Delivery, foundations and site preparation
Screw pile foundations: what the code asks for under a small home
By Jonathan Kennedy, cabin owner and tiny home rental owner · Last reviewed October 28, 2026
A screw pile (or helical pile) foundation is a set of steel shafts with helical plates screwed into the ground, which carry a building on brackets instead of concrete footings. In Ontario, BC and Alberta, screw piles aren't one of the Building Code's standard Part 9 foundations, so under a home they're approved as an engineered design or alternative solution: expect an engineer's drawings, a torque record for every pile, and in many towns a CCMC evaluation report.
You're placing a tiny home, a garden suite or a cabin on a lot where pouring concrete is a pain: a slope, tree roots, a tight backyard, or a site the concrete truck can't reach. Screw piles go in with a machine, with no concrete to pour or cure. The question is what your building department needs to see.
Are screw piles allowed under the Building Code?
Yes, but not as a "recipe" foundation. Ontario's Part 9 foundation rules cover concrete, masonry, wood and ICF footings and walls on stable soil, and anything else has to be designed (2024 Building Code, Part 9). Screw piles get approved in one of two ways: as a Part 4 deep foundation designed by an engineer (Part 4), or as an alternative solution, with documents showing they perform at least as well as the standard approach (Division C, Part 2).
BC uses the same model: where a Part 9 building needs an engineered foundation, the engineer provides letters of assurance (Schedules B and C-B) for that part (BC Building Code 2024). In Alberta, Calgary asks for an APEGA engineer's stamped drawings for screw pile foundations under decks (Calgary).
Do screw piles need an engineer and a CCMC report?
An engineer, almost always; a CCMC report, in many towns. A CCMC evaluation report is the National Research Council's opinion that a specific pile product meets the National Building Code, under listed conditions. These are the requirements Ontario towns publish:
| Town | What it asks for |
|---|---|
| Huntsville | Registered engineer's approval, a product with a CCMC number on every pile, a manufacturer-certified installer, the engineer's minimum torque settings and a sealed certificate of conformity |
| Barrie | A stamped engineer's design with a soil analysis, and a CCMC report for the product |
| Township of Perry | An engineered design, a qualified installer, and torque reports before the framing inspection |
Sources: Huntsville, Barrie, Perry. Whitehorse's 2026 bulletin, drawn from the CCMC's technical bulletin, adds hot-dip galvanizing of at least 610 g/m² or engineer-specified corrosion protection (Whitehorse). CCMC reports have re-evaluation dates, so ask the installer for a current one.
Our take: hire an installer who hands you the engineer's letter and the torque log without being asked. The cheapest pile quote that leaves you to find an engineer later is the half-measure: the inspector won't pass the framing without those papers.
What is a torque log, and why does the inspector want it?
It's the record of how hard each pile turned at its final depth, which is how the installer proves the pile reached soil that can carry the load. Part 4 requires continuous field review of every deep foundation unit with the details recorded for each one (Part 4). A federal pile specification, for example, requires torque recorded continuously, especially over the last 1.5 m, with calibrated equipment (Parks Canada spec).
How deep do screw piles need to go for frost?
Below frost, unless the building is small enough to be exempt. Ontario's table sets 1.2 m, but not less than the depth of frost penetration, for clay or poorly defined soils under unheated space, with no minimum on rock (Part 9). BC's 2024 code has the same table (BCBC). Your building department sets the local frost depth.
Small buildings get a break: the depth table doesn't apply to a one-storey accessory building of 55 m² or less with its floor joists no more than 600 mm above the ground, or to a home built to pass the CSA Z240.2.1 deformation test. That covers many bunkies, cabins and factory-built units.
Can a tiny home or garden suite sit on screw piles?
Yes, with a permit. Ontario's tiny home guide says a tiny home needs a building permit and must be secured to the ground, on Building Code footings or foundations or anchored to CSA Z240.10.1, and the inspector checks it on site (Ontario tiny home guide). For a tiny house of 37 m² or less built in one place and moved to another, the permit at the receiving site covers the installation and the foundation (Division A).
What does a screw pile foundation cost?
A foundation for a garden suite, on screw piles or a slab, costs about $8,000 to $25,000 by our 2026 estimate, from an industry source we use as a range check. No government or trade association publishes screw pile prices; the count of piles, the soil and the access drive the quote. Add the engineer's design if the installer doesn't include it, and compare it with a concrete footing quote for the same building.
When aren't screw piles the right choice?
On shallow bedrock or ground full of large boulders, where the piles can't reach the depth or torque they need; a US transportation research summary flags both (Iowa DOT). Uncontrolled fill and sensitive clays need on-site load tests. On those sites, ask a geotechnical engineer before you pick a foundation.
Questions people ask
- Do I need a permit for screw piles under a tiny home?
- Yes. A tiny home needs a building permit in Ontario, and the foundation or anchoring is inspected on site. Screw piles under a home are approved as an engineered design or alternative solution.
- Are screw piles approved in Ontario?
- Yes, as an engineered (Part 4) foundation or an alternative solution, not as a standard Part 9 foundation. Many municipalities also ask for a CCMC evaluation report for the product.
- How deep do screw piles go in Ontario?
- Below the local frost depth, which your building department sets; the Building Code's minimum is 1.2 m for clay soils under unheated space. Small accessory buildings of 55 m² or less with low floors are exempt from the depth table.
- Are screw piles cheaper than concrete?
- It depends on the site, so compare quotes for the same building. Our 2026 estimate for a garden suite foundation, screw piles or slab, is $8,000 to $25,000.