Ground Screws vs Sonotube for Deck Footings in Ontario

You're planning a deck and your builder just mentioned ground screws as an alternative to traditional concrete footings. Or maybe you're DIYing it and wondering if those spiral metal posts you saw online actually work in Ontario's freeze-thaw climate.

Here's what you need to know: both ground screws and sonotubes can meet Ontario Building Code requirements, but they work completely differently and suit different situations.

What Are Ground Screws?

Ground screws are galvanized steel shafts with helical blades that twist into the soil. They look like giant screws, typically 30-48 inches long, with mounting brackets on top for deck posts.

You install them with a hydraulic or electric driver—think impact wrench meets auger. No digging, no concrete, no curing time.

Key specs:

• Diameter: 3-4 inches typical
• Length: 30-48 inches (must reach below frost line)
• Load capacity: 5,000-15,000 lbs depending on model and soil
• Material: Hot-dip galvanized steel
• Installation time: 5-10 minutes per screw

Ground screws entered the North American market from Europe, where they've been used for solar panel arrays and temporary structures for decades. They're now gaining traction in residential decking.

What Are Sonotubes?

Sonotubes are cardboard concrete forms—cylindrical tubes you set in a hole, fill with concrete, and embed a post base or J-bolt while the concrete is wet.

This is the traditional method, what 95% of Ontario decks currently use.

Typical setup:

• Tube diameter: 8-12 inches
• Footing depth: 48 inches minimum (Ontario frost line is 48 inches or 1.2 m)
• Concrete volume: 1.5-2.5 cubic feet per footing
• Installation time: 30-60 minutes per footing (plus 7 days cure time)
• Cost: $25-40 per footing in materials

The concrete cures around the embedded hardware, creating a massive anchor below the frost line that resists heaving from freeze-thaw cycles.

Installation Comparison

Ground Screws

You'll need:

• Hydraulic or electric driver ($2,000-5,000 to buy, $150-300/day to rent)
• Two people (one to operate driver, one to monitor level)
• Layout strings and marking spray

Process:

1. Mark footing locations

2. Start screw vertically using driver

3. Monitor with torpedo level as it descends

4. Stop when bracket reaches grade or specified height

5. Attach post base hardware

6. Move to next location

Total time for 8 footings: 1-2 hours.

No excavation unless you hit rock or hardpan. No concrete mixing. No waiting.

Sonotubes

You'll need:

• Post hole digger or auger (manual or gas-powered)
• Sonotube forms
• Concrete (bagged or truck delivery)
• Post bases or J-bolts
• Gravel for drainage
• Level and bracing

Process:

1. Mark footing locations

2. Dig holes 48+ inches deep, 12-16 inches diameter

3. Add 6 inches gravel base

4. Set sonotube, level and brace

5. Mix and pour concrete

6. Embed post base hardware while wet

7. Level and align all bases

8. Wait 7 days minimum before loading

Total time for 8 footings: 6-10 hours of labor, plus 7-day cure.

If you're DIYing, sonotubes mean renting an auger ($80-120/day), making multiple concrete runs, and a full weekend of work. Ground screws compress that into an afternoon—if you can rent the driver and if your soil cooperates.

Cost Breakdown (2026 KWC)

Ground Screws:

• Materials: $50-80 per screw
• Specialized driver rental: $150-300/day
• Installation labor (contractor): $30-50 per screw
• Total per footing (DIY): $50-80 + driver rental
• Total per footing (contractor): $80-130

Sonotubes:

• Sonotube form: $8-15
• Concrete (2 cu ft): $12-18
• Post base hardware: $5-12
• Gravel: $3-5
• Auger rental (DIY): $80-120/day (split across all footings)
• Installation labor (contractor): $40-70 per footing
• Total per footing (DIY): $28-50 + auger rental
• Total per footing (contractor): $68-120

For a typical 12×16 deck with 8 footings:

• Ground screws (DIY): $400-640 + $150-300 driver rental = $550-940
• Ground screws (contractor): $640-1,040
• Sonotubes (DIY): $224-400 + $80-120 auger = $304-520
• Sonotubes (contractor): $544-960

Ground screws are competitive with concrete when a contractor is installing—labor savings offset material cost. DIY, sonotubes are cheaper unless you already own a hydraulic driver.

Soil and Site Conditions

Ground screws aren't universal. They need torque-in capacity—the driver must be able to twist them to depth without hitting obstacles.

Where Ground Screws Work Well

Sandy or loamy soil: Ideal. The blades cut through easily and the soil compacts around the helixes, creating solid bearing.

Clay: Works if the clay isn't rock-hard dry or saturated. Moisture content matters. Ontario's clay can be challenging in mid-summer drought or spring thaw.

Light gravel: Manageable with powerful drivers.

Where Ground Screws Struggle

Rocky soil or bedrock: If you hit solid rock at 30 inches, you're done. Can't drill through it. Concrete footings can be poured shallower and wider with engineer approval in rock.

Heavy boulder content: Large stones stop the screw mid-installation. You won't know until you try.

Very soft or organic soil: The screw goes in easily but may not develop rated load capacity. Needs professional assessment.

High water table: Ground screws work, but saturated soil reduces lateral stability. Sonotubes can be poured below water (use a tremie method).

In KWC, soil varies dramatically. Downtown Kitchener near the Grand River? Often sandy with pockets of clay. Waterloo near Laurel Creek? Clay-heavy. Cambridge on the moraine? More gravel and cobbles. If you're not sure what's 4 feet down, sonotubes are safer.

Frost Heave Resistance

Ontario's frost line is 48 inches. Anything shallower risks heaving—soil freezing, expanding, and pushing the footing upward in winter, then settling in spring. This creates joist bounce, railing wobble, and ledger separation.

Sonotubes

When installed correctly (base below 48 inches, proper diameter), concrete footings have massive surface area and weight. They resist vertical movement through:

• Sheer mass (150-300 lbs of concrete per footing)
• Friction against surrounding soil
• Bell-bottom shapes that lock below the frost line

Track record: Decades of proven performance in Ontario. When a deck heaves, it's usually because the footing was too shallow, not because concrete failed.

Ground Screws

Ground screws resist frost heave through:

• Helical blades below the frost line that mechanically lock into soil
• Minimal surface area in the frost zone (the shaft is narrow)
• The helix design creates upward resistance

Track record: Proven in European freeze-thaw climates similar to Ontario's. Newer in Canada but engineering data supports their use.

The concern isn't whether the screw itself moves—it's whether the surrounding soil grips the helix adequately. In loose or sandy backfill, a screw can shift more than a massive concrete column.

If your deck attaches to the house via a ledger, any differential movement between footings causes serious problems. Concrete's uniformity is an advantage here.

Building Code and Permit Acceptance

Ontario Building Code (OBC) does not explicitly list ground screws in the prescriptive deck foundation tables. This doesn't mean they're prohibited—it means they require engineered approval.

Getting Ground Screws Approved

You'll need:

1. Professional engineer's stamp: A P.Eng must certify that the ground screws meet OBC structural load requirements (typically 40 psf live load, 10 psf dead load for decks).

2. Manufacturer specifications: Load capacity charts, installation torque values, and frost heave resistance data.

3. Soil assessment: The engineer may require a site visit or soil test to confirm bearing capacity.

Cost: $500-1,200 for the engineer's report and stamp.

In Kitchener, Waterloo, and Cambridge, building departments will accept engineered ground screw designs. The permit reviewer will check:

• Frost depth compliance (48" minimum)
• Load capacity for your deck size and configuration
• Professional seal on the drawings

Processing time is the same as any deck permit—see our timeline guide here.

Sonotubes

Sonotubes follow OBC's prescriptive path. No engineer required if you follow the code tables:

• Minimum 48" depth
• Concrete footing diameter based on soil bearing capacity (typically 8-12" tube)
• Proper post-to-footing connection

Your permit drawings just need to show footing depth, diameter, and spacing. See what's required in our permit drawings checklist.

Long-Term Durability

Ground Screws

Corrosion is the primary concern. Hot-dip galvanized steel resists rust, but Ontario soil chemistry varies. Acidic soil (low pH) or high chloride content (near roads that get winter salt runoff) accelerates corrosion.

Manufacturers typically warranty ground screws for 25-50 years in residential applications. Real-world lifespan depends on:

• Coating quality (G185 or G235 galvanization rating)
• Soil pH and moisture
• Drainage around the screw

If your yard has standing water or poor drainage, concrete is more durable.

Sonotubes

Concrete deteriorates slowly from freeze-thaw cycles, sulfate attack (in some soils), and rebar corrosion (if rebar is used and moisture penetrates). But we're talking 50-100+ year lifespan in typical Ontario conditions.

The sonotube cardboard disintegrates after the pour—it's just a form. What remains is a solid concrete column, and concrete improves with age as it continues curing.

Deck posts rot before footings fail. Even pressure-treated posts in ground contact last only 15-25 years. Your footings will outlive multiple deck rebuilds.

Installation Flexibility

Adjustability

Ground screws: If you install one slightly out of alignment (1-2 inches off layout), you can unbolt it, twist it out, and reinstall nearby. Not easy, but possible.

Sonotubes: Once concrete cures, you're locked in. If a footing is misplaced, you're either building around it or breaking it out and re-pouring.

Height Adjustments

Ground screws: Stop twisting when the bracket reaches your target height. Easy to get all footings level on sloped terrain—just vary how deep each screw goes.

Sonotubes: On slopes, you either dig to different depths (keeping the base at 48" but varying tube height) or pour different amounts of concrete. Then you cut posts to final height. More room for error.

Retrofit and Additions

Ground screws: Can be installed in tight spaces where excavation is difficult—next to existing decks, near utilities, or in landscaped areas. Minimal soil disturbance.

Sonotubes: Digging creates mess. You'll damage grass, gardens, and irrigation. Need equipment access.

If you're adding onto an existing deck or working in a finished backyard, ground screws are cleaner.

Environmental and Site Impact

Ground screws:

• No concrete waste
• No excavated soil to haul away (most screws displace <0.1 cu ft)
• Reversible—unscrew them and the site is nearly undisturbed
• Carbon footprint: Steel production is energy-intensive, but the smaller mass vs. concrete reduces overall emissions

Sonotubes:

• Concrete production is carbon-heavy (cement is ~8% of global CO2 emissions)
• Excavated soil disposal (or spreading around the yard)
• Cardboard tubes are biodegradable but coated with wax
• Not reversible—breaking out cured footings requires jackhammers

If sustainability matters to you, ground screws edge ahead. But we're talking about 8-12 small footings, not a foundation—the deck material choice (composite vs. wood) has 10x more environmental impact than the footings.

Contractor Availability

Most deck builders in KWC install sonotubes. That's what they know, what their crews are trained on, and what their insurance covers.

Ground screw installation requires specialized equipment and training. Only a handful of builders currently offer it. If you want ground screws:

1. Ask specifically when requesting quotes—see our deck quote checklist here

2. Expect fewer bids

3. Verify they have the hydraulic driver (not trying to DIY it with an impact wrench—won't work)

DIY? If you're handy and can rent a driver, ground screws are easier than concrete once you have the tool. But the driver is expensive and not widely stocked at rental yards. Call ahead.

When to Choose Ground Screws

Ground screws make sense when:

• You're building on sandy, loamy, or well-draining soil with no rock
• You need fast installation (contractor has back-to-back projects, or you want to build in a tight timeline)
• Your site has limited access for concrete trucks or equipment
• You're building a temporary or semi-permanent structure that might be relocated
• You value low site disturbance—landscaping stays intact

They're especially popular for low decks on flat lots where a traditional excavator would tear up finished grading.

When to Choose Sonotubes

Stick with concrete footings when:

• Your soil is unknown, rocky, or clay-heavy
• You want maximum long-term durability and proven track record
• You're DIYing on a budget and have time for concrete to cure
• Your builder specializes in traditional methods (no need to complicate the project)
• You're building a large or heavy deck (hot tub, heavy roofing, second story)
• You don't want to pay for engineering approval

For most homeowners in Kitchener, Waterloo, and Cambridge, sonotubes remain the default. They're predictable, affordable, and every inspector knows exactly what to look for.

Helical Piles: The Third Option

If you're comparing foundation systems, also consider helical piles—steel shafts with helical blades, driven deeper than ground screws (6-15+ feet) to reach load-bearing strata.

Helical piles cost $150-300 each installed but offer superior load capacity and are used for engineered applications like hot tub decks or challenging soil. Read our full comparison of helical piles vs. concrete footings here.

Ground screws are essentially shallow helical piles—they share the same concept but target residential decks at code-minimum depth.

Common Questions

Can I install ground screws myself?

Yes, if you can rent a hydraulic driver. Rental availability is limited in KWC—call equipment rental yards well in advance. You'll also need a helper to monitor plumb as the screw descends. Hand-twisting or using an impact wrench won't work—you need hundreds of ft-lbs of torque.

Do ground screws meet Ontario Building Code for decks?

They can, but you need a professional engineer's stamped design. The OBC doesn't include ground screws in its prescriptive footing tables, so they require engineered approval. Budget $500-1,200 for engineering. Sonotubes meet code prescriptively—no engineer needed if you follow the standard depth and diameter requirements.

How deep do ground screws need to go in Ontario?

Minimum 48 inches to get below the frost line, same as concrete footings. Some installers go 54-60 inches in heavy clay or if the engineer specifies deeper penetration for load capacity. The helical blades must sit entirely below the frost zone to resist heaving.

What happens if a ground screw hits rock?

Installation stops. You can try a different location a few feet away, but if bedrock is shallow across your site, ground screws won't work. Concrete footings can be engineered for shallower depth when poured directly on bedrock, so they're more forgiving in rocky terrain.

How long do ground screws last compared to concrete?

Manufacturers warranty galvanized steel ground screws for 25-50 years. Concrete footings last 50-100+ years in typical Ontario soil. Both will outlast your deck structure—pressure-treated posts and framing need replacement every 20-30 years regardless of footing type. Corrosion is the main long-term risk with ground screws, especially in acidic or chloride-rich soil.