Screw Piles in Strathmore, AB

Below the surface in Strathmore

Drive east from Calgary and the country gets flatter and drier. Strathmore has neither a river valley running through it nor any foothills relief — it is level prairie over clay-rich glacial till, and what moves foundations here is the change of seasons rather than a river. Being at the dry end of our service radius, the clay acts the part: it soaks up moisture and swells, then contracts sharply over a dry summer. That yearly cycle is what pulls shop doors out of line and heaves a corner of a slab.

Irrigation makes things less predictable than “open prairie” implies. The Western Irrigation District is headquartered in Strathmore, and a network of canals and laterals going back to the Canadian Pacific irrigation project crosses the farmland all around town. A yard site beside a canal, a lateral or a watered quarter section can have its own moisture pattern that has little to do with rain — wet all through the irrigation season and dry once it ends. Better to bring that up when we quote than to find it out later.

Out here, resisting uplift counts just as much as carrying weight. Most buildings going up around Strathmore are light with big roofs, so wind pulls them upward and swelling clay pushes them upward as well. A helical screw pile handles load in either direction through one connection; a pad footing only handles one.

The projects we see locally

Construction around Strathmore and the rest of Wheatland County does not look like a Calgary subdivision. The jobs that keep coming up are acreage post-frame shops, implement and machinery storage, livestock shelters, grain bin pads and expanding yard sites. A lot of these buildings are unheated and used only part of the year, so the soil right under them freezes every winter — precisely when a shallow pad or thickened-edge slab is most at risk of heaving.

Within town the work is familiar residential fare: decks, detached garages and additions in the newer neighbourhoods, along with light commercial buildings on the Trans-Canada corridor. Grain bin pads deserve their own mention. Loaded, a bin puts a heavy load on a small footprint; empty, it becomes a light structure presenting a huge surface to the wind, and its screw pile foundation has to work in both conditions.