In the fall of 2010, I built a deck and installed a sunroom for a client in Bracebridge, all supported by Postech screw piles. Everything went well and the following year the owners decided to expand and incorporate a hot tub. There were only three footings needed and so I dug them by hand all according to code and poured Sonotubes rather than bothering Rob at Postech Muskoka for only 3 piles.
The next spring all three sonotubes had heaved while the piles remained in exactly the same position as the day they were installed. I will never pour another tube.