Concrete Pad for a Hot Tub in Spokane: Thickness, Weight, Wiring Clearances and Permits (2026)

Putting in a hot tub around Spokane? The concrete pad under it matters more than most people expect. A filled spa with people in it can weigh several tons, the major manufacturers spell out the pad they want, and the wiring rules decide where the pad can go before anyone sets a form. Here's what the manufacturers, the electrical code and the local permit offices say.

How heavy a hot tub really is

• Published load ratings: Hot Spring says its Vista and Grandee need a reinforced concrete pad or a deck that can carry more than 115 pounds per square foot
• Big spas and swim spas: Bullfrog Spas says the filled weight of a portable spa can run from 6,000 to 20,000 pounds, not counting occupants
• Use your model's number: the spec sheet or owner's manual lists the filled weight and the load the base needs to carry. Send it to us with your quote request

What the manufacturers ask for

The big brands agree on the basics:

• Hot Spring: a reinforced concrete pad at least 4 inches thick is required for the Vista and Grandee and recommended for its other Highlife models. The rod or mesh should be attached to a bond wire
• Bullfrog Spas: a pad at least 4 inches thick, reinforced with rebar or mesh attached to a bond wire, and 6 inches or more for larger or heavier spas, including swim spas
• Master Spas: a concrete pad at least 4 inches thick, reinforced with steel rebar in a grid, on a uniformly firm, continuous and level surface
• Level and flat: Hot Spring says its Vista and Grandee must not be shimmed, so the pad has to be poured flat, not fixed afterward
• Warranty: Hot Spring says structural damage from an inadequate foundation isn't covered under its limited warranty

Built for Spokane's winters

• Air-entrained concrete: a pad outside in Spokane goes through freeze-thaw every winter, so we pour an air-entrained mix. Our concrete PSI guide explains the code minimums for weather-exposed slabs
• Compacted base: a firm, well-drained gravel base keeps the pad from settling unevenly under a point load
• Reinforcement: rebar or mesh in the pad, as the manufacturers call for. Our rebar vs. mesh guide covers the options
• Frost depth: the City of Spokane and Spokane County set the official frost depth at 24 inches. A spa pad on grade doesn't need frost footings, but a gazebo, pergola or roof over the tub usually does. See our frost depth guide
• Drainage: we slope the surrounding patio away from the house so splash-out and snowmelt don't sit against the foundation

Plan the wiring before the pour

The electrical code sets distances that decide where the pad and the disconnect go. These come from Article 680 of the National Electrical Code, which the City of Spokane adopts in its 2023 edition:

• Maintenance disconnect (680.13): required for the spa equipment, readily accessible, within sight of the spa and at least 5 feet from the water, unless a permanent barrier is in between. "Within sight" means visible and no more than 50 feet away
• Emergency shutoff (680.41): required for spas at anything other than a one-family home, at least 5 feet away and within sight of the tub
• Receptacles: general receptacles have to be at least 6 feet from the inside wall of the spa, and receptacles rated 30 amps, 125 volts or less within 10 feet of the spa need GFCI protection
• Bonding: manufacturers want the pad's steel tied to a bond wire, and the code has equipotential bonding rules for the surfaces around a spa. Outdoor self-contained spas can be exempt from perimeter bonding if the rim sits at least 28 inches above any surface within 30 inches. Ask your electrician before we pour, because the bonding conductor has to be in place first
• Conduit: if the circuit runs under the patio, the conduit goes in before the concrete, not after

Permits around Spokane

• Electrical permit, City of Spokane: inside city limits, the City issues electrical permits and requires separate permits for electrical work tied to a pool or spa
• Electrical permit, unincorporated County: Spokane County says electrical permits for unincorporated areas come from Washington L&I, at 901 N. Monroe St. in Spokane
• Barrier or cover, City of Spokane: the City's swimming pool permit application says all pools, hot tubs and ponds more than 18 inches deep must be enclosed and inaccessible to small children, with self-closing, self-latching gates. It lists an ASTM F1346 safety cover spec sheet as one of the barrier details. Ask the City whether a pool permit applies to your spa
• Barrier or cover, Spokane County: residential spas and hot tubs holding water over 24 inches deep need a fence or barrier, but spas with a lockable safety cover that complies with ASTM F1346 are exempt
• Draining: the City's pool application says drainage to the sewer isn't authorized for residential pools, and water has to be dechlorinated and kept on site. Plan where a drained tub can soak in
• Other cities: Spokane Valley, Liberty Lake and other cities have their own rules, so we check your address before we quote

Sizing the pad

• Bigger than the tub: pour the pad larger than the spa's footprint, so the cover lift, steps and service panel all sit on concrete
• Service access: leave room to reach the equipment side of the tub
• Path from the door: a short concrete walk from the house is worth it in January
• Room for snow: leave space to shovel around the tub and the cover

A pad on its own, or part of a patio

Many hot tubs go on a section of a new patio. If you're adding a patio, our concrete patio cost guide and our stamped concrete vs. pavers comparison help you choose a finish. We can pour the spa area thicker as part of the same job.

What it costs

Hot tub pads are quoted per project, because thickness, reinforcement, access and site prep change with the spa and the yard. When the pad is part of a larger patio, Raven's current patio rates, including site prep and the pour, are about $12 to $20 per sq ft for broom finish and $18 to $30 per sq ft for stamped, depending on size and whether a pump is needed.

Get a hot tub pad quote

Raven Buildings pours concrete flatwork across Spokane and Eastern Washington, from spa pads to full patios and driveways. Call 509-350-2016 or request a free quote with your spa model, the spot you have in mind and your address.

Sources

• Patio pricing: Raven Buildings' current patio rates
• Hot Spring Spas, Pre-Delivery Instructions (PDF)
• Bullfrog Spas, Picking Your Hot Tub Foundation
• Master Spas, Hot Tub Backyard Planning Guide (PDF)
• Mike Holt, Swimming Pools and Spas, NEC Article 680 (PDF)
• EC&M, Spas, Hot Tubs, and Hydromassage Tubs
• City of Spokane, Residential Codes
• City of Spokane, Swimming Pool Permit Application (PDF)
• Spokane County, Building Permit FAQs
• City of Spokane / Spokane County Joint Policy BUILD-07, Official Frost Depth (PDF)