What Are Helical Piles?
How Screw Pile Foundations Work

How a helical pile actually goes in

The install looks simple from the driveway. A machine with a hydraulic drive head grabs the pile, lines it up on the mark, and turns. The helix plates pull the shaft down the way a wood screw pulls into a stud. Extensions get bolted on as the pile goes deeper.

What matters is what the machine reports back. The drive head measures how hard it has to work to keep turning, and that installation torque tracks the strength of the soil the helix is cutting through. When the torque climbs to the number the project engineer specified, the pile is in competent ground and the crew stops. Depth is an outcome, not a target. Two piles ten feet apart on the same lot can finish at different depths and both be right.

Once the pile is at capacity, a bracket or cap goes on top and the structure bolts to it. A framing crew can start the same day.

The parts of a screw pile

How much weight can one hold?

There is no single answer, and anyone who gives you one without seeing the site is guessing. Capacity comes from three things: the size of the shaft, the size and number of helix plates, and the soil the plates end up in. A small deck pile and a pile under a commercial column are the same idea at very different scales.

The useful part is that capacity gets confirmed on every single pile. Installation torque is correlated to capacity using the method set out in ICC-ES AC358, the acceptance criteria for helical pile systems, and the readings get recorded. Your engineer sets the required number before the crew arrives, and the field report shows whether each pile hit it. Compare that with a poured footing, where nobody measures anything after the truck leaves.

Full material and installation specs are on our helical piles page.

Helical pile sizes and what each one is for

We install four shaft sizes: 2 3/8 inch, 3 inch and 3 1/2 inch round shaft for residential and light commercial work, and a 6 5/8 inch large-diameter shaft for heavy commercial loads. Helix plates come in 8, 10 and 12 inch diameters, and a pile can carry more than one plate when the soil or the load calls for it.

Capacity is not printed on the shaft. It comes from the shaft, the helix configuration and the soil the plates finish in, and it is proven on site by the installation torque (more on that below). The figures below are the configurations on our helical piles specification page; the rated capacities for a specific configuration are in the product evaluation report, which we supply with the engineering package on request.

Three things move a job up the table: heavier loads, weaker soil, and lateral or uplift demand (wind on a sign, ice on a dock, a tall deck). Your engineer picks the configuration; the torque log proves it in the ground.

Torque to capacity, explained plainly

A helical pile’s capacity is read off the installation torque with one short equation: ultimate capacity = Kt x final installation torque. Torque is how hard the drive head has to work to keep the pile turning, in foot-pounds; Kt is a capacity-to-torque factor that belongs to the specific pile product, established by load testing and published in its evaluation report.

The reason this works is that both numbers come from the same thing: the strength of the soil gripping the helix plates. Firmer ground means more bearing resistance, so the drive head pushes harder and the torque climbs. That same bearing resistance is what carries the structure once the pile is in. Torque is a live measurement of the soil at bearing depth, which is exactly what an engineer needs and exactly what a poured footing never gives you.

Kt is a property of the pile, not the soil. Slim round shafts around 2 7/8 inches commonly run near a Kt of 9 per foot; larger pipe shafts of 3 1/2 inches and up drop to around 6 or 7 because more of the torque is shaft friction; square bar shafts often sit near 10. A worked example: a gauge that stops climbing at 8,000 foot-pounds on a pile with a Kt of 9 gives an ultimate capacity of roughly 72,000 pounds. Engineers then apply a factor of safety, commonly 2 for helical piles under ICC-ES AC358, so that pile is carrying an allowable load in the range of 36,000 pounds. The only Kt that is valid for your job is the one in that pile’s evaluation report, applied by your engineer.

The install log is the proof. Every pile gets its final torque and depth recorded, and the field report goes to the project engineer or the building inspector. That is why a helical pile is the only common foundation where capacity is confirmed on every single element. The full walkthrough, with a sample torque chart, is in understanding helical pile torque to capacity ratios.

Where helical piles make the most sense

They are not the answer to everything, but in Ontario they solve a lot of expensive problems:

• Frost-prone ground. The pile bears below the frost line, so seasonal heave has nothing to lift.
• Soft, wet or filled soil. The helix keeps going until it finds ground that can carry the load, instead of sitting on whatever happens to be at footing depth.
• Tight access. Compact equipment gets into back yards and between houses without wrecking the lawn or a neighbour’s driveway.
• Winter builds. Nothing has to cure, so cold weather does not stop the schedule.
• Existing buildings. Piles can be installed beside a settling foundation and brackets transfer the load onto them, which is how helical underpinning works.
• Water and shoreline. Docks, boathouses and boardwalks sit on piles because there is no practical way to pour a footing there.

A full concrete basement still makes sense on plenty of builds. If you want the side-by-side, read helical piles vs concrete footings.

How Ontario soils behave under a helical pile

Soil decides depth and helix choice more than anything else. The pile keeps turning until the torque says the plates have found competent ground, so the same structure can need a 10-foot pile on one lot and a 30-foot pile on the next.

• Clay. Most of the GTA, York Region and Durham sits on glacial clay and clay till. Wet clay near the surface is weak and moves with the seasons; the competent layer of stiff clay or till is usually 4 to 9 metres down. Clay lots need longer piles and, in soft clay, a larger helix to develop bearing. See how deep helical piles need to go in Ontario clay.
• Sand and gravel. Common across Simcoe County and along Georgian Bay. Torque builds quickly and piles tend to finish shallower, often within a few metres of clearing the frost line. Loose sand at the surface is handled by driving through it, not by sitting on it.
• Fill. New subdivisions and any lot that has been regraded carry a disturbed layer of unknown strength. A footing poured on fill is a gamble; a pile is driven straight through it to undisturbed ground below, and the torque reading shows the transition.
• Organics and marsh. Around the Holland Marsh and other low ground, deep organic muck sits over mineral soil. Piles pass through the muck with almost no torque and then climb sharply when they reach the mineral layer, which is where they bear.
• Rock. On the Canadian Shield in Muskoka a thin layer of soil covers granite. Piles are torqued down to refusal on the rock and bear on it, which suits steep and waterfront lots where a footing cannot be poured.

Water changes all of it. A high water table or a wet season lowers soil strength, so the same lot can produce a deeper pile in April than in August. That is one more reason capacity is measured on the day rather than assumed from a drawing.

What moves the price of a helical pile job in Ontario

We quote per project rather than per pile, because the pile count is only part of it. The same deck can cost noticeably different amounts on two lots a street apart, and the reasons are almost always in this list.

• Number of piles. Set by the loads and the beam spans on the drawing, not by square footage. A hot tub or a roof adds piles; a well-designed beam layout removes them.
• Depth to bearing. The single biggest variable. Sandy ground that gives torque at 10 feet costs less in steel, extensions and rig time than clay that does not firm up until 25 or 30 feet. This is a soil question, and a soil report or a nearby job usually tells us before we quote.
• Shaft and helix size. A commercial column or an underpinning bracket needs more steel than a deck post, and large-diameter piles need a bigger rig.
• Access. A machine that can drive into the yard costs less to run than one that has to be craned over a house, tracked down a slope or hand-carried to a shoreline. Gate width, slope and overhead wires all show up in the price.
• Engineering and permits. Stamped drawings, a soil report and inspection visits are extra line items on permitted work and are not needed on a small unpermitted deck.
• Season. Frozen ground does not stop us, but deep frost adds time per pile, and spring water tables can add depth. Booking in the shoulder seasons is usually the easiest scheduling.
• Removal and reuse. Temporary structures can be quoted with pile removal, which recovers some of the steel value.

We do not publish price ranges on this page because the honest range for a deck and the range for an underpinning job do not overlap, and a number without the loads behind it misleads more than it helps. Send us the loads, the address and a site photo and we can usually tell you the same day where a project lands. Ask for a quote.

The installation sequence, start to finish

A residential helical pile job is usually one site visit for the install itself, with the engineering and layout done beforehand. Here is the order it happens in and roughly how long each step takes.

1. Site review. You send drawings or a description, a site photo and the address. We confirm access, the number of piles the loads call for and the likely shaft size, and quote the project. Most of this happens on the phone and by email within a few days.
2. Engineering, where required. If the structure needs a permit or an engineer is already involved, the pile layout and capacities are set on a stamped drawing before anyone mobilises. A soil report, when one exists, sets the predicted depth.
3. Layout. Pile locations are marked on site from the drawing. Locates are cleared before any pile goes in.
4. Installation. The rig drives each pile, adding extensions as it goes, until the torque reaches the specified value. A deck or shed is a few hours; most residential jobs are done in a day; commercial work is scheduled around the drawing review rather than the install itself.
5. Caps and brackets. The connection hardware goes on at the finished height. For underpinning, brackets are fastened to the existing footing and the load is transferred onto the piles.
6. Torque log handoff. The field report, with final torque and depth for every pile, goes to you, your engineer or the inspector. Framing can start the same day, because there is nothing to cure.

When you need an engineer and a permit in Ontario

The foundation follows the structure. If the deck, addition, garage or building needs a building permit under the Ontario Building Code, the pile foundation is part of that permit, and the municipality will normally want stamped drawings for the pile layout and the installation torque records at inspection. Small, low structures that do not need a permit do not need engineered piles either, although the piles still get installed to torque.

What the engineer needs from you is short: the drawings or a sketch of the structure with its dimensions; the loads, or enough about the structure for the engineer to work them out (a hot tub or a second storey changes everything); a site plan or survey showing where it sits; any soil report or nearby borehole data; and a note on access, since a lot that only fits a compact rig limits the shaft size. Our in-house engineering handles the layout and the stamped drawing on most projects, and we supply the mill certificate and product evaluation report when a reviewer asks for them.

Helical piles compared with the alternatives

Helical piles are not the answer to everything, and it is worth knowing when the other option is the better one. The short version: piles win on frost, soft ground, access, speed and winter; concrete wins when the design wants a full basement or a continuous slab.

The full cost, time and frost comparison with concrete is on helical piles vs concrete footings.

Glossary: the words people use for the same thing

Search for this product and you will find five or six names for it. They all describe a steel shaft with helix plates that is turned into the ground; the differences are mostly who is talking.

• Helical pile. The engineering and building-code term. Used on drawings, in evaluation reports and in ICC-ES AC358.
• Screw pile. The everyday term builders and homeowners use in Ontario. Same product.
• Helical pier. Common in foundation-repair language, usually for a pile with a bracket that supports an existing footing.
• Helix piling, helical piling. Alternative spellings of the same thing, more common in the UK and in older trade writing.
• Screw anchor, helical anchor. The same hardware installed to resist pull-out rather than to carry weight: guy anchors, tie-backs, uplift on solar racking.
• Helix plate. The steel disc welded near the tip that cuts into the soil and carries the load.
• Extension. A bolted-on shaft section that lets the pile reach whatever depth the torque demands.
• Kt. The capacity-to-torque factor for a specific pile product, from its evaluation report.
• Torque log, field report. The record of final torque and depth for every pile, which is the proof of capacity.
• Underpinning. Transferring an existing foundation’s load onto new piles through brackets, without rebuilding the foundation.