Screw Piles in Airdrie, AB

Below the surface in Airdrie

North of Calgary, along Nose Creek, Airdrie is built on a broad and nearly level clay plain. What causes trouble in that soil is not weakness so much as plasticity: the clay gains volume when it gets wet and loses it again as it dries. Those swings happen mostly within the top metre or two, and that is exactly where a deck ledger pulls away from a house or a garage door frame goes out of square. Think of it as a water-content issue first and a bearing issue second.

You might expect level ground to be kinder. It is the reverse. With almost no natural slope carrying runoff off the lot, how wet the clay gets is decided mostly by people — where the downspouts discharge, how the yard was graded, how much the lawn is watered, where the snow piles up. Every one of those tends to change once a homeowner moves in, and seldom in the foundation’s favour.

Then there is the pace of development. Entire subdivisions in Airdrie are cut and filled in one pass long before construction starts, so the back yard of a brand-new home may rest on imported fill whose depth no one on site can tell you — and it often changes from one side of the lot to the other. That is the reason a screw pile foundation here is accepted on the installation torque we actually measure, not on a depth borrowed from the neighbour’s install.

The projects we see locally

Airdrie’s homes are mostly young, so we are seldom rescuing an old failing foundation. What we see instead is owners adding to a newer house: rear decks and covered decks, pads for hot tubs, detached or oversized garages, sunrooms, and now and then a retrofitted side entrance. The lots tend to be open and flat with room for equipment — nothing like squeezing into a Calgary infill yard — so getting a machine in is rarely what slows the job down.

Cross the city limit and the work turns rural. Acreage owners want post-frame shops, sheds for equipment and animal shelters, all sitting on that same clay and with no municipal services. These are tall, lightweight buildings that catch the wind, which means resisting uplift is every bit as important as carrying weight. Helical screw piles are installed with a recorded value for both.