Local pros · Concrete
Hiring a concrete contractor for pads, slabs and footings
Heavy outdoor products are only as good as what they sit on. A full hot tub can weigh 3,000 to 6,000 pounds, a standby generator and a heat pump condenser need a level base, and a louvered pergola has to be anchored against wind. A small concrete job done once, to the maker's specs, is cheaper than lifting and re-leveling later.
Hire right once: Give the contractor the product's installation manual before they quote, and have the pad sized to its footprint, weight and clearances, with room to spare for a walkway or service access.
Before you hire, check:
- The maker's pad, footing and clearance requirements, in writing from the manual
- Local frost depth and whether a permit or inspection is required
- Reinforcement, base preparation, drainage and cure time in the quote
What they do for these products
- Hot tubs: a flat, reinforced slab or an alternative base sized to the tub's filled weight.
- Standby generators and heat pump condensers: a level pad (concrete, or the composite or gravel base the maker allows) at the right distance from the house.
- Pergolas: footings or piers, or a slab that can take the kit's anchors.
- Saunas, patios and grills, gym equipment: a level, drained base; a patio slab for furniture and a grill; a sound garage slab for racks.
Hot tub pads
- Weight: HomeGuide lists about 3,000 lb filled for a 2–3 person tub, 4,000 lb for 4–5 people and 6,000 lb for 6–7 people.[1] A 7 × 7 ft tub at 4,000 lb puts roughly 80 pounds per square foot on its footprint, about twice a typical deck's design load; see where it sits.
- Slab: the usual choice is a reinforced concrete slab, commonly 4 to 6 inches thick, extending a little past the tub's footprint and graded so water drains away.[2] Get the exact thickness and reinforcement from the tub maker and your contractor.
- Alternatives: compacted crushed gravel with pavers, a prefabricated plastic or composite spa pad, or a reinforced deck designed for the load. HomeGuide prices gravel at $1–$3 per square foot, plastic pads $4–$7, concrete $5–$10, pavers $10–$17 and reinforced decks $15–$30.[1]
- Not grass or bare soil: the tub can sink or go out of level.[1]
- Do the trenching first: have the electrician lay conduit before the pad is poured. See the electrician guide.
Standby generator and heat pump condenser pads
- Follow the installation manual. Makers specify the base (many standby units sit on a gravel bed, a composite pad or a concrete slab), the pad size, and the clearances from the house, windows, doors and vents. Local code and fuel-gas rules can add requirements.
- Level matters: a tilted pad strains the unit and can affect drainage and vibration. Heat pump condensers should sit above the expected snow line and away from roof drip lines, with meltwater draining away from paths where it could refreeze.
- Cost: the generator cost guide cites a concrete pad at about $150–$400 as a line item.
- Many installers pour or place the pad as part of the job. Ask whether it's included.
Pergola footings and piers
- Anchors: light kits may bolt to an existing slab with expansion or wedge anchors; heavier aluminum and louvered kits often call for the maker's post bases anchored into a slab of a minimum thickness, or into individual footings or piers.
- Footings and piers: poured concrete piers (often formed with a tube) at each post, sized and spaced to the kit's manual and local loads. Check the kit's wind and snow ratings against your site; see the pergola guide.
- Frost depth: where the ground freezes, footings should extend below the frost line to avoid heave that racks the frame.[3]
- Existing patio: don't assume it will hold anchors. A thin or cracked slab may need cutting out for footings.
Saunas, patios and garage slabs
- Saunas: an outdoor barrel or cabin needs a level, drained base: a slab, pavers on compacted gravel, or a gravel bed with a frame, per the maker's manual. See the sauna guide.
- Patio slabs for furniture and grills: a 4-inch broom-finish slab is typical, sloped slightly away from the house. Keep grills clear of the house and overhangs per the grill maker.
- Garage slabs for gym equipment: garage floors are commonly 4 to 6 inches thick.[2] Racks and plate-loaded machines concentrate load at their feet; inspect the slab for cracks, settling and thickness, and ask a contractor before bolting a rack down. See the home gym guide.
Frost line by region
Frost depth is set locally, so get the number for your address from the building department. It ranges from essentially none along the Gulf Coast and in the far South to several feet across the northern tier, and mountain areas can be deeper. The International Residential Code requires exterior footings to extend below the frost line.[3] In the South and Southwest, pads and shallow piers are common; in the North, expect deeper footings, or a pad designed to float with the ground, so ask your contractor which approach local inspectors accept.
Reinforcement, permits and cure time
- Reinforcement: contractors use rebar, welded wire mesh or fiber in the mix; larger or heavily loaded slabs get reinforcement and thicker edges.[2] Ask which and why.
- Base prep: a compacted gravel base helps prevent shifting and cracking; HomeGuide prices gravel at $1–$3 per square foot.[2]
- Permits: small patios and pads often don't need a permit, but structures and footings for roofed pergolas, and some generator installations, do. Ask your building department, and check HOA rules and setbacks.
- Cure time: HomeGuide says concrete can be walked on in 1–2 days, driven on after 1–2 weeks, and is fully cured after about 28 days.[2] Ask your contractor and the product maker when it's safe to set a filled hot tub or a heavy rack on the slab, and don't rush it.
Slab volume calculator
Concrete slab volume calculator (cubic yards and bags)
Length × width × thickness, plus 10% for waste, in cubic yards and bags.
How it works: Cubic feet = length × width × thickness ÷ 12; cubic yards = cubic feet ÷ 27; add 10% for waste and uneven subgrade. Bags assume common labeled yields: 80 lb ≈ 0.60 cu ft, 60 lb ≈ 0.45 cu ft. Order ready-mix by the cubic yard for anything over about 1 cubic yard.
Estimate only; confirm with your installer or the manufacturer.
Sources for this tool
Questions to ask
- Have you read the product's installation manual? What pad size, thickness and clearances does it call for?
- How thick will the slab be, and how is it reinforced?
- What's the local frost depth, and how deep will footings or piers go?
- What's the base preparation and how will water drain away?
- Who pulls any permit, and is HOA approval needed?
- How long before I can set the hot tub, generator or rack on it?
- Is the price itemized (excavation, base, forms, reinforcement, pour, finish, cleanup)?
- What warranty do you give on cracking and settling?
Typical costs
| Job | Typical range |
|---|---|
| Concrete slab, installed | $6–$12 per sq ft; materials $3–$7, labor $3–$5[2] |
| By thickness | 4 in $6–$8; 6 in $8–$10 per sq ft[2] |
| Hot tub concrete pad | $500–$2,500 ($5–$10 per sq ft)[1] |
| Generator concrete pad (line item) | $150–$400[4] |
| Patio slab | $4–$12 per sq ft; $1,000–$6,000 for 200–400 sq ft[2] |
| Garage floor, 400–576 sq ft | $2,400–$6,900[2] |
| Gravel base | $1–$3 per sq ft[2] |
| Concrete removal | $3–$8 per sq ft[2] |
Small pads often cost more per square foot than large slabs because of minimum charges. Stamped or decorative finishes cost more.
Related buying guides
- Hot tub buying guide and standby generator costs
- Heat pump buying guide and pergola buying guide
- Pergola and deck builders and licensed electricians
Sources
- HomeGuide, Hot Tub Installation Cost (2026): homeguide.com
- HomeGuide, Concrete Slab Cost (2026): homeguide.com
- 2024 International Residential Code, Chapter 4 Foundations (UpCodes): up.codes
- HomeGuide, Generator Cost (2026), as cited in our generator cost guide: homeguide.com