, Mooresville hub sites carry Charlotte-to-Asheville and Blue Ridge tourist charging demand. Iredell and Catawba county permit review runs 5 to 10 business days. The mountain approach carries more freeze-thaw cycling than the Piedmont sites — up to 60 freeze-thaw cycles per winter in the Hickory-to-Statesville band versus 25 to 35 in Charlotte — so the air-entrainment spec runs at the top of the 5-to-7 percent range and cure protection extends through the first 72 hours below 40 degrees ambient.

Frequently asked questions

How long from mobilization to Supercharger site live?

Turnkey concrete scope on an 8-stall bare-lot Supercharger build runs 3 to 5 weeks. Site prep, subgrade, and pour take 5 to 10 working days. Cure to 4,500 PSI takes 7 days. Equipment install runs 3 to 5 days from Tesla or the site-integration contractor. Ground-resistance test, commissioning, and site-acceptance walk take another 3 to 5 days. Total 21 to 35 days from mobilization to public charging live.

Can we pour in winter?

Yes, with cold-weather protection. Cure blankets, insulated forms, and temperature monitoring per ACI 306R keep the pour clearing the strength targets through NC winter ambient. Ambient below 40 degrees requires accelerator in the mix (calcium chloride not permitted around embedded copper conductors — use non-chloride accelerator) and 72-hour cure protection minimum. Ambient below 20 degrees requires heated enclosures.

What if the site is a build-in-existing-parking-lot?

Saw-cut the existing asphalt or concrete to the required pad footprint, tearout to subgrade, replace with 8 inches ABC stone, pour the new pad flush to the surrounding lot grade, re-integrate the drainage grade at the pad edges. Scope adds $12 to $22 per SF for tearout and grade re-integration on top of the pad pour pricing.

Do we need a stormwater permit for the pad?

Sites under 1 acre of disturbed area typically clear NC stormwater at the local municipal level with a simple erosion-control plan. Sites above 1 acre require NCDEQ stormwater plan review, which runs 30 to 60 days on top of the local permit. Most 8-stall Supercharger builds land below the 1-acre threshold when they slot into an existing parking lot.

What warranty do we carry on Supercharger pad work?

10-year material-and-labor warranty on the slab and rebar work, 5-year warranty on the anchor-bolt pull-out capacity, 2-year warranty on the ground-resistance test result. The warranty covers pad settlement, cabinet-corner cracking, anchor-bolt loosening, and ground-ring corrosion. Warranty excludes vandalism, vehicle-impact damage, and equipment failures upstream of the concrete work.

Key takeaways

• 8-inch slab with #4 rebar at 12 inches on center is the working stall-bay spec. The 4- to 6-inch parking-lot default fails the Tesla site-acceptance walk within 12 to 24 months.
• 10-inch PSA cabinet pad with #5 rebar at 10 inches on center is separately poured and reinforced. The 12,000-pound anchor-bolt pull-out capacity is non-negotiable.
• Two 2-inch DC feeder conduits plus one 1-inch communications conduit per stall, pre-set to the Tesla design-package geometry with pre-pour verification photograph.
• Bonded ground ring, two 8-foot supplemental rods per PSA cabinet, rebar mat cad-welded to the ring at four points. Ground-resistance test below 25 ohms at commissioning.
• 4,500 PSI air-entrained mix at 5 to 7 percent air, water-to-cement below 0.45, shrinkage-reducing admixture in the mix. The mountain-approach corridor runs the top of the air-entrainment range.
• 7-day equipment install window, 28-day cure to public-charging live. Skipping cure protection to speed the schedule is a failed pull-out test at day 30.
• Pay nothing until the work is complete. We close out the subgrade proof-roll, the stub-out verification photograph, the anchor-bolt pull-out test, and the ground-resistance test before invoicing.

Ready to spec a Tesla V3 or V4 Supercharger, Electrify America, EVgo, or ChargePoint DC fast-charger concrete pad on an NC site? Call Local Concrete Contractor at (704) 318-2440 or request a no-deposit EV charging pad scope review and we will line-item the slab thickness, rebar spec, conduit pre-set geometry, anchor-bolt pattern, grounding plan, and cure schedule against the vendor design package before mobilization.